Re: [Ext2-devel] [RFC] Adding multiple block allocation

Re: [Ext2-devel] [RFC] Adding multiple block allocation

[Suparna Bhattacharya]

On Thu, Apr 28, 2005 at 12:14:24PM -0700, Mingming Cao wrote:
> Currently ext3_get_block()/ext3_new_block() only allocate one block at a
> time.  To allocate multiple blocks, the caller, for example, ext3 direct
> IO routine, has to invoke ext3_get_block() many times.  This is quite
> inefficient for sequential IO workload. 
> 
> The benefit of a real get_blocks() include
> 1) increase the possibility to get contiguous blocks, reduce possibility
> of  fragmentation due to interleaved allocations from other threads.
> (should good for non reservation case)
> 2) Reduces CPU cycles spent in repeated get_block() calls
> 3) Batch meta data update and journaling in one short
> 4) Could possibly speed up future get_blocks() look up by cache the last
> mapped blocks in inode.
> 

And here is the patch to make mpage_writepages use get_blocks() for
multiple block lookup/allocation. It performs a radix-tree contiguous 
pages lookup, and issues a get_blocks for the range together. It maintains
an mpageio structure to track intermediate mapping state, somewhat
like the DIO code.

It does need some more testing, especially block_size < PAGE_SIZE.
The JFS workaround can be dropped if the JFS get_blocks fix from
Dave Kleikamp is integrated.

Review feedback would be welcome.

Mingming,
Let me know if you have a chance to try this out with your patch.

Regards
Suparna

-- 
Suparna Bhattacharya (suparna@in.ibm.com)
Linux Technology Center
IBM Software Lab, India


diff -urp -X dontdiff linux-2.6.12-rc3/fs/buffer.c linux-2.6.12-rc3-getblocks/fs/buffer.c
--- linux-2.6.12-rc3/fs/buffer.c	2005-04-21 05:33:15.000000000 +0530
+++ linux-2.6.12-rc3-getblocks/fs/buffer.c	2005-04-22 15:08:33.000000000 +0530
@@ -2514,53 +2514,10 @@ EXPORT_SYMBOL(nobh_commit_write);
  * that it tries to operate without attaching bufferheads to
  * the page.
  */
-int nobh_writepage(struct page *page, get_block_t *get_block,
-			struct writeback_control *wbc)
+int nobh_writepage(struct page *page, get_blocks_t *get_blocks,
+		struct writeback_control *wbc, writepage_t bh_writepage_fn)
 {
-	struct inode * const inode = page->mapping->host;
-	loff_t i_size = i_size_read(inode);
-	const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
-	unsigned offset;
-	void *kaddr;
-	int ret;
-
-	/* Is the page fully inside i_size? */
-	if (page->index < end_index)
-		goto out;
-
-	/* Is the page fully outside i_size? (truncate in progress) */
-	offset = i_size & (PAGE_CACHE_SIZE-1);
-	if (page->index >= end_index+1 || !offset) {
-		/*
-		 * The page may have dirty, unmapped buffers.  For example,
-		 * they may have been added in ext3_writepage().  Make them
-		 * freeable here, so the page does not leak.
-		 */
-#if 0
-		/* Not really sure about this  - do we need this ? */
-		if (page->mapping->a_ops->invalidatepage)
-			page->mapping->a_ops->invalidatepage(page, offset);
-#endif
-		unlock_page(page);
-		return 0; /* don't care */
-	}
-
-	/*
-	 * The page straddles i_size.  It must be zeroed out on each and every
-	 * writepage invocation because it may be mmapped.  "A file is mapped
-	 * in multiples of the page size.  For a file that is not a multiple of
-	 * the  page size, the remaining memory is zeroed when mapped, and
-	 * writes to that region are not written out to the file."
-	 */
-	kaddr = kmap_atomic(page, KM_USER0);
-	memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset);
-	flush_dcache_page(page);
-	kunmap_atomic(kaddr, KM_USER0);
-out:
-	ret = mpage_writepage(page, get_block, wbc);
-	if (ret == -EAGAIN)
-		ret = __block_write_full_page(inode, page, get_block, wbc);
-	return ret;
+	return mpage_writepage(page, get_blocks, wbc, bh_writepage_fn);
 }
 EXPORT_SYMBOL(nobh_writepage);
 
diff -urp -X dontdiff linux-2.6.12-rc3/fs/ext2/inode.c linux-2.6.12-rc3-getblocks/fs/ext2/inode.c
--- linux-2.6.12-rc3/fs/ext2/inode.c	2005-04-21 05:33:15.000000000 +0530
+++ linux-2.6.12-rc3-getblocks/fs/ext2/inode.c	2005-04-22 16:30:42.000000000 +0530
@@ -639,12 +639,6 @@ ext2_nobh_prepare_write(struct file *fil
 	return nobh_prepare_write(page,from,to,ext2_get_block);
 }
 
-static int ext2_nobh_writepage(struct page *page,
-			struct writeback_control *wbc)
-{
-	return nobh_writepage(page, ext2_get_block, wbc);
-}
-
 static sector_t ext2_bmap(struct address_space *mapping, sector_t block)
 {
 	return generic_block_bmap(mapping,block,ext2_get_block);
@@ -662,6 +656,12 @@ ext2_get_blocks(struct inode *inode, sec
 	return ret;
 }
 
+static int ext2_nobh_writepage(struct page *page,
+			struct writeback_control *wbc)
+{
+	return nobh_writepage(page, ext2_get_blocks, wbc, ext2_writepage);
+}
+
 static ssize_t
 ext2_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
 			loff_t offset, unsigned long nr_segs)
@@ -676,7 +676,8 @@ ext2_direct_IO(int rw, struct kiocb *ioc
 static int
 ext2_writepages(struct address_space *mapping, struct writeback_control *wbc)
 {
-	return mpage_writepages(mapping, wbc, ext2_get_block);
+        return __mpage_writepages(mapping, wbc, ext2_get_blocks,
+					ext2_writepage);
 }
 
 struct address_space_operations ext2_aops = {
diff -urp -X dontdiff linux-2.6.12-rc3/fs/ext3/inode.c linux-2.6.12-rc3-getblocks/fs/ext3/inode.c
--- linux-2.6.12-rc3/fs/ext3/inode.c	2005-04-21 05:33:15.000000000 +0530
+++ linux-2.6.12-rc3-getblocks/fs/ext3/inode.c	2005-04-22 15:08:33.000000000 +0530
@@ -866,10 +866,10 @@ get_block:
 	return ret;
 }
 
-static int ext3_writepages_get_block(struct inode *inode, sector_t iblock,
-			struct buffer_head *bh, int create)
+static int ext3_writepages_get_blocks(struct inode *inode, sector_t iblock,
+		unsigned long max_blocks, struct buffer_head *bh, int create)
 {
-	return ext3_direct_io_get_blocks(inode, iblock, 1, bh, create);
+	return ext3_direct_io_get_blocks(inode, iblock, max_blocks, bh, create);
 }
 
 /*
@@ -1369,11 +1369,11 @@ ext3_writeback_writepages(struct address
 		return ret;
 	}
 
-        ret = __mpage_writepages(mapping, wbc, ext3_writepages_get_block,
+        ret = __mpage_writepages(mapping, wbc, ext3_writepages_get_blocks,
 					ext3_writeback_writepage_helper);
 
 	/*
-	 * Need to reaquire the handle since ext3_writepages_get_block()
+	 * Need to reaquire the handle since ext3_writepages_get_blocks()
 	 * can restart the handle
 	 */
 	handle = journal_current_handle();
@@ -1402,7 +1402,8 @@ static int ext3_writeback_writepage(stru
 	}
 
 	if (test_opt(inode->i_sb, NOBH))
-		ret = nobh_writepage(page, ext3_get_block, wbc);
+		ret = nobh_writepage(page, ext3_writepages_get_blocks, wbc,
+			ext3_writeback_writepage_helper);
 	else
 		ret = block_write_full_page(page, ext3_get_block, wbc);
 
diff -urp -X dontdiff linux-2.6.12-rc3/fs/ext3/super.c linux-2.6.12-rc3-getblocks/fs/ext3/super.c
--- linux-2.6.12-rc3/fs/ext3/super.c	2005-04-21 05:33:15.000000000 +0530
+++ linux-2.6.12-rc3-getblocks/fs/ext3/super.c	2005-04-22 15:08:33.000000000 +0530
@@ -1321,6 +1321,7 @@ static int ext3_fill_super (struct super
 	sbi->s_resgid = le16_to_cpu(es->s_def_resgid);
 
 	set_opt(sbi->s_mount_opt, RESERVATION);
+	set_opt(sbi->s_mount_opt, NOBH); /* temp: set nobh default */
 
 	if (!parse_options ((char *) data, sb, &journal_inum, NULL, 0))
 		goto failed_mount;
@@ -1567,6 +1568,7 @@ static int ext3_fill_super (struct super
 			printk(KERN_ERR "EXT3-fs: Journal does not support "
 			       "requested data journaling mode\n");
 			goto failed_mount3;
+		set_opt(sbi->s_mount_opt, NOBH); /* temp: set nobh default */
 		}
 	default:
 		break;
@@ -1584,6 +1586,7 @@ static int ext3_fill_super (struct super
 				"its supported only with writeback mode\n");
 			clear_opt(sbi->s_mount_opt, NOBH);
 		}
+		printk("NOBH option set\n");
 	}
 	/*
 	 * The journal_load will have done any necessary log recovery,
diff -urp -X dontdiff linux-2.6.12-rc3/fs/hfs/inode.c linux-2.6.12-rc3-getblocks/fs/hfs/inode.c
--- linux-2.6.12-rc3/fs/hfs/inode.c	2005-04-21 05:33:15.000000000 +0530
+++ linux-2.6.12-rc3-getblocks/fs/hfs/inode.c	2005-04-22 15:08:33.000000000 +0530
@@ -124,7 +124,7 @@ static ssize_t hfs_direct_IO(int rw, str
 static int hfs_writepages(struct address_space *mapping,
 			  struct writeback_control *wbc)
 {
-	return mpage_writepages(mapping, wbc, hfs_get_block);
+	return mpage_writepages(mapping, wbc, hfs_get_blocks);
 }
 
 struct address_space_operations hfs_btree_aops = {
diff -urp -X dontdiff linux-2.6.12-rc3/fs/hfsplus/inode.c linux-2.6.12-rc3-getblocks/fs/hfsplus/inode.c
--- linux-2.6.12-rc3/fs/hfsplus/inode.c	2005-04-21 05:33:15.000000000 +0530
+++ linux-2.6.12-rc3-getblocks/fs/hfsplus/inode.c	2005-04-22 15:08:33.000000000 +0530
@@ -121,7 +121,7 @@ static ssize_t hfsplus_direct_IO(int rw,
 static int hfsplus_writepages(struct address_space *mapping,
 			      struct writeback_control *wbc)
 {
-	return mpage_writepages(mapping, wbc, hfsplus_get_block);
+	return mpage_writepages(mapping, wbc, hfsplus_get_blocks);
 }
 
 struct address_space_operations hfsplus_btree_aops = {
diff -urp -X dontdiff linux-2.6.12-rc3/fs/jfs/inode.c linux-2.6.12-rc3-getblocks/fs/jfs/inode.c
--- linux-2.6.12-rc3/fs/jfs/inode.c	2005-04-21 05:33:15.000000000 +0530
+++ linux-2.6.12-rc3-getblocks/fs/jfs/inode.c	2005-04-22 16:27:19.000000000 +0530
@@ -267,21 +267,41 @@ jfs_get_blocks(struct inode *ip, sector_
 	return rc;
 }
 
+static int
+jfs_mpage_get_blocks(struct inode *ip, sector_t lblock, unsigned long
+			max_blocks, struct buffer_head *bh_result, int create)
+{
+	/* 
+	 * fixme: temporary workaround: return one block at a time until
+	 * we figure out why we see exposures with truncate on 
+	 * allocating multiple blocks in one shot.
+	 */
+	return jfs_get_blocks(ip, lblock, 1, bh_result, create);
+}
+
 static int jfs_get_block(struct inode *ip, sector_t lblock,
 			 struct buffer_head *bh_result, int create)
 {
 	return jfs_get_blocks(ip, lblock, 1, bh_result, create);
 }
 
+static int jfs_bh_writepage(struct page *page,
+				struct writeback_control *wbc)
+{
+	return block_write_full_page(page, jfs_get_block, wbc);
+}
+
+
 static int jfs_writepage(struct page *page, struct writeback_control *wbc)
 {
-	return nobh_writepage(page, jfs_get_block, wbc);
+	return nobh_writepage(page, jfs_mpage_get_blocks, wbc, jfs_bh_writepage);
 }
 
 static int jfs_writepages(struct address_space *mapping,
 			struct writeback_control *wbc)
 {
-	return mpage_writepages(mapping, wbc, jfs_get_block);
+        return __mpage_writepages(mapping, wbc, jfs_mpage_get_blocks,
+					jfs_bh_writepage);
 }
 
 static int jfs_readpage(struct file *file, struct page *page)
diff -urp -X dontdiff linux-2.6.12-rc3/fs/mpage.c linux-2.6.12-rc3-getblocks/fs/mpage.c
--- linux-2.6.12-rc3/fs/mpage.c	2005-04-21 05:33:15.000000000 +0530
+++ linux-2.6.12-rc3-getblocks/fs/mpage.c	2005-04-22 16:19:14.000000000 +0530
@@ -370,6 +370,67 @@ int mpage_readpage(struct page *page, ge
 }
 EXPORT_SYMBOL(mpage_readpage);
 
+struct mpageio {
+	struct bio *bio;
+	struct buffer_head map_bh;
+	unsigned long block_in_file;
+	unsigned long final_block_in_request;
+	sector_t long block_in_bio;
+	int boundary;
+	sector_t boundary_block;
+	struct block_device *boundary_bdev;
+};
+
+/*
+ * Maps as many contiguous disk blocks as it can within the range of
+ * the request, and returns the total number of contiguous mapped
+ * blocks in the mpageio.
+ */
+static unsigned long mpage_get_more_blocks(struct mpageio *mio,
+	struct inode *inode, get_blocks_t get_blocks)
+{
+	struct buffer_head map_bh = {.b_state = 0};
+	unsigned long mio_nblocks = mio->map_bh.b_size >> inode->i_blkbits;
+	unsigned long first_unmapped = mio->block_in_file + mio_nblocks;
+	unsigned long next_contig_block = mio->map_bh.b_blocknr + mio_nblocks;
+
+	while ((first_unmapped < mio->final_block_in_request) &&
+		(mio->map_bh.b_size < PAGE_SIZE)) {
+
+		if (get_blocks(inode, first_unmapped,
+			mio->final_block_in_request - first_unmapped,
+			&map_bh, 1))
+			break;
+		if (mio_nblocks && ((map_bh.b_blocknr != next_contig_block) ||
+			map_bh.b_bdev != mio->map_bh.b_bdev))
+			break;
+			
+		if (buffer_new(&map_bh)) {
+			int i = 0;
+			for (; i < map_bh.b_size >> inode->i_blkbits; i++)
+				unmap_underlying_metadata(map_bh.b_bdev,
+					map_bh.b_blocknr + i);
+		}
+		
+		if (buffer_boundary(&map_bh)) {
+			mio->boundary = 1;
+			mio->boundary_block = map_bh.b_blocknr;
+			mio->boundary_bdev = map_bh.b_bdev;
+		}
+		if (mio_nblocks == 0) {
+			mio->map_bh.b_bdev = map_bh.b_bdev;
+			mio->map_bh.b_blocknr = map_bh.b_blocknr;
+		}
+
+		mio_nblocks += map_bh.b_size >> inode->i_blkbits;
+		first_unmapped = mio->block_in_file + mio_nblocks;
+		next_contig_block = mio->map_bh.b_blocknr + mio_nblocks;
+		mio->map_bh.b_size += map_bh.b_size;
+	}
+
+	return mio_nblocks;
+}
+
 /*
  * Writing is not so simple.
  *
@@ -386,9 +447,9 @@ EXPORT_SYMBOL(mpage_readpage);
  * written, so it can intelligently allocate a suitably-sized BIO.  For now,
  * just allocate full-size (16-page) BIOs.
  */
-static struct bio *
-__mpage_writepage(struct bio *bio, struct page *page, get_block_t get_block,
-	sector_t *last_block_in_bio, int *ret, struct writeback_control *wbc,
+static int
+__mpage_writepage(struct mpageio *mio, struct page *page,
+	get_blocks_t get_blocks, struct writeback_control *wbc,
 	writepage_t writepage_fn)
 {
 	struct address_space *mapping = page->mapping;
@@ -396,9 +457,8 @@ __mpage_writepage(struct bio *bio, struc
 	const unsigned blkbits = inode->i_blkbits;
 	unsigned long end_index;
 	const unsigned blocks_per_page = PAGE_CACHE_SIZE >> blkbits;
-	sector_t last_block;
+	sector_t last_block, blocks_to_skip;
 	sector_t block_in_file;
-	sector_t blocks[MAX_BUF_PER_PAGE];
 	unsigned page_block;
 	unsigned first_unmapped = blocks_per_page;
 	struct block_device *bdev = NULL;
@@ -406,8 +466,10 @@ __mpage_writepage(struct bio *bio, struc
 	sector_t boundary_block = 0;
 	struct block_device *boundary_bdev = NULL;
 	int length;
-	struct buffer_head map_bh;
 	loff_t i_size = i_size_read(inode);
+	struct buffer_head *map_bh = &mio->map_bh;
+	struct bio *bio = mio->bio;
+	int ret = 0;
 
 	if (page_has_buffers(page)) {
 		struct buffer_head *head = page_buffers(page);
@@ -435,10 +497,13 @@ __mpage_writepage(struct bio *bio, struc
 			if (!buffer_dirty(bh) || !buffer_uptodate(bh))
 				goto confused;
 			if (page_block) {
-				if (bh->b_blocknr != blocks[page_block-1] + 1)
+				if (bh->b_blocknr != map_bh->b_blocknr 
+					+ page_block)
 					goto confused;
+			} else {
+				map_bh->b_blocknr = bh->b_blocknr;
+				map_bh->b_size = PAGE_SIZE;
 			}
-			blocks[page_block++] = bh->b_blocknr;
 			boundary = buffer_boundary(bh);
 			if (boundary) {
 				boundary_block = bh->b_blocknr;
@@ -465,33 +530,30 @@ __mpage_writepage(struct bio *bio, struc
 	BUG_ON(!PageUptodate(page));
 	block_in_file = page->index << (PAGE_CACHE_SHIFT - blkbits);
 	last_block = (i_size - 1) >> blkbits;
-	map_bh.b_page = page;
-	for (page_block = 0; page_block < blocks_per_page; ) {
-
-		map_bh.b_state = 0;
-		if (get_block(inode, block_in_file, &map_bh, 1))
-			goto confused;
-		if (buffer_new(&map_bh))
-			unmap_underlying_metadata(map_bh.b_bdev,
-						map_bh.b_blocknr);
-		if (buffer_boundary(&map_bh)) {
-			boundary_block = map_bh.b_blocknr;
-			boundary_bdev = map_bh.b_bdev;
-		}
-		if (page_block) {
-			if (map_bh.b_blocknr != blocks[page_block-1] + 1)
-				goto confused;
-		}
-		blocks[page_block++] = map_bh.b_blocknr;
-		boundary = buffer_boundary(&map_bh);
-		bdev = map_bh.b_bdev;
-		if (block_in_file == last_block)
-			break;
-		block_in_file++;
+	blocks_to_skip = block_in_file - mio->block_in_file;
+	mio->block_in_file = block_in_file;
+	if (blocks_to_skip < (map_bh->b_size >> blkbits)) {
+		map_bh->b_blocknr += blocks_to_skip;
+		map_bh->b_size -= blocks_to_skip << blkbits;
+	} else {
+		map_bh->b_state = 0;
+		map_bh->b_size = 0;
+		if (mio->final_block_in_request > last_block)
+			mio->final_block_in_request = last_block;
+		mpage_get_more_blocks(mio, inode, get_blocks);
 	}
-	BUG_ON(page_block == 0);
+	if (map_bh->b_size < PAGE_SIZE)
+		goto confused;
 
-	first_unmapped = page_block;
+	if (mio->boundary && (mio->boundary_block < map_bh->b_blocknr 
+		+ blocks_per_page)) {
+		boundary = 1;
+		boundary_block = mio->boundary_block;
+		boundary_bdev = mio->boundary_bdev;
+	}
+		
+	bdev = map_bh->b_bdev;
+	first_unmapped = blocks_per_page;
 
 page_is_mapped:
 	end_index = i_size >> PAGE_CACHE_SHIFT;
@@ -518,12 +580,16 @@ page_is_mapped:
 	/*
 	 * This page will go to BIO.  Do we need to send this BIO off first?
 	 */
-	if (bio && *last_block_in_bio != blocks[0] - 1)
+	if (bio && mio->block_in_bio != map_bh->b_blocknr - 1)
 		bio = mpage_bio_submit(WRITE, bio);
 
 alloc_new:
 	if (bio == NULL) {
-		bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9),
+		/* 
+		 * Fixme: bio size can be limited to final_block - block, or
+		 * even mio->map_bh.b_size
+		 */
+		bio = mpage_alloc(bdev, map_bh->b_blocknr << (blkbits - 9),
 				bio_get_nr_vecs(bdev), GFP_NOFS|__GFP_HIGH);
 		if (bio == NULL)
 			goto confused;
@@ -539,6 +605,9 @@ alloc_new:
 		bio = mpage_bio_submit(WRITE, bio);
 		goto alloc_new;
 	}
+	map_bh->b_blocknr += blocks_per_page;
+	map_bh->b_size -= PAGE_SIZE;
+	mio->block_in_file += blocks_per_page;
 
 	/*
 	 * OK, we have our BIO, so we can now mark the buffers clean.  Make
@@ -575,7 +644,8 @@ alloc_new:
 					boundary_block, 1 << blkbits);
 		}
 	} else {
-		*last_block_in_bio = blocks[blocks_per_page - 1];
+		/* we can pack more pages into the bio, don't submit yet */
+		mio->block_in_bio = map_bh->b_blocknr - 1;
 	}
 	goto out;
 
@@ -584,22 +654,23 @@ confused:
 		bio = mpage_bio_submit(WRITE, bio);
 
 	if (writepage_fn) {
-		*ret = (*writepage_fn)(page, wbc);
+		ret = (*writepage_fn)(page, wbc);
 	} else {
-		*ret = -EAGAIN;
+		ret = -EAGAIN;
 		goto out;
 	}
 	/*
 	 * The caller has a ref on the inode, so *mapping is stable
 	 */
-	if (*ret) {
-		if (*ret == -ENOSPC)
+	if (ret) {
+		if (ret == -ENOSPC)
 			set_bit(AS_ENOSPC, &mapping->flags);
 		else
 			set_bit(AS_EIO, &mapping->flags);
 	}
 out:
-	return bio;
+	mio->bio = bio;
+	return ret;
 }
 
 /**
@@ -625,20 +696,21 @@ out:
  */
 int
 mpage_writepages(struct address_space *mapping,
-		struct writeback_control *wbc, get_block_t get_block)
+		struct writeback_control *wbc, get_blocks_t get_blocks)
 {
-	return __mpage_writepages(mapping, wbc, get_block,
+	return __mpage_writepages(mapping, wbc, get_blocks,
 		mapping->a_ops->writepage);
 }
 
 int
 __mpage_writepages(struct address_space *mapping,
-		struct writeback_control *wbc, get_block_t get_block,
+		struct writeback_control *wbc, get_blocks_t get_blocks,
 		writepage_t writepage_fn)
 {
 	struct backing_dev_info *bdi = mapping->backing_dev_info;
+	struct inode *inode = mapping->host;
+	const unsigned blkbits = inode->i_blkbits;
 	struct bio *bio = NULL;
-	sector_t last_block_in_bio = 0;
 	int ret = 0;
 	int done = 0;
 	int (*writepage)(struct page *page, struct writeback_control *wbc);
@@ -648,6 +720,9 @@ __mpage_writepages(struct address_space 
 	pgoff_t end = -1;		/* Inclusive */
 	int scanned = 0;
 	int is_range = 0;
+	struct mpageio mio = {
+		.bio = NULL
+	};
 
 	if (wbc->nonblocking && bdi_write_congested(bdi)) {
 		wbc->encountered_congestion = 1;
@@ -655,7 +730,7 @@ __mpage_writepages(struct address_space 
 	}
 
 	writepage = NULL;
-	if (get_block == NULL)
+	if (get_blocks == NULL)
 		writepage = mapping->a_ops->writepage;
 
 	pagevec_init(&pvec, 0);
@@ -672,12 +747,15 @@ __mpage_writepages(struct address_space 
 		scanned = 1;
 	}
 retry:
+	down_read(&inode->i_alloc_sem);
 	while (!done && (index <= end) &&
-			(nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
-			PAGECACHE_TAG_DIRTY,
+			(nr_pages = pagevec_contig_lookup_tag(&pvec, mapping,
+			&index, PAGECACHE_TAG_DIRTY,
 			min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1))) {
 		unsigned i;
 
+		mio.final_block_in_request = min(index, end) <<
+			(PAGE_CACHE_SHIFT - blkbits);
 		scanned = 1;
 		for (i = 0; i < nr_pages; i++) {
 			struct page *page = pvec.pages[i];
@@ -702,7 +780,7 @@ retry:
 				unlock_page(page);
 				continue;
 			}
-
+			
 			if (wbc->sync_mode != WB_SYNC_NONE)
 				wait_on_page_writeback(page);
 
@@ -723,9 +801,9 @@ retry:
 							&mapping->flags);
 				}
 			} else {
-				bio = __mpage_writepage(bio, page, get_block,
-						&last_block_in_bio, &ret, wbc,
-						writepage_fn);
+				ret = __mpage_writepage(&mio, page, get_blocks,
+						wbc, writepage_fn);
+				bio = mio.bio;
 			}
 			if (ret || (--(wbc->nr_to_write) <= 0))
 				done = 1;
@@ -737,6 +815,9 @@ retry:
 		pagevec_release(&pvec);
 		cond_resched();
 	}
+	
+	up_read(&inode->i_alloc_sem);
+
 	if (!scanned && !done) {
 		/*
 		 * We hit the last page and there is more work to be done: wrap
@@ -755,17 +836,23 @@ retry:
 EXPORT_SYMBOL(mpage_writepages);
 EXPORT_SYMBOL(__mpage_writepages);
 
-int mpage_writepage(struct page *page, get_block_t get_block,
-	struct writeback_control *wbc)
+int mpage_writepage(struct page *page, get_blocks_t get_blocks,
+		struct writeback_control *wbc, writepage_t writepage_fn)
 {
 	int ret = 0;
-	struct bio *bio;
-	sector_t last_block_in_bio = 0;
-
-	bio = __mpage_writepage(NULL, page, get_block,
-			&last_block_in_bio, &ret, wbc, NULL);
-	if (bio)
-		mpage_bio_submit(WRITE, bio);
+	struct address_space *mapping = page->mapping;
+	struct inode *inode = mapping->host;
+	const unsigned blkbits = inode->i_blkbits;
+	struct mpageio mio = {
+		.final_block_in_request = (page->index + 1) << (PAGE_CACHE_SHIFT
+			- blkbits)
+	};
+
+	dump_stack();
+	ret = __mpage_writepage(&mio, page, get_blocks,
+			wbc, writepage_fn);
+	if (mio.bio)
+		mpage_bio_submit(WRITE, mio.bio);
 
 	return ret;
 }
diff -urp -X dontdiff linux-2.6.12-rc3/include/linux/buffer_head.h linux-2.6.12-rc3-getblocks/include/linux/buffer_head.h
--- linux-2.6.12-rc3/include/linux/buffer_head.h	2005-04-21 05:33:16.000000000 +0530
+++ linux-2.6.12-rc3-getblocks/include/linux/buffer_head.h	2005-04-22 15:08:33.000000000 +0530
@@ -203,8 +203,8 @@ int file_fsync(struct file *, struct den
 int nobh_prepare_write(struct page*, unsigned, unsigned, get_block_t*);
 int nobh_commit_write(struct file *, struct page *, unsigned, unsigned);
 int nobh_truncate_page(struct address_space *, loff_t);
-int nobh_writepage(struct page *page, get_block_t *get_block,
-                        struct writeback_control *wbc);
+int nobh_writepage(struct page *page, get_blocks_t *get_blocks,
+	struct writeback_control *wbc, writepage_t bh_writepage);
 
 
 /*
diff -urp -X dontdiff linux-2.6.12-rc3/include/linux/fs.h linux-2.6.12-rc3-getblocks/include/linux/fs.h
--- linux-2.6.12-rc3/include/linux/fs.h	2005-04-21 05:33:16.000000000 +0530
+++ linux-2.6.12-rc3-getblocks/include/linux/fs.h	2005-04-22 15:08:33.000000000 +0530
@@ -304,6 +304,8 @@ struct address_space;
 struct writeback_control;
 struct kiocb;
 
+typedef int (writepage_t)(struct page *page, struct writeback_control *wbc);
+
 struct address_space_operations {
 	int (*writepage)(struct page *page, struct writeback_control *wbc);
 	int (*readpage)(struct file *, struct page *);
diff -urp -X dontdiff linux-2.6.12-rc3/include/linux/mpage.h linux-2.6.12-rc3-getblocks/include/linux/mpage.h
--- linux-2.6.12-rc3/include/linux/mpage.h	2005-04-21 05:33:16.000000000 +0530
+++ linux-2.6.12-rc3-getblocks/include/linux/mpage.h	2005-04-22 15:08:33.000000000 +0530
@@ -11,17 +11,16 @@
  */
 
 struct writeback_control;
-typedef int (writepage_t)(struct page *page, struct writeback_control *wbc);
 
 int mpage_readpages(struct address_space *mapping, struct list_head *pages,
 				unsigned nr_pages, get_block_t get_block);
 int mpage_readpage(struct page *page, get_block_t get_block);
 int mpage_writepages(struct address_space *mapping,
-		struct writeback_control *wbc, get_block_t get_block);
-int mpage_writepage(struct page *page, get_block_t *get_block,
-		struct writeback_control *wbc);
+		struct writeback_control *wbc, get_blocks_t get_blocks);
+int mpage_writepage(struct page *page, get_blocks_t *get_blocks,
+		struct writeback_control *wbc, writepage_t writepage);
 int __mpage_writepages(struct address_space *mapping,
-		struct writeback_control *wbc, get_block_t get_block,
+		struct writeback_control *wbc, get_blocks_t get_blocks,
 		writepage_t writepage);
 
 static inline int
diff -urp -X dontdiff linux-2.6.12-rc3/include/linux/pagemap.h linux-2.6.12-rc3-getblocks/include/linux/pagemap.h
--- linux-2.6.12-rc3/include/linux/pagemap.h	2005-04-21 05:33:16.000000000 +0530
+++ linux-2.6.12-rc3-getblocks/include/linux/pagemap.h	2005-04-22 15:08:33.000000000 +0530
@@ -73,7 +73,8 @@ extern struct page * find_or_create_page
 unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
 			unsigned int nr_pages, struct page **pages);
 unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
-			int tag, unsigned int nr_pages, struct page **pages);
+			int tag, unsigned int nr_pages, struct page **pages,
+			int contig);
 
 /*
  * Returns locked page at given index in given cache, creating it if needed.
diff -urp -X dontdiff linux-2.6.12-rc3/include/linux/pagevec.h linux-2.6.12-rc3-getblocks/include/linux/pagevec.h
--- linux-2.6.12-rc3/include/linux/pagevec.h	2005-04-21 05:33:16.000000000 +0530
+++ linux-2.6.12-rc3-getblocks/include/linux/pagevec.h	2005-04-22 15:08:33.000000000 +0530
@@ -28,6 +28,9 @@ unsigned pagevec_lookup(struct pagevec *
 unsigned pagevec_lookup_tag(struct pagevec *pvec,
 		struct address_space *mapping, pgoff_t *index, int tag,
 		unsigned nr_pages);
+unsigned pagevec_contig_lookup_tag(struct pagevec *pvec,
+		struct address_space *mapping, pgoff_t *index, int tag,
+		unsigned nr_pages);
 
 static inline void pagevec_init(struct pagevec *pvec, int cold)
 {
diff -urp -X dontdiff linux-2.6.12-rc3/include/linux/radix-tree.h linux-2.6.12-rc3-getblocks/include/linux/radix-tree.h
--- linux-2.6.12-rc3/include/linux/radix-tree.h	2005-04-21 05:33:16.000000000 +0530
+++ linux-2.6.12-rc3-getblocks/include/linux/radix-tree.h	2005-04-22 15:08:33.000000000 +0530
@@ -59,8 +59,18 @@ void *radix_tree_tag_clear(struct radix_
 int radix_tree_tag_get(struct radix_tree_root *root,
 			unsigned long index, int tag);
 unsigned int
-radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
-		unsigned long first_index, unsigned int max_items, int tag);
+__radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
+		unsigned long first_index, unsigned int max_items, int tag,
+		int contig);
+
+static inline unsigned int radix_tree_gang_lookup_tag(struct radix_tree_root
+		*root, void **results, unsigned long first_index,
+		unsigned int max_items, int tag)
+{
+	return __radix_tree_gang_lookup_tag(root, results, first_index,
+		max_items, tag, 0);
+}
+
 int radix_tree_tagged(struct radix_tree_root *root, int tag);
 
 static inline void radix_tree_preload_end(void)
diff -urp -X dontdiff linux-2.6.12-rc3/lib/radix-tree.c linux-2.6.12-rc3-getblocks/lib/radix-tree.c
--- linux-2.6.12-rc3/lib/radix-tree.c	2005-04-21 05:33:16.000000000 +0530
+++ linux-2.6.12-rc3-getblocks/lib/radix-tree.c	2005-04-22 16:34:29.000000000 +0530
@@ -557,12 +557,13 @@ EXPORT_SYMBOL(radix_tree_gang_lookup);
  */
 static unsigned int
 __lookup_tag(struct radix_tree_root *root, void **results, unsigned long index,
-	unsigned int max_items, unsigned long *next_index, int tag)
+	unsigned int max_items, unsigned long *next_index, int tag, int contig)
 {
 	unsigned int nr_found = 0;
 	unsigned int shift;
 	unsigned int height = root->height;
 	struct radix_tree_node *slot;
+	unsigned long cindex = (contig && (*next_index)) ? *next_index : -1;
 
 	shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
 	slot = root->rnode;
@@ -575,6 +576,11 @@ __lookup_tag(struct radix_tree_root *roo
 				BUG_ON(slot->slots[i] == NULL);
 				break;
 			}
+			if (contig && index >= cindex) {
+				/* break in contiguity */
+				index = 0;
+				goto out;
+			}
 			index &= ~((1UL << shift) - 1);
 			index += 1UL << shift;
 			if (index == 0)
@@ -593,6 +599,10 @@ __lookup_tag(struct radix_tree_root *roo
 					results[nr_found++] = slot->slots[j];
 					if (nr_found == max_items)
 						goto out;
+				} else if (contig && nr_found) {
+					/* break in contiguity */
+					index = 0;
+					goto out;
 				}
 			}
 		}
@@ -618,29 +628,32 @@ out:
  *	returns the number of items which were placed at *@results.
  */
 unsigned int
-radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
-		unsigned long first_index, unsigned int max_items, int tag)
+__radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
+		unsigned long first_index, unsigned int max_items, int tag,
+		int contig)
 {
 	const unsigned long max_index = radix_tree_maxindex(root->height);
 	unsigned long cur_index = first_index;
+	unsigned long next_index = 0;	/* Index of next contiguous search */
 	unsigned int ret = 0;
 
 	while (ret < max_items) {
 		unsigned int nr_found;
-		unsigned long next_index;	/* Index of next search */
 
 		if (cur_index > max_index)
 			break;
 		nr_found = __lookup_tag(root, results + ret, cur_index,
-					max_items - ret, &next_index, tag);
+				max_items - ret, &next_index, tag, contig);
 		ret += nr_found;
 		if (next_index == 0)
 			break;
 		cur_index = next_index;
+		if (!nr_found)
+			next_index = 0;
 	}
 	return ret;
 }
-EXPORT_SYMBOL(radix_tree_gang_lookup_tag);
+EXPORT_SYMBOL(__radix_tree_gang_lookup_tag);
 
 /**
  *	radix_tree_delete    -    delete an item from a radix tree
diff -urp -X dontdiff linux-2.6.12-rc3/mm/filemap.c linux-2.6.12-rc3-getblocks/mm/filemap.c
--- linux-2.6.12-rc3/mm/filemap.c	2005-04-21 05:33:16.000000000 +0530
+++ linux-2.6.12-rc3-getblocks/mm/filemap.c	2005-04-22 16:20:30.000000000 +0530
@@ -635,16 +635,19 @@ unsigned find_get_pages(struct address_s
 /*
  * Like find_get_pages, except we only return pages which are tagged with
  * `tag'.   We update *index to index the next page for the traversal.
+ * If 'contig' is 1, then we return only pages which are contiguous in the
+ * file.
  */
 unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
-			int tag, unsigned int nr_pages, struct page **pages)
+			int tag, unsigned int nr_pages, struct page **pages,
+			int contig)
 {
 	unsigned int i;
 	unsigned int ret;
 
 	read_lock_irq(&mapping->tree_lock);
-	ret = radix_tree_gang_lookup_tag(&mapping->page_tree,
-				(void **)pages, *index, nr_pages, tag);
+	ret = __radix_tree_gang_lookup_tag(&mapping->page_tree,
+			(void **)pages, *index, nr_pages, tag, contig);
 	for (i = 0; i < ret; i++)
 		page_cache_get(pages[i]);
 	if (ret)
diff -urp -X dontdiff linux-2.6.12-rc3/mm/swap.c linux-2.6.12-rc3-getblocks/mm/swap.c
--- linux-2.6.12-rc3/mm/swap.c	2005-04-21 05:33:16.000000000 +0530
+++ linux-2.6.12-rc3-getblocks/mm/swap.c	2005-04-22 15:08:33.000000000 +0530
@@ -384,7 +384,16 @@ unsigned pagevec_lookup_tag(struct pagev
 		pgoff_t *index, int tag, unsigned nr_pages)
 {
 	pvec->nr = find_get_pages_tag(mapping, index, tag,
-					nr_pages, pvec->pages);
+					nr_pages, pvec->pages, 0);
+	return pagevec_count(pvec);
+}
+
+unsigned int
+pagevec_contig_lookup_tag(struct pagevec *pvec, struct address_space *mapping,
+		pgoff_t *index, int tag, unsigned nr_pages)
+{
+	pvec->nr = find_get_pages_tag(mapping, index, tag,
+					nr_pages, pvec->pages, 1);
 	return pagevec_count(pvec);
 }
 

Re: [Ext2-devel] [RFC] Adding multiple block allocation

[Mingming Cao]

On Fri, 2005-04-29 at 19:22 +0530, Suparna Bhattacharya wrote:
> On Thu, Apr 28, 2005 at 12:14:24PM -0700, Mingming Cao wrote:
> > Currently ext3_get_block()/ext3_new_block() only allocate one block at a
> > time.  To allocate multiple blocks, the caller, for example, ext3 direct
> > IO routine, has to invoke ext3_get_block() many times.  This is quite
> > inefficient for sequential IO workload. 
> > 
> > The benefit of a real get_blocks() include
> > 1) increase the possibility to get contiguous blocks, reduce possibility
> > of  fragmentation due to interleaved allocations from other threads.
> > (should good for non reservation case)
> > 2) Reduces CPU cycles spent in repeated get_block() calls
> > 3) Batch meta data update and journaling in one short
> > 4) Could possibly speed up future get_blocks() look up by cache the last
> > mapped blocks in inode.
> > 
> 
> And here is the patch to make mpage_writepages use get_blocks() for
> multiple block lookup/allocation. It performs a radix-tree contiguous 
> pages lookup, and issues a get_blocks for the range together. It maintains
> an mpageio structure to track intermediate mapping state, somewhat
> like the DIO code.
> 
> It does need some more testing, especially block_size < PAGE_SIZE.
> The JFS workaround can be dropped if the JFS get_blocks fix from
> Dave Kleikamp is integrated.
> 
> Review feedback would be welcome.
> 
> Mingming,
> Let me know if you have a chance to try this out with your patch.


Sure, Suparna, I will try your patch soon!

In my patch,  I have modified ext3 directo io code to make use of
ext3_get_blocks(). Tested with a simple file write with O_DIRECT, seems
work fine! Allocating blocks for a 120k file only invokes
ext3_get_blocks() for 4 times(perfect is 1, but before is 30 times call
to ext3_get_block). Among the 4 calls to ext3_get_blocks, 2 because of
reach the meta data block boundary(direct ->indirect), another 2 because
of reach the end of the reservation window. For the later 2, we could
avoid that by extend the reservation window before calling
ext3_new_blocks() if the window size is less than the number of blocks
to allocate.

But if it try to allocating blocks in the hole (with direct IO), blocks
are allocated one by one. I am looking at it right now.

Thanks,
Mingming

Re: [Ext2-devel] [RFC] Adding multiple block allocation

[Mingming Cao]

On Fri, 2005-04-29 at 10:10 -0700, Mingming Cao wrote:
> But if it try to allocating blocks in the hole (with direct IO), blocks
> are allocated one by one. I am looking at it right now.
> 
Hi Andrew, Badari,

If we do direct write(block allocation) to a hole, I found that the
"create" flag passed to ext3_direct_io_get_blocks() is 0 if we are
trying to _write_ to a file hole. Is this expected? 

This is what happened on mainline 2.6.12-rc2(and with my patch). To simplify, here is the problem description on mainline:

If we do 30 blocks write to a new file at offset 800k, fine, create flag is all 1. 
Then if seek back to offset 400k, write another 30 blocks, create flag is 0

-bash-2.05b# mount -t ext3 /dev/ubdc /mnt/ext3
-bash-2.05b# cd /mnt/ext3
-bash-2.05b# touch a
-bash-2.05b# /root/filetst -o 819200 -b 122880 -c 1 -w -d -f a
Calling ext3_get_block_handle from ext3_direct_io_get_blocks: maxblocks = 30, iblock = 200, create = 1
Calling ext3_get_block_handle from ext3_direct_io_get_blocks: maxblocks = 29, iblock = 201, create = 1
Calling ext3_get_block_handle from ext3_direct_io_get_blocks: maxblocks = 28, iblock = 202, create = 1
Calling ext3_get_block_handle from ext3_direct_io_get_blocks: maxblocks = 27, iblock = 203, create = 1
Calling ext3_get_block_handle from ext3_direct_io_get_blocks: maxblocks = 26, iblock = 204, create = 1
...................
Calling ext3_get_block_handle from ext3_direct_io_get_blocks: maxblocks = 5, iblock = 225, create = 1
Calling ext3_get_block_handle from ext3_direct_io_get_blocks: maxblocks = 4, iblock = 226, create = 1
Calling ext3_get_block_handle from ext3_direct_io_get_blocks: maxblocks = 3, iblock = 227, create = 1
Calling ext3_get_block_handle from ext3_direct_io_get_blocks: maxblocks = 2, iblock = 228, create = 1
Calling ext3_get_block_handle from ext3_direct_io_get_blocks: maxblocks = 1, iblock = 229, create = 1

-bash-2.05b# /root/filetst -o 409600 -b 122880 -c 1 -w -d -f a
Calling ext3_get_block_handle from ext3_direct_io_get_blocks: maxblocks = 30, iblock = 100, create = 0


Because of create flag is 0, ext3_get_block will not do block allocation
and return immediately after look up failed. Then ext3_get_block_handle
() is called from other path(I am not sure where) other than
ext3_direct_io_get_blocks to allocate the desired 30 blocks.(thus, when
apply ext3_get_blocks patch, ext3_get_blocks is not called)

Could you clarify?

Thanks,
Mingming

Re: [RFC] Adding multiple block allocation

[Andrew Morton]

Mingming Cao <cmm@us.ibm.com> wrote:
>
> If we do direct write(block allocation) to a hole, I found that the
>  "create" flag passed to ext3_direct_io_get_blocks() is 0 if we are
>  trying to _write_ to a file hole. Is this expected? 

Nope.  The code in get_more_blocks() is pretty explicit.

> But if it try to allocating blocks in the hole (with direct IO), blocks
> are allocated one by one. I am looking at it right now.
> 

Please see the comment over get_more_blocks().


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Re: [RFC] Adding multiple block allocation

[Mingming Cao]

On Fri, 2005-04-29 at 13:57 -0700, Andrew Morton wrote:
> Mingming Cao <cmm@us.ibm.com> wrote:
> >
> > If we do direct write(block allocation) to a hole, I found that the
> >  "create" flag passed to ext3_direct_io_get_blocks() is 0 if we are
> >  trying to _write_ to a file hole. Is this expected? 
> 
> Nope.  The code in get_more_blocks() is pretty explicit.
> 
> > But if it try to allocating blocks in the hole (with direct IO), blocks
> > are allocated one by one. I am looking at it right now.
> > 
> 
> Please see the comment over get_more_blocks().
> 

I went to look at get_more_blocks, the create flag is cleared if the
file offset is less than the i_size. (see code below). 

static int get_more_blocks(struct dio *dio)
{
	..........
	.........
             create = dio->rw == WRITE;
             if (dio->lock_type == DIO_LOCKING) {
                  if (dio->block_in_file < (i_size_read(dio->inode) >>
                                                       dio->blkbits))
                         create = 0;
             } else if (dio->lock_type == DIO_NO_LOCKING) {
                    create = 0;

	     ret = (*dio->get_blocks)(dio->inode, fs_startblk, fs_count,
                                                map_bh, create);

}

When it is trying to direct writing to a hole, the create flag is
cleared so that the underlying filesystem get_blocks() function will
only do a block look up(look up will be failed and no block allocation).

do_direct_IO -> get_more_blocks -> ext3_direct_io_get_blocks. In
get_more_blocks(),  do_direct_IO() handles the write to hole situation
by simply return an error of ENOTBLK. In direct_io_worker() it detects
this error then just simply return the size of written byte to 0. The
real write is handled by the buffered I/O. In
__generic_file_aio_write_nolock(), generic_file_buffered_write() will be
called if written by generic_file_direct_write() is 0.

Could you confirm my observation above?  Hope I understand this right:
right now direct io write to a hole is actually handled by buffered IO.
If so, there must be some valid reason that I could not see now.


Thanks,
Mingming



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Re: [RFC] Adding multiple block allocation

[Andrew Morton]

Mingming Cao <cmm@us.ibm.com> wrote:
>
>  right now direct io write to a hole is actually handled by buffered IO.
>  If so, there must be some valid reason that I could not see now.

Oh yes, that's right.  It's all to do with the fixes which went in a year
ago to prevent concurrent readers from peeking at uninitialised disk
blocks.



-------------------------------------------------------
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Re: [Ext2-devel] [RFC] Adding multiple block allocation

[Suparna Bhattacharya]

On Fri, Apr 29, 2005 at 10:10:08AM -0700, Mingming Cao wrote:
> On Fri, 2005-04-29 at 19:22 +0530, Suparna Bhattacharya wrote:
> > On Thu, Apr 28, 2005 at 12:14:24PM -0700, Mingming Cao wrote:
> > > Currently ext3_get_block()/ext3_new_block() only allocate one block at a
> > > time.  To allocate multiple blocks, the caller, for example, ext3 direct
> > > IO routine, has to invoke ext3_get_block() many times.  This is quite
> > > inefficient for sequential IO workload. 
> > > 
> > > The benefit of a real get_blocks() include
> > > 1) increase the possibility to get contiguous blocks, reduce possibility
> > > of  fragmentation due to interleaved allocations from other threads.
> > > (should good for non reservation case)
> > > 2) Reduces CPU cycles spent in repeated get_block() calls
> > > 3) Batch meta data update and journaling in one short
> > > 4) Could possibly speed up future get_blocks() look up by cache the last
> > > mapped blocks in inode.
> > > 
> > 
> > And here is the patch to make mpage_writepages use get_blocks() for
> > multiple block lookup/allocation. It performs a radix-tree contiguous 
> > pages lookup, and issues a get_blocks for the range together. It maintains
> > an mpageio structure to track intermediate mapping state, somewhat
> > like the DIO code.
> > 
> > It does need some more testing, especially block_size < PAGE_SIZE.
> > The JFS workaround can be dropped if the JFS get_blocks fix from
> > Dave Kleikamp is integrated.
> > 
> > Review feedback would be welcome.
> > 
> > Mingming,
> > Let me know if you have a chance to try this out with your patch.
> 
> 
> Sure, Suparna, I will try your patch soon!
> 
> In my patch,  I have modified ext3 directo io code to make use of
> ext3_get_blocks(). Tested with a simple file write with O_DIRECT, seems
> work fine! Allocating blocks for a 120k file only invokes
> ext3_get_blocks() for 4 times(perfect is 1, but before is 30 times call
> to ext3_get_block). Among the 4 calls to ext3_get_blocks, 2 because of
> reach the meta data block boundary(direct ->indirect), another 2 because
> of reach the end of the reservation window. For the later 2, we could
> avoid that by extend the reservation window before calling
> ext3_new_blocks() if the window size is less than the number of blocks
> to allocate.
> 
> But if it try to allocating blocks in the hole (with direct IO), blocks
> are allocated one by one. I am looking at it right now.

That is expected, because DIO falls back to using buffered IO for
overwriting holes. This is to avoid some tricky races between DIO
and buffered IO that could otherwise have led to exposure of
stale data.

Regards
Suparna

> 
> Thanks,
> Mingming
> 

-- 
Suparna Bhattacharya (suparna@in.ibm.com)
Linux Technology Center
IBM Software Lab, India

Re: [Ext2-devel] [RFC] Adding multiple block allocation

[Badari Pulavarty]

Suparna Bhattacharya wrote:
> On Thu, Apr 28, 2005 at 12:14:24PM -0700, Mingming Cao wrote:
> 
>>Currently ext3_get_block()/ext3_new_block() only allocate one block at a
>>time.  To allocate multiple blocks, the caller, for example, ext3 direct
>>IO routine, has to invoke ext3_get_block() many times.  This is quite
>>inefficient for sequential IO workload. 
>>
>>The benefit of a real get_blocks() include
>>1) increase the possibility to get contiguous blocks, reduce possibility
>>of  fragmentation due to interleaved allocations from other threads.
>>(should good for non reservation case)
>>2) Reduces CPU cycles spent in repeated get_block() calls
>>3) Batch meta data update and journaling in one short
>>4) Could possibly speed up future get_blocks() look up by cache the last
>>mapped blocks in inode.
>>
> 
> 
> And here is the patch to make mpage_writepages use get_blocks() for
> multiple block lookup/allocation. It performs a radix-tree contiguous 
> pages lookup, and issues a get_blocks for the range together. It maintains
> an mpageio structure to track intermediate mapping state, somewhat
> like the DIO code.
> 
> It does need some more testing, especially block_size < PAGE_SIZE.
> The JFS workaround can be dropped if the JFS get_blocks fix from
> Dave Kleikamp is integrated.
> 
> Review feedback would be welcome.
> 
> Mingming,
> Let me know if you have a chance to try this out with your patch.
> 
> Regards
> Suparna
> 

Suparna,

I touch tested your patch earlier and seems to work fine. Lets integrate
Mingming's getblocks() patches with this and see if we get any benifit
from the whole effort.

BTW,  is it the plan to remove repeated calls to getblocks() and work
with whatever getblocks() returned ? Or do you find the its better to
repeatedly do getblocks() in a loop till you satisfy all the pages
in the list (as long as blocks are contiguous) ?

Thanks,
Badari

Re: [Ext2-devel] [RFC] Adding multiple block allocation

[Mingming Cao]

On Fri, 2005-04-29 at 11:45 -0700, Badari Pulavarty wrote:
> I touch tested your patch earlier and seems to work fine. Lets integrate
> Mingming's getblocks() patches with this and see if we get any benifit
> from the whole effort.
> 

I tried Suparna's mpage_writepages_getblocks patch with my
ext3_get_blocks patch, seems to work fine,  except that still only one
block is allocated at a time. I got a little confused.... 

I did not see any delayed allocation code in your patch, I assume you
have to update ext3_prepare_write to not call ext3_get_block, so that
block allocation will be defered at ext3_writepages time. So without the
delayed allocation part, the get_blocks in mpage_writepages is doing
multiple blocks look up only, right?


Mingming

Re: [RFC] Adding multiple block allocation

[Suparna Bhattacharya]

On Fri, Apr 29, 2005 at 04:22:59PM -0700, Mingming Cao wrote:
> On Fri, 2005-04-29 at 11:45 -0700, Badari Pulavarty wrote:
> > I touch tested your patch earlier and seems to work fine. Lets integrate
> > Mingming's getblocks() patches with this and see if we get any benifit
> > from the whole effort.
> > 
> 
> I tried Suparna's mpage_writepages_getblocks patch with my
> ext3_get_blocks patch, seems to work fine,  except that still only one
> block is allocated at a time. I got a little confused.... 
> 
> I did not see any delayed allocation code in your patch, I assume you
> have to update ext3_prepare_write to not call ext3_get_block, so that
> block allocation will be defered at ext3_writepages time. So without the
> delayed allocation part, the get_blocks in mpage_writepages is doing
> multiple blocks look up only, right?

That's right - so you could try it with mmapped writes (which don't
go through a prepare write) or with Badari's patch to not call
ext3_get_block in prepare write.

Regards
Suparna
> 
> 
> Mingming
> 
> 
> 
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-- 
Suparna Bhattacharya (suparna@in.ibm.com)
Linux Technology Center
IBM Software Lab, India



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Re: [Ext2-devel] [RFC] Adding multiple block allocation

[Suparna Bhattacharya]

On Sat, Apr 30, 2005 at 09:40:43PM +0530, Suparna Bhattacharya wrote:
> On Fri, Apr 29, 2005 at 04:22:59PM -0700, Mingming Cao wrote:
> > On Fri, 2005-04-29 at 11:45 -0700, Badari Pulavarty wrote:
> > > I touch tested your patch earlier and seems to work fine. Lets integrate
> > > Mingming's getblocks() patches with this and see if we get any benifit
> > > from the whole effort.
> > > 
> > 
> > I tried Suparna's mpage_writepages_getblocks patch with my
> > ext3_get_blocks patch, seems to work fine,  except that still only one
> > block is allocated at a time. I got a little confused.... 
> > 
> > I did not see any delayed allocation code in your patch, I assume you
> > have to update ext3_prepare_write to not call ext3_get_block, so that
> > block allocation will be defered at ext3_writepages time. So without the
> > delayed allocation part, the get_blocks in mpage_writepages is doing
> > multiple blocks look up only, right?
> 
> That's right - so you could try it with mmapped writes (which don't
> go through a prepare write) or with Badari's patch to not call
> ext3_get_block in prepare write.

BTW, I hope you are running with NOBH.

Regards
Suparna

> 
> Regards
> Suparna
> > 
> > 
> > Mingming
> > 
> > 
> > 
> > -------------------------------------------------------
> > This SF.Net email is sponsored by: NEC IT Guy Games.
> > Get your fingers limbered up and give it your best shot. 4 great events, 4
> > opportunities to win big! Highest score wins.NEC IT Guy Games. Play to
> > win an NEC 61 plasma display. Visit http://www.necitguy.com/?r=20
> > _______________________________________________
> > Ext2-devel mailing list
> > Ext2-devel@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/ext2-devel
> 
> -- 
> Suparna Bhattacharya (suparna@in.ibm.com)
> Linux Technology Center
> IBM Software Lab, India
> 
> 
> 
> -------------------------------------------------------
> This SF.Net email is sponsored by: NEC IT Guy Games.
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> opportunities to win big! Highest score wins.NEC IT Guy Games. Play to
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> _______________________________________________
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> Ext2-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/ext2-devel

-- 
Suparna Bhattacharya (suparna@in.ibm.com)
Linux Technology Center
IBM Software Lab, India

Re: [Ext2-devel] [RFC] Adding multiple block allocation

[Mingming Cao]

On Sat, 2005-04-30 at 22:41 +0530, Suparna Bhattacharya wrote:
> On Sat, Apr 30, 2005 at 09:40:43PM +0530, Suparna Bhattacharya wrote:
> > On Fri, Apr 29, 2005 at 04:22:59PM -0700, Mingming Cao wrote:
> > > On Fri, 2005-04-29 at 11:45 -0700, Badari Pulavarty wrote:
> > > > I touch tested your patch earlier and seems to work fine. Lets integrate
> > > > Mingming's getblocks() patches with this and see if we get any benifit
> > > > from the whole effort.
> > > > 
> > > 
> > > I tried Suparna's mpage_writepages_getblocks patch with my
> > > ext3_get_blocks patch, seems to work fine,  except that still only one
> > > block is allocated at a time. I got a little confused.... 
> > > 
> > > I did not see any delayed allocation code in your patch, I assume you
> > > have to update ext3_prepare_write to not call ext3_get_block, so that
> > > block allocation will be defered at ext3_writepages time. So without the
> > > delayed allocation part, the get_blocks in mpage_writepages is doing
> > > multiple blocks look up only, right?
> > 
> > That's right - so you could try it with mmapped writes (which don't
> > go through a prepare write) or with Badari's patch to not call
> > ext3_get_block in prepare write.
> 
> BTW, I hope you are running with NOBH.

No, it was not run with NOBH. Why we need to turn on nobh here?

There are some issue running fsx tests with both patches, w/o direct io
option. I will spend more time on this next week.

thanks,
Mingming

Re: [Ext2-devel] [RFC] Adding multiple block allocation

[Suparna Bhattacharya]

On Sat, Apr 30, 2005 at 11:07:53AM -0700, Mingming Cao wrote:
> On Sat, 2005-04-30 at 22:41 +0530, Suparna Bhattacharya wrote:
> > On Sat, Apr 30, 2005 at 09:40:43PM +0530, Suparna Bhattacharya wrote:
> > > On Fri, Apr 29, 2005 at 04:22:59PM -0700, Mingming Cao wrote:
> > > > On Fri, 2005-04-29 at 11:45 -0700, Badari Pulavarty wrote:
> > > > > I touch tested your patch earlier and seems to work fine. Lets integrate
> > > > > Mingming's getblocks() patches with this and see if we get any benifit
> > > > > from the whole effort.
> > > > > 
> > > > 
> > > > I tried Suparna's mpage_writepages_getblocks patch with my
> > > > ext3_get_blocks patch, seems to work fine,  except that still only one
> > > > block is allocated at a time. I got a little confused.... 
> > > > 
> > > > I did not see any delayed allocation code in your patch, I assume you
> > > > have to update ext3_prepare_write to not call ext3_get_block, so that
> > > > block allocation will be defered at ext3_writepages time. So without the
> > > > delayed allocation part, the get_blocks in mpage_writepages is doing
> > > > multiple blocks look up only, right?
> > > 
> > > That's right - so you could try it with mmapped writes (which don't
> > > go through a prepare write) or with Badari's patch to not call
> > > ext3_get_block in prepare write.
> > 
> > BTW, I hope you are running with NOBH.
> 
> No, it was not run with NOBH. Why we need to turn on nobh here?

If the page has buffers, then get_blocks won't be invoked -- it either
finds all the buffers in a page to be mapped contiguous, in which case
it can directly issue the IO or enters the confused case where it goes
through block_write_full_page.

> 
> There are some issue running fsx tests with both patches, w/o direct io
> option. I will spend more time on this next week.

OK, I can take a look at the fsx logs, just in case it is similar to
something I've seen before.

Regards
Suparna

-- 
Suparna Bhattacharya (suparna@in.ibm.com)
Linux Technology Center
IBM Software Lab, India

Re: [Ext2-devel] [RFC] Adding multiple block allocation

[Suparna Bhattacharya]

On Fri, Apr 29, 2005 at 11:45:21AM -0700, Badari Pulavarty wrote:
> Suparna Bhattacharya wrote:
> >On Thu, Apr 28, 2005 at 12:14:24PM -0700, Mingming Cao wrote:
> >
> >>Currently ext3_get_block()/ext3_new_block() only allocate one block at a
> >>time.  To allocate multiple blocks, the caller, for example, ext3 direct
> >>IO routine, has to invoke ext3_get_block() many times.  This is quite
> >>inefficient for sequential IO workload. 
> >>
> >>The benefit of a real get_blocks() include
> >>1) increase the possibility to get contiguous blocks, reduce possibility
> >>of  fragmentation due to interleaved allocations from other threads.
> >>(should good for non reservation case)
> >>2) Reduces CPU cycles spent in repeated get_block() calls
> >>3) Batch meta data update and journaling in one short
> >>4) Could possibly speed up future get_blocks() look up by cache the last
> >>mapped blocks in inode.
> >>
> >
> >
> >And here is the patch to make mpage_writepages use get_blocks() for
> >multiple block lookup/allocation. It performs a radix-tree contiguous 
> >pages lookup, and issues a get_blocks for the range together. It maintains
> >an mpageio structure to track intermediate mapping state, somewhat
> >like the DIO code.
> >
> >It does need some more testing, especially block_size < PAGE_SIZE.
> >The JFS workaround can be dropped if the JFS get_blocks fix from
> >Dave Kleikamp is integrated.
> >
> >Review feedback would be welcome.
> >
> >Mingming,
> >Let me know if you have a chance to try this out with your patch.
> >
> >Regards
> >Suparna
> >
> 
> Suparna,
> 
> I touch tested your patch earlier and seems to work fine. Lets integrate
> Mingming's getblocks() patches with this and see if we get any benifit
> from the whole effort.
> 
> BTW,  is it the plan to remove repeated calls to getblocks() and work
> with whatever getblocks() returned ? Or do you find the its better to
> repeatedly do getblocks() in a loop till you satisfy all the pages
> in the list (as long as blocks are contiguous) ?

The patch only loops through repeated get_blocks upto PAGE_SIZE, just
like the earlier mpage_writepage code - in this case if blocks aren't
contiguous at least upto PAGE_SIZE, it would fall back to confused case
(since it means multiple ios for the same page) just as before. 
What is new now is just the numblocks specified to get_blocks, so in
case it gets more contiguous blocks it can remember that mapping and 
avoid get_blocks calls for subsequent pages.

Does that clarify ?

Regards
Suparna

-- 
Suparna Bhattacharya (suparna@in.ibm.com)
Linux Technology Center
IBM Software Lab, India

Re: [RFC] Adding multiple block allocation

[Mingming Cao]

On Fri, 2005-04-29 at 19:22 +0530, Suparna Bhattacharya wrote:
> On Thu, Apr 28, 2005 at 12:14:24PM -0700, Mingming Cao wrote:
> > Currently ext3_get_block()/ext3_new_block() only allocate one block at a
> > time.  To allocate multiple blocks, the caller, for example, ext3 direct
> > IO routine, has to invoke ext3_get_block() many times.  This is quite
> > inefficient for sequential IO workload. 
> > 
> > The benefit of a real get_blocks() include
> > 1) increase the possibility to get contiguous blocks, reduce possibility
> > of  fragmentation due to interleaved allocations from other threads.
> > (should good for non reservation case)
> > 2) Reduces CPU cycles spent in repeated get_block() calls
> > 3) Batch meta data update and journaling in one short
> > 4) Could possibly speed up future get_blocks() look up by cache the last
> > mapped blocks in inode.
> > 
> 
> And here is the patch to make mpage_writepages use get_blocks() for
> multiple block lookup/allocation. It performs a radix-tree contiguous 
> pages lookup, and issues a get_blocks for the range together. It maintains
> an mpageio structure to track intermediate mapping state, somewhat
> like the DIO code.
> 
> It does need some more testing, especially block_size < PAGE_SIZE.
> The JFS workaround can be dropped if the JFS get_blocks fix from
> Dave Kleikamp is integrated.
> 
> Review feedback would be welcome.
> 
> Mingming,
> Let me know if you have a chance to try this out with your patch.
> 
> Regards
> Suparna
> 
> -- 
> Suparna Bhattacharya (suparna@in.ibm.com)
> Linux Technology Center
> IBM Software Lab, India
> 
> 
> diff -urp -X dontdiff linux-2.6.12-rc3/fs/buffer.c linux-2.6.12-rc3-getblocks/fs/buffer.c
> --- linux-2.6.12-rc3/fs/buffer.c	2005-04-21 05:33:15.000000000 +0530
> +++ linux-2.6.12-rc3-getblocks/fs/buffer.c	2005-04-22 15:08:33.000000000 +0530
> @@ -2514,53 +2514,10 @@ EXPORT_SYMBOL(nobh_commit_write);
>   * that it tries to operate without attaching bufferheads to
>   * the page.
>   */
> -int nobh_writepage(struct page *page, get_block_t *get_block,
> -			struct writeback_control *wbc)
> +int nobh_writepage(struct page *page, get_blocks_t *get_blocks,
> +		struct writeback_control *wbc, writepage_t bh_writepage_fn)
>  {
> -	struct inode * const inode = page->mapping->host;
> -	loff_t i_size = i_size_read(inode);
> -	const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
> -	unsigned offset;
> -	void *kaddr;
> -	int ret;
> -
> -	/* Is the page fully inside i_size? */
> -	if (page->index < end_index)
> -		goto out;
> -
> -	/* Is the page fully outside i_size? (truncate in progress) */
> -	offset = i_size & (PAGE_CACHE_SIZE-1);
> -	if (page->index >= end_index+1 || !offset) {
> -		/*
> -		 * The page may have dirty, unmapped buffers.  For example,
> -		 * they may have been added in ext3_writepage().  Make them
> -		 * freeable here, so the page does not leak.
> -		 */
> -#if 0
> -		/* Not really sure about this  - do we need this ? */
> -		if (page->mapping->a_ops->invalidatepage)
> -			page->mapping->a_ops->invalidatepage(page, offset);
> -#endif
> -		unlock_page(page);
> -		return 0; /* don't care */
> -	}
> -
> -	/*
> -	 * The page straddles i_size.  It must be zeroed out on each and every
> -	 * writepage invocation because it may be mmapped.  "A file is mapped
> -	 * in multiples of the page size.  For a file that is not a multiple of
> -	 * the  page size, the remaining memory is zeroed when mapped, and
> -	 * writes to that region are not written out to the file."
> -	 */
> -	kaddr = kmap_atomic(page, KM_USER0);
> -	memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset);
> -	flush_dcache_page(page);
> -	kunmap_atomic(kaddr, KM_USER0);
> -out:
> -	ret = mpage_writepage(page, get_block, wbc);
> -	if (ret == -EAGAIN)
> -		ret = __block_write_full_page(inode, page, get_block, wbc);
> -	return ret;
> +	return mpage_writepage(page, get_blocks, wbc, bh_writepage_fn);
>  }
>  EXPORT_SYMBOL(nobh_writepage);
>  
> diff -urp -X dontdiff linux-2.6.12-rc3/fs/ext2/inode.c linux-2.6.12-rc3-getblocks/fs/ext2/inode.c
> --- linux-2.6.12-rc3/fs/ext2/inode.c	2005-04-21 05:33:15.000000000 +0530
> +++ linux-2.6.12-rc3-getblocks/fs/ext2/inode.c	2005-04-22 16:30:42.000000000 +0530
> @@ -639,12 +639,6 @@ ext2_nobh_prepare_write(struct file *fil
>  	return nobh_prepare_write(page,from,to,ext2_get_block);
>  }
>  
> -static int ext2_nobh_writepage(struct page *page,
> -			struct writeback_control *wbc)
> -{
> -	return nobh_writepage(page, ext2_get_block, wbc);
> -}
> -
>  static sector_t ext2_bmap(struct address_space *mapping, sector_t block)
>  {
>  	return generic_block_bmap(mapping,block,ext2_get_block);
> @@ -662,6 +656,12 @@ ext2_get_blocks(struct inode *inode, sec
>  	return ret;
>  }
>  
> +static int ext2_nobh_writepage(struct page *page,
> +			struct writeback_control *wbc)
> +{
> +	return nobh_writepage(page, ext2_get_blocks, wbc, ext2_writepage);
> +}
> +
>  static ssize_t
>  ext2_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
>  			loff_t offset, unsigned long nr_segs)
> @@ -676,7 +676,8 @@ ext2_direct_IO(int rw, struct kiocb *ioc
>  static int
>  ext2_writepages(struct address_space *mapping, struct writeback_control *wbc)
>  {
> -	return mpage_writepages(mapping, wbc, ext2_get_block);
> +        return __mpage_writepages(mapping, wbc, ext2_get_blocks,
> +					ext2_writepage);
>  }
>  
>  struct address_space_operations ext2_aops = {
> diff -urp -X dontdiff linux-2.6.12-rc3/fs/ext3/inode.c linux-2.6.12-rc3-getblocks/fs/ext3/inode.c
> --- linux-2.6.12-rc3/fs/ext3/inode.c	2005-04-21 05:33:15.000000000 +0530
> +++ linux-2.6.12-rc3-getblocks/fs/ext3/inode.c	2005-04-22 15:08:33.000000000 +0530
> @@ -866,10 +866,10 @@ get_block:
>  	return ret;
>  }
>  
> -static int ext3_writepages_get_block(struct inode *inode, sector_t iblock,
> -			struct buffer_head *bh, int create)
> +static int ext3_writepages_get_blocks(struct inode *inode, sector_t iblock,
> +		unsigned long max_blocks, struct buffer_head *bh, int create)
>  {
> -	return ext3_direct_io_get_blocks(inode, iblock, 1, bh, create);
> +	return ext3_direct_io_get_blocks(inode, iblock, max_blocks, bh, create);
>  }
>  
>  /*
> @@ -1369,11 +1369,11 @@ ext3_writeback_writepages(struct address
>  		return ret;
>  	}
>  
> -        ret = __mpage_writepages(mapping, wbc, ext3_writepages_get_block,
> +        ret = __mpage_writepages(mapping, wbc, ext3_writepages_get_blocks,
>  					ext3_writeback_writepage_helper);
>  
>  	/*
> -	 * Need to reaquire the handle since ext3_writepages_get_block()
> +	 * Need to reaquire the handle since ext3_writepages_get_blocks()
>  	 * can restart the handle
>  	 */
>  	handle = journal_current_handle();
> @@ -1402,7 +1402,8 @@ static int ext3_writeback_writepage(stru
>  	}
>  
>  	if (test_opt(inode->i_sb, NOBH))
> -		ret = nobh_writepage(page, ext3_get_block, wbc);
> +		ret = nobh_writepage(page, ext3_writepages_get_blocks, wbc,
> +			ext3_writeback_writepage_helper);
>  	else
>  		ret = block_write_full_page(page, ext3_get_block, wbc);
>  
> diff -urp -X dontdiff linux-2.6.12-rc3/fs/ext3/super.c linux-2.6.12-rc3-getblocks/fs/ext3/super.c
> --- linux-2.6.12-rc3/fs/ext3/super.c	2005-04-21 05:33:15.000000000 +0530
> +++ linux-2.6.12-rc3-getblocks/fs/ext3/super.c	2005-04-22 15:08:33.000000000 +0530
> @@ -1321,6 +1321,7 @@ static int ext3_fill_super (struct super
>  	sbi->s_resgid = le16_to_cpu(es->s_def_resgid);
>  
>  	set_opt(sbi->s_mount_opt, RESERVATION);
> +	set_opt(sbi->s_mount_opt, NOBH); /* temp: set nobh default */
>  
>  	if (!parse_options ((char *) data, sb, &journal_inum, NULL, 0))
>  		goto failed_mount;
> @@ -1567,6 +1568,7 @@ static int ext3_fill_super (struct super
>  			printk(KERN_ERR "EXT3-fs: Journal does not support "
>  			       "requested data journaling mode\n");
>  			goto failed_mount3;
> +		set_opt(sbi->s_mount_opt, NOBH); /* temp: set nobh default */
>  		}
>  	default:
>  		break;
> @@ -1584,6 +1586,7 @@ static int ext3_fill_super (struct super
>  				"its supported only with writeback mode\n");
>  			clear_opt(sbi->s_mount_opt, NOBH);
>  		}
> +		printk("NOBH option set\n");
>  	}
>  	/*
>  	 * The journal_load will have done any necessary log recovery,
> diff -urp -X dontdiff linux-2.6.12-rc3/fs/hfs/inode.c linux-2.6.12-rc3-getblocks/fs/hfs/inode.c
> --- linux-2.6.12-rc3/fs/hfs/inode.c	2005-04-21 05:33:15.000000000 +0530
> +++ linux-2.6.12-rc3-getblocks/fs/hfs/inode.c	2005-04-22 15:08:33.000000000 +0530
> @@ -124,7 +124,7 @@ static ssize_t hfs_direct_IO(int rw, str
>  static int hfs_writepages(struct address_space *mapping,
>  			  struct writeback_control *wbc)
>  {
> -	return mpage_writepages(mapping, wbc, hfs_get_block);
> +	return mpage_writepages(mapping, wbc, hfs_get_blocks);
>  }
>  
>  struct address_space_operations hfs_btree_aops = {
> diff -urp -X dontdiff linux-2.6.12-rc3/fs/hfsplus/inode.c linux-2.6.12-rc3-getblocks/fs/hfsplus/inode.c
> --- linux-2.6.12-rc3/fs/hfsplus/inode.c	2005-04-21 05:33:15.000000000 +0530
> +++ linux-2.6.12-rc3-getblocks/fs/hfsplus/inode.c	2005-04-22 15:08:33.000000000 +0530
> @@ -121,7 +121,7 @@ static ssize_t hfsplus_direct_IO(int rw,
>  static int hfsplus_writepages(struct address_space *mapping,
>  			      struct writeback_control *wbc)
>  {
> -	return mpage_writepages(mapping, wbc, hfsplus_get_block);
> +	return mpage_writepages(mapping, wbc, hfsplus_get_blocks);
>  }
>  
>  struct address_space_operations hfsplus_btree_aops = {
> diff -urp -X dontdiff linux-2.6.12-rc3/fs/jfs/inode.c linux-2.6.12-rc3-getblocks/fs/jfs/inode.c
> --- linux-2.6.12-rc3/fs/jfs/inode.c	2005-04-21 05:33:15.000000000 +0530
> +++ linux-2.6.12-rc3-getblocks/fs/jfs/inode.c	2005-04-22 16:27:19.000000000 +0530
> @@ -267,21 +267,41 @@ jfs_get_blocks(struct inode *ip, sector_
>  	return rc;
>  }
>  
> +static int
> +jfs_mpage_get_blocks(struct inode *ip, sector_t lblock, unsigned long
> +			max_blocks, struct buffer_head *bh_result, int create)
> +{
> +	/* 
> +	 * fixme: temporary workaround: return one block at a time until
> +	 * we figure out why we see exposures with truncate on 
> +	 * allocating multiple blocks in one shot.
> +	 */
> +	return jfs_get_blocks(ip, lblock, 1, bh_result, create);
> +}
> +
>  static int jfs_get_block(struct inode *ip, sector_t lblock,
>  			 struct buffer_head *bh_result, int create)
>  {
>  	return jfs_get_blocks(ip, lblock, 1, bh_result, create);
>  }
>  
> +static int jfs_bh_writepage(struct page *page,
> +				struct writeback_control *wbc)
> +{
> +	return block_write_full_page(page, jfs_get_block, wbc);
> +}
> +
> +
>  static int jfs_writepage(struct page *page, struct writeback_control *wbc)
>  {
> -	return nobh_writepage(page, jfs_get_block, wbc);
> +	return nobh_writepage(page, jfs_mpage_get_blocks, wbc, jfs_bh_writepage);
>  }
>  
>  static int jfs_writepages(struct address_space *mapping,
>  			struct writeback_control *wbc)
>  {
> -	return mpage_writepages(mapping, wbc, jfs_get_block);
> +        return __mpage_writepages(mapping, wbc, jfs_mpage_get_blocks,
> +					jfs_bh_writepage);
>  }
>  
>  static int jfs_readpage(struct file *file, struct page *page)
> diff -urp -X dontdiff linux-2.6.12-rc3/fs/mpage.c linux-2.6.12-rc3-getblocks/fs/mpage.c
> --- linux-2.6.12-rc3/fs/mpage.c	2005-04-21 05:33:15.000000000 +0530
> +++ linux-2.6.12-rc3-getblocks/fs/mpage.c	2005-04-22 16:19:14.000000000 +0530
> @@ -370,6 +370,67 @@ int mpage_readpage(struct page *page, ge
>  }
>  EXPORT_SYMBOL(mpage_readpage);
>  
> +struct mpageio {
> +	struct bio *bio;
> +	struct buffer_head map_bh;
> +	unsigned long block_in_file;
> +	unsigned long final_block_in_request;
> +	sector_t long block_in_bio;
> +	int boundary;
> +	sector_t boundary_block;
> +	struct block_device *boundary_bdev;
> +};
> +
> +/*
> + * Maps as many contiguous disk blocks as it can within the range of
> + * the request, and returns the total number of contiguous mapped
> + * blocks in the mpageio.
> + */
> +static unsigned long mpage_get_more_blocks(struct mpageio *mio,
> +	struct inode *inode, get_blocks_t get_blocks)
> +{
> +	struct buffer_head map_bh = {.b_state = 0};
> +	unsigned long mio_nblocks = mio->map_bh.b_size >> inode->i_blkbits;
> +	unsigned long first_unmapped = mio->block_in_file + mio_nblocks;
> +	unsigned long next_contig_block = mio->map_bh.b_blocknr + mio_nblocks;
> +
> +	while ((first_unmapped < mio->final_block_in_request) &&
> +		(mio->map_bh.b_size < PAGE_SIZE)) {
> +
> +		if (get_blocks(inode, first_unmapped,
> +			mio->final_block_in_request - first_unmapped,
> +			&map_bh, 1))
> +			break;
> +		if (mio_nblocks && ((map_bh.b_blocknr != next_contig_block) ||
> +			map_bh.b_bdev != mio->map_bh.b_bdev))
> +			break;
> +			
> +		if (buffer_new(&map_bh)) {
> +			int i = 0;
> +			for (; i < map_bh.b_size >> inode->i_blkbits; i++)
> +				unmap_underlying_metadata(map_bh.b_bdev,
> +					map_bh.b_blocknr + i);
> +		}
> +		
> +		if (buffer_boundary(&map_bh)) {
> +			mio->boundary = 1;
> +			mio->boundary_block = map_bh.b_blocknr;
> +			mio->boundary_bdev = map_bh.b_bdev;
> +		}
> +		if (mio_nblocks == 0) {
> +			mio->map_bh.b_bdev = map_bh.b_bdev;
> +			mio->map_bh.b_blocknr = map_bh.b_blocknr;
> +		}
> +
> +		mio_nblocks += map_bh.b_size >> inode->i_blkbits;
> +		first_unmapped = mio->block_in_file + mio_nblocks;
> +		next_contig_block = mio->map_bh.b_blocknr + mio_nblocks;
> +		mio->map_bh.b_size += map_bh.b_size;
> +	}
> +
> +	return mio_nblocks;
> +}
> +
>  /*
>   * Writing is not so simple.
>   *
> @@ -386,9 +447,9 @@ EXPORT_SYMBOL(mpage_readpage);
>   * written, so it can intelligently allocate a suitably-sized BIO.  For now,
>   * just allocate full-size (16-page) BIOs.
>   */
> -static struct bio *
> -__mpage_writepage(struct bio *bio, struct page *page, get_block_t get_block,
> -	sector_t *last_block_in_bio, int *ret, struct writeback_control *wbc,
> +static int
> +__mpage_writepage(struct mpageio *mio, struct page *page,
> +	get_blocks_t get_blocks, struct writeback_control *wbc,
>  	writepage_t writepage_fn)
>  {
>  	struct address_space *mapping = page->mapping;
> @@ -396,9 +457,8 @@ __mpage_writepage(struct bio *bio, struc
>  	const unsigned blkbits = inode->i_blkbits;
>  	unsigned long end_index;
>  	const unsigned blocks_per_page = PAGE_CACHE_SIZE >> blkbits;
> -	sector_t last_block;
> +	sector_t last_block, blocks_to_skip;
>  	sector_t block_in_file;
> -	sector_t blocks[MAX_BUF_PER_PAGE];
>  	unsigned page_block;
>  	unsigned first_unmapped = blocks_per_page;
>  	struct block_device *bdev = NULL;
> @@ -406,8 +466,10 @@ __mpage_writepage(struct bio *bio, struc
>  	sector_t boundary_block = 0;
>  	struct block_device *boundary_bdev = NULL;
>  	int length;
> -	struct buffer_head map_bh;
>  	loff_t i_size = i_size_read(inode);
> +	struct buffer_head *map_bh = &mio->map_bh;
> +	struct bio *bio = mio->bio;
> +	int ret = 0;
>  
>  	if (page_has_buffers(page)) {
>  		struct buffer_head *head = page_buffers(page);
> @@ -435,10 +497,13 @@ __mpage_writepage(struct bio *bio, struc
>  			if (!buffer_dirty(bh) || !buffer_uptodate(bh))
>  				goto confused;
>  			if (page_block) {
> -				if (bh->b_blocknr != blocks[page_block-1] + 1)
> +				if (bh->b_blocknr != map_bh->b_blocknr 
> +					+ page_block)
>  					goto confused;
> +			} else {
> +				map_bh->b_blocknr = bh->b_blocknr;
> +				map_bh->b_size = PAGE_SIZE;
>  			}
> -			blocks[page_block++] = bh->b_blocknr;
>  			boundary = buffer_boundary(bh);
>  			if (boundary) {
>  				boundary_block = bh->b_blocknr;
> @@ -465,33 +530,30 @@ __mpage_writepage(struct bio *bio, struc
>  	BUG_ON(!PageUptodate(page));
>  	block_in_file = page->index << (PAGE_CACHE_SHIFT - blkbits);
>  	last_block = (i_size - 1) >> blkbits;
> -	map_bh.b_page = page;
> -	for (page_block = 0; page_block < blocks_per_page; ) {
> -
> -		map_bh.b_state = 0;
> -		if (get_block(inode, block_in_file, &map_bh, 1))
> -			goto confused;
> -		if (buffer_new(&map_bh))
> -			unmap_underlying_metadata(map_bh.b_bdev,
> -						map_bh.b_blocknr);
> -		if (buffer_boundary(&map_bh)) {
> -			boundary_block = map_bh.b_blocknr;
> -			boundary_bdev = map_bh.b_bdev;
> -		}
> -		if (page_block) {
> -			if (map_bh.b_blocknr != blocks[page_block-1] + 1)
> -				goto confused;
> -		}
> -		blocks[page_block++] = map_bh.b_blocknr;
> -		boundary = buffer_boundary(&map_bh);
> -		bdev = map_bh.b_bdev;
> -		if (block_in_file == last_block)
> -			break;
> -		block_in_file++;
> +	blocks_to_skip = block_in_file - mio->block_in_file;
> +	mio->block_in_file = block_in_file;
> +	if (blocks_to_skip < (map_bh->b_size >> blkbits)) {
> +		map_bh->b_blocknr += blocks_to_skip;
> +		map_bh->b_size -= blocks_to_skip << blkbits;
> +	} else {
> +		map_bh->b_state = 0;
> +		map_bh->b_size = 0;
> +		if (mio->final_block_in_request > last_block)
> +			mio->final_block_in_request = last_block;
> +		mpage_get_more_blocks(mio, inode, get_blocks);
>  	}
> -	BUG_ON(page_block == 0);
> +	if (map_bh->b_size < PAGE_SIZE)
> +		goto confused;
>  
> -	first_unmapped = page_block;
> +	if (mio->boundary && (mio->boundary_block < map_bh->b_blocknr 
> +		+ blocks_per_page)) {
> +		boundary = 1;
> +		boundary_block = mio->boundary_block;
> +		boundary_bdev = mio->boundary_bdev;
> +	}
> +		
> +	bdev = map_bh->b_bdev;
> +	first_unmapped = blocks_per_page;
>  
>  page_is_mapped:
>  	end_index = i_size >> PAGE_CACHE_SHIFT;
> @@ -518,12 +580,16 @@ page_is_mapped:
>  	/*
>  	 * This page will go to BIO.  Do we need to send this BIO off first?
>  	 */
> -	if (bio && *last_block_in_bio != blocks[0] - 1)
> +	if (bio && mio->block_in_bio != map_bh->b_blocknr - 1)
>  		bio = mpage_bio_submit(WRITE, bio);
>  
>  alloc_new:
>  	if (bio == NULL) {
> -		bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9),
> +		/* 
> +		 * Fixme: bio size can be limited to final_block - block, or
> +		 * even mio->map_bh.b_size
> +		 */
> +		bio = mpage_alloc(bdev, map_bh->b_blocknr << (blkbits - 9),
>  				bio_get_nr_vecs(bdev), GFP_NOFS|__GFP_HIGH);
>  		if (bio == NULL)
>  			goto confused;
> @@ -539,6 +605,9 @@ alloc_new:
>  		bio = mpage_bio_submit(WRITE, bio);
>  		goto alloc_new;
>  	}
> +	map_bh->b_blocknr += blocks_per_page;
> +	map_bh->b_size -= PAGE_SIZE;
> +	mio->block_in_file += blocks_per_page;
>  
>  	/*
>  	 * OK, we have our BIO, so we can now mark the buffers clean.  Make
> @@ -575,7 +644,8 @@ alloc_new:
>  					boundary_block, 1 << blkbits);
>  		}
>  	} else {
> -		*last_block_in_bio = blocks[blocks_per_page - 1];
> +		/* we can pack more pages into the bio, don't submit yet */
> +		mio->block_in_bio = map_bh->b_blocknr - 1;
>  	}
>  	goto out;
>  
> @@ -584,22 +654,23 @@ confused:
>  		bio = mpage_bio_submit(WRITE, bio);
>  
>  	if (writepage_fn) {
> -		*ret = (*writepage_fn)(page, wbc);
> +		ret = (*writepage_fn)(page, wbc);
>  	} else {
> -		*ret = -EAGAIN;
> +		ret = -EAGAIN;
>  		goto out;
>  	}
>  	/*
>  	 * The caller has a ref on the inode, so *mapping is stable
>  	 */
> -	if (*ret) {
> -		if (*ret == -ENOSPC)
> +	if (ret) {
> +		if (ret == -ENOSPC)
>  			set_bit(AS_ENOSPC, &mapping->flags);
>  		else
>  			set_bit(AS_EIO, &mapping->flags);
>  	}
>  out:
> -	return bio;
> +	mio->bio = bio;
> +	return ret;
>  }
>  
>  /**
> @@ -625,20 +696,21 @@ out:
>   */
>  int
>  mpage_writepages(struct address_space *mapping,
> -		struct writeback_control *wbc, get_block_t get_block)
> +		struct writeback_control *wbc, get_blocks_t get_blocks)
>  {
> -	return __mpage_writepages(mapping, wbc, get_block,
> +	return __mpage_writepages(mapping, wbc, get_blocks,
>  		mapping->a_ops->writepage);
>  }
>  
>  int
>  __mpage_writepages(struct address_space *mapping,
> -		struct writeback_control *wbc, get_block_t get_block,
> +		struct writeback_control *wbc, get_blocks_t get_blocks,
>  		writepage_t writepage_fn)
>  {
>  	struct backing_dev_info *bdi = mapping->backing_dev_info;
> +	struct inode *inode = mapping->host;
> +	const unsigned blkbits = inode->i_blkbits;
>  	struct bio *bio = NULL;
> -	sector_t last_block_in_bio = 0;
>  	int ret = 0;
>  	int done = 0;
>  	int (*writepage)(struct page *page, struct writeback_control *wbc);
> @@ -648,6 +720,9 @@ __mpage_writepages(struct address_space 
>  	pgoff_t end = -1;		/* Inclusive */
>  	int scanned = 0;
>  	int is_range = 0;
> +	struct mpageio mio = {
> +		.bio = NULL
> +	};
>  
>  	if (wbc->nonblocking && bdi_write_congested(bdi)) {
>  		wbc->encountered_congestion = 1;
> @@ -655,7 +730,7 @@ __mpage_writepages(struct address_space 
>  	}
>  
>  	writepage = NULL;
> -	if (get_block == NULL)
> +	if (get_blocks == NULL)
>  		writepage = mapping->a_ops->writepage;
>  
>  	pagevec_init(&pvec, 0);
> @@ -672,12 +747,15 @@ __mpage_writepages(struct address_space 
>  		scanned = 1;
>  	}
>  retry:
> +	down_read(&inode->i_alloc_sem);
>  	while (!done && (index <= end) &&
> -			(nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
> -			PAGECACHE_TAG_DIRTY,
> +			(nr_pages = pagevec_contig_lookup_tag(&pvec, mapping,
> +			&index, PAGECACHE_TAG_DIRTY,
>  			min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1))) {
>  		unsigned i;
>  
> +		mio.final_block_in_request = min(index, end) <<
> +			(PAGE_CACHE_SHIFT - blkbits);
>  		scanned = 1;
>  		for (i = 0; i < nr_pages; i++) {
>  			struct page *page = pvec.pages[i];
> @@ -702,7 +780,7 @@ retry:
>  				unlock_page(page);
>  				continue;
>  			}
> -
> +			
>  			if (wbc->sync_mode != WB_SYNC_NONE)
>  				wait_on_page_writeback(page);
>  
> @@ -723,9 +801,9 @@ retry:
>  							&mapping->flags);
>  				}
>  			} else {
> -				bio = __mpage_writepage(bio, page, get_block,
> -						&last_block_in_bio, &ret, wbc,
> -						writepage_fn);
> +				ret = __mpage_writepage(&mio, page, get_blocks,
> +						wbc, writepage_fn);
> +				bio = mio.bio;
>  			}
>  			if (ret || (--(wbc->nr_to_write) <= 0))
>  				done = 1;
> @@ -737,6 +815,9 @@ retry:
>  		pagevec_release(&pvec);
>  		cond_resched();
>  	}
> +	
> +	up_read(&inode->i_alloc_sem);
> +
>  	if (!scanned && !done) {
>  		/*
>  		 * We hit the last page and there is more work to be done: wrap
> @@ -755,17 +836,23 @@ retry:
>  EXPORT_SYMBOL(mpage_writepages);
>  EXPORT_SYMBOL(__mpage_writepages);
>  
> -int mpage_writepage(struct page *page, get_block_t get_block,
> -	struct writeback_control *wbc)
> +int mpage_writepage(struct page *page, get_blocks_t get_blocks,
> +		struct writeback_control *wbc, writepage_t writepage_fn)
>  {
>  	int ret = 0;
> -	struct bio *bio;
> -	sector_t last_block_in_bio = 0;
> -
> -	bio = __mpage_writepage(NULL, page, get_block,
> -			&last_block_in_bio, &ret, wbc, NULL);
> -	if (bio)
> -		mpage_bio_submit(WRITE, bio);
> +	struct address_space *mapping = page->mapping;
> +	struct inode *inode = mapping->host;
> +	const unsigned blkbits = inode->i_blkbits;
> +	struct mpageio mio = {
> +		.final_block_in_request = (page->index + 1) << (PAGE_CACHE_SHIFT
> +			- blkbits)
> +	};
> +
> +	dump_stack();
> +	ret = __mpage_writepage(&mio, page, get_blocks,
> +			wbc, writepage_fn);
> +	if (mio.bio)
> +		mpage_bio_submit(WRITE, mio.bio);
>  
>  	return ret;
>  }
> diff -urp -X dontdiff linux-2.6.12-rc3/include/linux/buffer_head.h linux-2.6.12-rc3-getblocks/include/linux/buffer_head.h
> --- linux-2.6.12-rc3/include/linux/buffer_head.h	2005-04-21 05:33:16.000000000 +0530
> +++ linux-2.6.12-rc3-getblocks/include/linux/buffer_head.h	2005-04-22 15:08:33.000000000 +0530
> @@ -203,8 +203,8 @@ int file_fsync(struct file *, struct den
>  int nobh_prepare_write(struct page*, unsigned, unsigned, get_block_t*);
>  int nobh_commit_write(struct file *, struct page *, unsigned, unsigned);
>  int nobh_truncate_page(struct address_space *, loff_t);
> -int nobh_writepage(struct page *page, get_block_t *get_block,
> -                        struct writeback_control *wbc);
> +int nobh_writepage(struct page *page, get_blocks_t *get_blocks,
> +	struct writeback_control *wbc, writepage_t bh_writepage);
>  
> 
>  /*
> diff -urp -X dontdiff linux-2.6.12-rc3/include/linux/fs.h linux-2.6.12-rc3-getblocks/include/linux/fs.h
> --- linux-2.6.12-rc3/include/linux/fs.h	2005-04-21 05:33:16.000000000 +0530
> +++ linux-2.6.12-rc3-getblocks/include/linux/fs.h	2005-04-22 15:08:33.000000000 +0530
> @@ -304,6 +304,8 @@ struct address_space;
>  struct writeback_control;
>  struct kiocb;
>  
> +typedef int (writepage_t)(struct page *page, struct writeback_control *wbc);
> +
>  struct address_space_operations {
>  	int (*writepage)(struct page *page, struct writeback_control *wbc);
>  	int (*readpage)(struct file *, struct page *);
> diff -urp -X dontdiff linux-2.6.12-rc3/include/linux/mpage.h linux-2.6.12-rc3-getblocks/include/linux/mpage.h
> --- linux-2.6.12-rc3/include/linux/mpage.h	2005-04-21 05:33:16.000000000 +0530
> +++ linux-2.6.12-rc3-getblocks/include/linux/mpage.h	2005-04-22 15:08:33.000000000 +0530
> @@ -11,17 +11,16 @@
>   */
>  
>  struct writeback_control;
> -typedef int (writepage_t)(struct page *page, struct writeback_control *wbc);
>  
>  int mpage_readpages(struct address_space *mapping, struct list_head *pages,
>  				unsigned nr_pages, get_block_t get_block);
>  int mpage_readpage(struct page *page, get_block_t get_block);
>  int mpage_writepages(struct address_space *mapping,
> -		struct writeback_control *wbc, get_block_t get_block);
> -int mpage_writepage(struct page *page, get_block_t *get_block,
> -		struct writeback_control *wbc);
> +		struct writeback_control *wbc, get_blocks_t get_blocks);
> +int mpage_writepage(struct page *page, get_blocks_t *get_blocks,
> +		struct writeback_control *wbc, writepage_t writepage);
>  int __mpage_writepages(struct address_space *mapping,
> -		struct writeback_control *wbc, get_block_t get_block,
> +		struct writeback_control *wbc, get_blocks_t get_blocks,
>  		writepage_t writepage);
>  
>  static inline int
> diff -urp -X dontdiff linux-2.6.12-rc3/include/linux/pagemap.h linux-2.6.12-rc3-getblocks/include/linux/pagemap.h
> --- linux-2.6.12-rc3/include/linux/pagemap.h	2005-04-21 05:33:16.000000000 +0530
> +++ linux-2.6.12-rc3-getblocks/include/linux/pagemap.h	2005-04-22 15:08:33.000000000 +0530
> @@ -73,7 +73,8 @@ extern struct page * find_or_create_page
>  unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
>  			unsigned int nr_pages, struct page **pages);
>  unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
> -			int tag, unsigned int nr_pages, struct page **pages);
> +			int tag, unsigned int nr_pages, struct page **pages,
> +			int contig);
>  
>  /*
>   * Returns locked page at given index in given cache, creating it if needed.
> diff -urp -X dontdiff linux-2.6.12-rc3/include/linux/pagevec.h linux-2.6.12-rc3-getblocks/include/linux/pagevec.h
> --- linux-2.6.12-rc3/include/linux/pagevec.h	2005-04-21 05:33:16.000000000 +0530
> +++ linux-2.6.12-rc3-getblocks/include/linux/pagevec.h	2005-04-22 15:08:33.000000000 +0530
> @@ -28,6 +28,9 @@ unsigned pagevec_lookup(struct pagevec *
>  unsigned pagevec_lookup_tag(struct pagevec *pvec,
>  		struct address_space *mapping, pgoff_t *index, int tag,
>  		unsigned nr_pages);
> +unsigned pagevec_contig_lookup_tag(struct pagevec *pvec,
> +		struct address_space *mapping, pgoff_t *index, int tag,
> +		unsigned nr_pages);
>  
>  static inline void pagevec_init(struct pagevec *pvec, int cold)
>  {
> diff -urp -X dontdiff linux-2.6.12-rc3/include/linux/radix-tree.h linux-2.6.12-rc3-getblocks/include/linux/radix-tree.h
> --- linux-2.6.12-rc3/include/linux/radix-tree.h	2005-04-21 05:33:16.000000000 +0530
> +++ linux-2.6.12-rc3-getblocks/include/linux/radix-tree.h	2005-04-22 15:08:33.000000000 +0530
> @@ -59,8 +59,18 @@ void *radix_tree_tag_clear(struct radix_
>  int radix_tree_tag_get(struct radix_tree_root *root,
>  			unsigned long index, int tag);
>  unsigned int
> -radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
> -		unsigned long first_index, unsigned int max_items, int tag);
> +__radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
> +		unsigned long first_index, unsigned int max_items, int tag,
> +		int contig);
> +
> +static inline unsigned int radix_tree_gang_lookup_tag(struct radix_tree_root
> +		*root, void **results, unsigned long first_index,
> +		unsigned int max_items, int tag)
> +{
> +	return __radix_tree_gang_lookup_tag(root, results, first_index,
> +		max_items, tag, 0);
> +}
> +
>  int radix_tree_tagged(struct radix_tree_root *root, int tag);
>  
>  static inline void radix_tree_preload_end(void)
> diff -urp -X dontdiff linux-2.6.12-rc3/lib/radix-tree.c linux-2.6.12-rc3-getblocks/lib/radix-tree.c
> --- linux-2.6.12-rc3/lib/radix-tree.c	2005-04-21 05:33:16.000000000 +0530
> +++ linux-2.6.12-rc3-getblocks/lib/radix-tree.c	2005-04-22 16:34:29.000000000 +0530
> @@ -557,12 +557,13 @@ EXPORT_SYMBOL(radix_tree_gang_lookup);
>   */
>  static unsigned int
>  __lookup_tag(struct radix_tree_root *root, void **results, unsigned long index,
> -	unsigned int max_items, unsigned long *next_index, int tag)
> +	unsigned int max_items, unsigned long *next_index, int tag, int contig)
>  {
>  	unsigned int nr_found = 0;
>  	unsigned int shift;
>  	unsigned int height = root->height;
>  	struct radix_tree_node *slot;
> +	unsigned long cindex = (contig && (*next_index)) ? *next_index : -1;
>  
>  	shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
>  	slot = root->rnode;
> @@ -575,6 +576,11 @@ __lookup_tag(struct radix_tree_root *roo
>  				BUG_ON(slot->slots[i] == NULL);
>  				break;
>  			}
> +			if (contig && index >= cindex) {
> +				/* break in contiguity */
> +				index = 0;
> +				goto out;
> +			}
>  			index &= ~((1UL << shift) - 1);
>  			index += 1UL << shift;
>  			if (index == 0)
> @@ -593,6 +599,10 @@ __lookup_tag(struct radix_tree_root *roo
>  					results[nr_found++] = slot->slots[j];
>  					if (nr_found == max_items)
>  						goto out;
> +				} else if (contig && nr_found) {
> +					/* break in contiguity */
> +					index = 0;
> +					goto out;
>  				}
>  			}
>  		}
> @@ -618,29 +628,32 @@ out:
>   *	returns the number of items which were placed at *@results.
>   */
>  unsigned int
> -radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
> -		unsigned long first_index, unsigned int max_items, int tag)
> +__radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
> +		unsigned long first_index, unsigned int max_items, int tag,
> +		int contig)
>  {
>  	const unsigned long max_index = radix_tree_maxindex(root->height);
>  	unsigned long cur_index = first_index;
> +	unsigned long next_index = 0;	/* Index of next contiguous search */
>  	unsigned int ret = 0;
>  
>  	while (ret < max_items) {
>  		unsigned int nr_found;
> -		unsigned long next_index;	/* Index of next search */
>  
>  		if (cur_index > max_index)
>  			break;
>  		nr_found = __lookup_tag(root, results + ret, cur_index,
> -					max_items - ret, &next_index, tag);
> +				max_items - ret, &next_index, tag, contig);
>  		ret += nr_found;
>  		if (next_index == 0)
>  			break;
>  		cur_index = next_index;
> +		if (!nr_found)
> +			next_index = 0;
>  	}
>  	return ret;
>  }
> -EXPORT_SYMBOL(radix_tree_gang_lookup_tag);
> +EXPORT_SYMBOL(__radix_tree_gang_lookup_tag);
>  
>  /**
>   *	radix_tree_delete    -    delete an item from a radix tree
> diff -urp -X dontdiff linux-2.6.12-rc3/mm/filemap.c linux-2.6.12-rc3-getblocks/mm/filemap.c
> --- linux-2.6.12-rc3/mm/filemap.c	2005-04-21 05:33:16.000000000 +0530
> +++ linux-2.6.12-rc3-getblocks/mm/filemap.c	2005-04-22 16:20:30.000000000 +0530
> @@ -635,16 +635,19 @@ unsigned find_get_pages(struct address_s
>  /*
>   * Like find_get_pages, except we only return pages which are tagged with
>   * `tag'.   We update *index to index the next page for the traversal.
> + * If 'contig' is 1, then we return only pages which are contiguous in the
> + * file.
>   */
>  unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
> -			int tag, unsigned int nr_pages, struct page **pages)
> +			int tag, unsigned int nr_pages, struct page **pages,
> +			int contig)
>  {
>  	unsigned int i;
>  	unsigned int ret;
>  
>  	read_lock_irq(&mapping->tree_lock);
> -	ret = radix_tree_gang_lookup_tag(&mapping->page_tree,
> -				(void **)pages, *index, nr_pages, tag);
> +	ret = __radix_tree_gang_lookup_tag(&mapping->page_tree,
> +			(void **)pages, *index, nr_pages, tag, contig);
>  	for (i = 0; i < ret; i++)
>  		page_cache_get(pages[i]);
>  	if (ret)
> diff -urp -X dontdiff linux-2.6.12-rc3/mm/swap.c linux-2.6.12-rc3-getblocks/mm/swap.c
> --- linux-2.6.12-rc3/mm/swap.c	2005-04-21 05:33:16.000000000 +0530
> +++ linux-2.6.12-rc3-getblocks/mm/swap.c	2005-04-22 15:08:33.000000000 +0530
> @@ -384,7 +384,16 @@ unsigned pagevec_lookup_tag(struct pagev
>  		pgoff_t *index, int tag, unsigned nr_pages)
>  {
>  	pvec->nr = find_get_pages_tag(mapping, index, tag,
> -					nr_pages, pvec->pages);
> +					nr_pages, pvec->pages, 0);
> +	return pagevec_count(pvec);
> +}
> +
> +unsigned int
> +pagevec_contig_lookup_tag(struct pagevec *pvec, struct address_space *mapping,
> +		pgoff_t *index, int tag, unsigned nr_pages)
> +{
> +	pvec->nr = find_get_pages_tag(mapping, index, tag,
> +					nr_pages, pvec->pages, 1);
>  	return pagevec_count(pvec);
>  }
>  
> -
> To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
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> 



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Re: [RFC] Adding multiple block allocation

[Mingming Cao]

Oops, sorry about the empty message ...

> -static int ext3_writepages_get_block(struct inode *inode, sector_t iblock,
> -			struct buffer_head *bh, int create)
> +static int ext3_writepages_get_blocks(struct inode *inode, sector_t iblock,
> +		unsigned long max_blocks, struct buffer_head *bh, int create)
>  {
> -	return ext3_direct_io_get_blocks(inode, iblock, 1, bh, create);
> +	return ext3_direct_io_get_blocks(inode, iblock, max_blocks, bh, create);
>  }
>  

I have a question here, ext3_direct_io_get_blocks use DIO_CREDITS
(EXT3_RESERVE_TRANS_BLOCKS + 32 = ) to reserve the space for
journalling, but it seems based on assumption of one data block update
once a time. Is it sufficent to re-use that routine for multiple block
allocation here? Don't we need something like
ext3_writepage_trans_blocks() here?

Thanks,
Mingming



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Re: [Ext2-devel] [RFC] Adding multiple block allocation

[Suparna Bhattacharya]

On Fri, Apr 29, 2005 at 05:44:26PM -0700, Mingming Cao wrote:
> Oops, sorry about the empty message ...
> 
> > -static int ext3_writepages_get_block(struct inode *inode, sector_t iblock,
> > -			struct buffer_head *bh, int create)
> > +static int ext3_writepages_get_blocks(struct inode *inode, sector_t iblock,
> > +		unsigned long max_blocks, struct buffer_head *bh, int create)
> >  {
> > -	return ext3_direct_io_get_blocks(inode, iblock, 1, bh, create);
> > +	return ext3_direct_io_get_blocks(inode, iblock, max_blocks, bh, create);
> >  }
> >  
> 
> I have a question here, ext3_direct_io_get_blocks use DIO_CREDITS
> (EXT3_RESERVE_TRANS_BLOCKS + 32 = ) to reserve the space for
> journalling, but it seems based on assumption of one data block update
> once a time. Is it sufficent to re-use that routine for multiple block
> allocation here? Don't we need something like
> ext3_writepage_trans_blocks() here?

Quite likely - with your patch, as get_blocks actually allocates
multiple blocks at a time, the min credits estimate would 
change for ext3_direct_io_get_blocks/ext3_writepages_get_blocks.

Regards
Suparna

> 
> Thanks,
> Mingming
> 
> 
> 
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> _______________________________________________
> Ext2-devel mailing list
> Ext2-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/ext2-devel

-- 
Suparna Bhattacharya (suparna@in.ibm.com)
Linux Technology Center
IBM Software Lab, India