[PATCH] split generic_file_aio_write into buffered and direct I/O parts

[Christoph Hellwig <hch@lst.de>]

If the generic code falls back to buffered I/O on a hole XFS needs to
relock, so we need to have separate functions to call unless we want to
duplicate everything.   The XFS patch still needs some cleaning up, but
I'll try to get it in before 2.6.8.


--- 1.336/include/linux/fs.h	2004-07-11 11:23:27 +02:00
+++ edited/include/linux/fs.h	2004-07-11 23:14:41 +02:00
@@ -1405,7 +1404,11 @@
 extern ssize_t __generic_file_aio_read(struct kiocb *, const struct iovec *, unsigned long, loff_t *);
 extern ssize_t generic_file_aio_write(struct kiocb *, const char __user *, size_t, loff_t);
 extern ssize_t generic_file_aio_write_nolock(struct kiocb *, const struct iovec *,
-				unsigned long, loff_t *);
+		unsigned long, loff_t *);
+extern ssize_t generic_file_direct_write(struct kiocb *, const struct iovec *,
+		unsigned long *, loff_t, loff_t *, size_t, size_t);
+extern ssize_t generic_file_buffered_write(struct kiocb *, const struct iovec *,
+		unsigned long, loff_t, loff_t *, size_t, ssize_t);
 extern ssize_t do_sync_read(struct file *filp, char __user *buf, size_t len, loff_t *ppos);
 extern ssize_t do_sync_write(struct file *filp, const char __user *buf, size_t len, loff_t *ppos);
 ssize_t generic_file_write_nolock(struct file *file, const struct iovec *iov,
--- 1.258/mm/filemap.c	2004-07-11 10:52:25 +02:00
+++ edited/mm/filemap.c	2004-07-11 23:13:52 +02:00
@@ -1812,116 +1812,64 @@
 
 EXPORT_SYMBOL(generic_write_checks);
 
-/*
- * Write to a file through the page cache. 
- * Called under i_sem for S_ISREG files.
- *
- * We put everything into the page cache prior to writing it. This is not a
- * problem when writing full pages. With partial pages, however, we first have
- * to read the data into the cache, then dirty the page, and finally schedule
- * it for writing by marking it dirty.
- *							okir@monad.swb.de
- */
 ssize_t
-generic_file_aio_write_nolock(struct kiocb *iocb, const struct iovec *iov,
-				unsigned long nr_segs, loff_t *ppos)
+generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
+		unsigned long *nr_segs, loff_t pos, loff_t *ppos,
+		size_t count, size_t ocount)
+{
+	struct file	*file = iocb->ki_filp;
+	struct address_space *mapping = file->f_mapping;
+	struct inode	*inode = mapping->host;
+	ssize_t		written;
+
+	if (count != ocount)
+		*nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count);
+
+	written = generic_file_direct_IO(WRITE, iocb, iov, pos, *nr_segs);
+	if (written > 0) {
+		loff_t end = pos + written;
+		if (end > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
+			i_size_write(inode,  end);
+			mark_inode_dirty(inode);
+		}
+		*ppos = end;
+	}
+
+	/*
+	 * Sync the fs metadata but not the minor inode changes and
+	 * of course not the data as we did direct DMA for the IO.
+	 * i_sem is held, which protects generic_osync_inode() from
+	 * livelocking.
+	 */
+	if (written >= 0 && file->f_flags & O_SYNC)
+		generic_osync_inode(inode, mapping, OSYNC_METADATA);
+	if (written == count && !is_sync_kiocb(iocb))
+		written = -EIOCBQUEUED;
+	return written;
+}
+
+EXPORT_SYMBOL(generic_file_direct_write);
+	
+ssize_t
+generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
+		unsigned long nr_segs, loff_t pos, loff_t *ppos,
+		size_t count, ssize_t written)
 {
 	struct file *file = iocb->ki_filp;
 	struct address_space * mapping = file->f_mapping;
 	struct address_space_operations *a_ops = mapping->a_ops;
-	size_t ocount;		/* original count */
-	size_t count;		/* after file limit checks */
 	struct inode 	*inode = mapping->host;
 	long		status = 0;
-	loff_t		pos;
 	struct page	*page;
 	struct page	*cached_page = NULL;
-	const int	isblk = S_ISBLK(inode->i_mode);
-	ssize_t		written;
-	ssize_t		err;
 	size_t		bytes;
 	struct pagevec	lru_pvec;
 	const struct iovec *cur_iov = iov; /* current iovec */
 	size_t		iov_base = 0;	   /* offset in the current iovec */
-	unsigned long	seg;
 	char __user	*buf;
 
-	ocount = 0;
-	for (seg = 0; seg < nr_segs; seg++) {
-		const struct iovec *iv = &iov[seg];
-
-		/*
-		 * If any segment has a negative length, or the cumulative
-		 * length ever wraps negative then return -EINVAL.
-		 */
-		ocount += iv->iov_len;
-		if (unlikely((ssize_t)(ocount|iv->iov_len) < 0))
-			return -EINVAL;
-		if (access_ok(VERIFY_READ, iv->iov_base, iv->iov_len))
-			continue;
-		if (seg == 0)
-			return -EFAULT;
-		nr_segs = seg;
-		ocount -= iv->iov_len;	/* This segment is no good */
-		break;
-	}
-
-	count = ocount;
-	pos = *ppos;
 	pagevec_init(&lru_pvec, 0);
 
-	/* We can write back this queue in page reclaim */
-	current->backing_dev_info = mapping->backing_dev_info;
-	written = 0;
-
-	err = generic_write_checks(file, &pos, &count, isblk);
-	if (err)
-		goto out;
-
-	if (count == 0)
-		goto out;
-
-	err = remove_suid(file->f_dentry);
-	if (err)
-		goto out;
-
-	inode_update_time(inode, 1);
-
-	/* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
-	if (unlikely(file->f_flags & O_DIRECT)) {
-		if (count != ocount)
-			nr_segs = iov_shorten((struct iovec *)iov,
-						nr_segs, count);
-		written = generic_file_direct_IO(WRITE, iocb,
-					iov, pos, nr_segs);
-		if (written > 0) {
-			loff_t end = pos + written;
-			if (end > i_size_read(inode) && !isblk) {
-				i_size_write(inode,  end);
-				mark_inode_dirty(inode);
-			}
-			*ppos = end;
-		}
-		/*
-		 * Sync the fs metadata but not the minor inode changes and
-		 * of course not the data as we did direct DMA for the IO.
-		 * i_sem is held, which protects generic_osync_inode() from
-		 * livelocking.
-		 */
-		if (written >= 0 && file->f_flags & O_SYNC)
-			status = generic_osync_inode(inode, mapping, OSYNC_METADATA);
-		if (written == count && !is_sync_kiocb(iocb))
-			written = -EIOCBQUEUED;
-		if (written < 0 || written == count)
-			goto out_status;
-		/*
-		 * direct-io write to a hole: fall through to buffered I/O
-		 * for completing the rest of the request.
-		 */
-		pos += written;
-		count -= written;
-	}
-
 	buf = iov->iov_base + written;	/* handle partial DIO write */
 	do {
 		unsigned long index;
@@ -2016,12 +1964,85 @@
 	if (unlikely(file->f_flags & O_DIRECT) && written)
 		status = filemap_write_and_wait(mapping);
 
-out_status:	
-	err = written ? written : status;
-out:
 	pagevec_lru_add(&lru_pvec);
+	return written ? written : status;
+}
+
+EXPORT_SYMBOL(generic_file_buffered_write);
+
+ssize_t
+generic_file_aio_write_nolock(struct kiocb *iocb, const struct iovec *iov,
+				unsigned long nr_segs, loff_t *ppos)
+{
+	struct file *file = iocb->ki_filp;
+	struct address_space * mapping = file->f_mapping;
+	size_t ocount;		/* original count */
+	size_t count;		/* after file limit checks */
+	struct inode 	*inode = mapping->host;
+	unsigned long	seg;
+	loff_t		pos;
+	ssize_t		written;
+	ssize_t		err;
+
+	ocount = 0;
+	for (seg = 0; seg < nr_segs; seg++) {
+		const struct iovec *iv = &iov[seg];
+
+		/*
+		 * If any segment has a negative length, or the cumulative
+		 * length ever wraps negative then return -EINVAL.
+		 */
+		ocount += iv->iov_len;
+		if (unlikely((ssize_t)(ocount|iv->iov_len) < 0))
+			return -EINVAL;
+		if (access_ok(VERIFY_READ, iv->iov_base, iv->iov_len))
+			continue;
+		if (seg == 0)
+			return -EFAULT;
+		nr_segs = seg;
+		ocount -= iv->iov_len;	/* This segment is no good */
+		break;
+	}
+
+	count = ocount;
+	pos = *ppos;
+
+	/* We can write back this queue in page reclaim */
+	current->backing_dev_info = mapping->backing_dev_info;
+	written = 0;
+
+	err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
+	if (err)
+		goto out;
+
+	if (count == 0)
+		goto out;
+
+	err = remove_suid(file->f_dentry);
+	if (err)
+		goto out;
+
+	inode_update_time(inode, 1);
+
+	/* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
+	if (unlikely(file->f_flags & O_DIRECT)) {
+		written = generic_file_direct_write(iocb, iov,
+				&nr_segs, pos, ppos, count, ocount);
+		if (written < 0 || written == count)
+			goto out;
+		/*
+		 * direct-io write to a hole: fall through to buffered I/O
+		 * for completing the rest of the request.
+		 */
+		pos += written;
+		count -= written;
+	}
+
+	written = generic_file_buffered_write(iocb, iov, nr_segs,
+			pos, ppos, count, written);
+out:
 	current->backing_dev_info = NULL;
-	return err;
+	return written ? written : err;
 }
 
 EXPORT_SYMBOL(generic_file_aio_write_nolock);