[PATCH 4/4] reiserfs: on-demand bitmap loading

[PATCH 4/4] reiserfs: on-demand bitmap loading

[Jeff Mahoney]

 This is the patch the three previous ones have been leading up to.

 It changes the behavior of ReiserFS from loading and caching all the bitmaps
 as special, to treating the bitmaps like any other bit of metadata and just
 letting the system-wide caches figure out what to hang on to.

 Buffer heads are allocated on the fly, so there is no need to retain pointers
 to all of them. The caching of the metadata occurs when the data is read
 and updated, and is considered invalid and uncached until then.

 fs/reiserfs/bitmap.c           |   76 ++++++++++++++++++++---------------------
 fs/reiserfs/resize.c           |   24 +++++++++---
 fs/reiserfs/super.c            |   25 -------------
 include/linux/reiserfs_fs_sb.h |    1 
 4 files changed, 56 insertions(+), 70 deletions(-)

Signed-off-by: Jeff Mahoney <jeffm@suse.com>

diff -ruNpX ../dontdiff linux-2.6.15.orig.staging1/fs/reiserfs/bitmap.c linux-2.6.15.orig.staging2/fs/reiserfs/bitmap.c
--- linux-2.6.15.orig.staging1/fs/reiserfs/bitmap.c	2006-01-16 16:53:33.626628760 -0500
+++ linux-2.6.15.orig.staging2/fs/reiserfs/bitmap.c	2006-01-16 16:53:33.634627544 -0500
@@ -101,8 +101,9 @@ int is_reusable(struct super_block *s, b
 		return 0;
 	}
 
-	bh = SB_AP_BITMAP(s)[i].bh;
-	get_bh(bh);
+	bh = reiserfs_read_bitmap_block(s, bmap);
+	if (bh == NULL)
+		return 0;
 
 	if ((bit_value == 0 && reiserfs_test_le_bit(j, bh->b_data)) ||
 	    (bit_value == 1 && reiserfs_test_le_bit(j, bh->b_data) == 0)) {
@@ -175,13 +176,10 @@ static int scan_bitmap_block(struct reis
 				 bmap_n);
 		return 0;
 	}
-	bh = bi->bh;
-	get_bh(bh);
 
-	if (buffer_locked(bi->bh)) {
-		PROC_INFO_INC(s, scan_bitmap.wait);
-		__wait_on_buffer(bh);
-	}
+	bh = reiserfs_read_bitmap_block(s, bmap_n);
+	if (bh == NULL)
+		return 0;
 
 	while (1) {
 		if (bi->free_count < min) {
@@ -286,9 +284,20 @@ static int bmap_hash_id(struct super_blo
  */
 static inline int block_group_used(struct super_block *s, u32 id)
 {
-	int bm;
-	bm = bmap_hash_id(s, id);
-	if (SB_AP_BITMAP(s)[bm].free_count > ((s->s_blocksize << 3) * 60 / 100)) {
+	int bm = bmap_hash_id(s, id);
+	struct reiserfs_bitmap_info *info = &SB_AP_BITMAP(s)[bm];
+
+	/* If we don't have cached information on this bitmap block, we're
+	 * going to have to load it later anyway. Loading it here allows us
+	 * to make a better decision. This favors long-term performace gain
+	 * with a better on-disk layout vs. a short term gain of skipping the
+	 * read and potentially having a bad placement. */
+	if (info->first_zero_hint == 0) {
+		struct buffer_head *bh = reiserfs_read_bitmap_block(s, bm);
+		brelse(bh);
+	}
+
+	if (info->free_count > ((s->s_blocksize << 3) * 60 / 100)) {
 		return 0;
 	}
 	return 1;
@@ -414,8 +423,9 @@ static void _reiserfs_free_block(struct 
 		return;
 	}
 
-	bmbh = apbi[nr].bh;
-	get_bh(bmbh);
+	bmbh = reiserfs_read_bitmap_block(s, nr);
+	if (!bmbh)
+		return;
 
 	reiserfs_prepare_for_journal(s, bmbh, 1);
 
@@ -1319,6 +1329,7 @@ struct buffer_head *reiserfs_read_bitmap
                                                unsigned int bitmap)
 {
 	unsigned int block = (sb->s_blocksize << 3) * bitmap;
+	struct reiserfs_bitmap_info *info = SB_AP_BITMAP(sb) + bitmap;
 	struct buffer_head *bh;
 
 	/* Way old format filesystems had the bitmaps packed up front.
@@ -1326,9 +1337,20 @@ struct buffer_head *reiserfs_read_bitmap
 	if (test_bit(REISERFS_OLD_FORMAT, &(REISERFS_SB(sb)->s_properties)))
 		block = REISERFS_SB(sb)->s_sbh->b_blocknr + 1 + bitmap;
 
-	bh = sb_getblk(sb, block);
-	if (!buffer_uptodate(bh))
-		ll_rw_block(READ, 1, &bh);
+	bh = sb_bread(sb, block);
+	if (bh == NULL)
+		reiserfs_warning(sb, "sh-2029: reiserfs read_bitmaps: "
+				 "bitmap block (#%lu) reading failed",
+				 bh->b_blocknr);
+	else {
+		if (buffer_locked(bh)) {
+			PROC_INFO_INC(s, scan_bitmap.wait);
+			__wait_on_buffer(bh);
+		}
+		
+		if (info->first_zero_hint == 0)
+			reiserfs_cache_bitmap_metadata(sb, bh, info);
+	}
 
 	return bh;
 }
@@ -1336,7 +1358,6 @@ struct buffer_head *reiserfs_read_bitmap
 int reiserfs_init_bitmap_cache(struct super_block *sb)
 {
 	struct reiserfs_bitmap_info *bitmap;
-	int i;
 
 	bitmap = vmalloc(sizeof (*bitmap) * SB_BMAP_NR(sb));
 	if (bitmap == NULL)
@@ -1344,27 +1365,6 @@ int reiserfs_init_bitmap_cache(struct su
 
 	memset(bitmap, 0, sizeof (*bitmap) * SB_BMAP_NR(sb));
 
-	for (i = 0; i < SB_BMAP_NR(sb); i++)
-		bitmap[i].bh = reiserfs_read_bitmap_block(sb, i);
-
-	/* make sure we have them all */
-	for (i = 0; i < SB_BMAP_NR(sb); i++) {
-		wait_on_buffer(bitmap[i].bh);
-		if (!buffer_uptodate(bitmap[i].bh)) {
-			reiserfs_warning(sb, "sh-2029: reiserfs read_bitmaps: "
-					 "bitmap block (#%lu) reading failed",
-					 bitmap[i].bh->b_blocknr);
-			for (i = 0; i < SB_BMAP_NR(sb); i++)
-				brelse(bitmap[i].bh);
-			vfree(bitmap);
-			return 1;
-		}
-	}
-
-	/* Cache the info on the bitmaps before we get rolling */
-	for (i = 0; i < SB_BMAP_NR(sb); i++)
-		reiserfs_cache_bitmap_metadata(sb, bitmap[i].bh, &bitmap[i]);
-
 	SB_AP_BITMAP(sb) = bitmap;
 
 	return 0;
diff -ruNpX ../dontdiff linux-2.6.15.orig.staging1/fs/reiserfs/resize.c linux-2.6.15.orig.staging2/fs/reiserfs/resize.c
--- linux-2.6.15.orig.staging1/fs/reiserfs/resize.c	2006-01-16 16:53:33.626628760 -0500
+++ linux-2.6.15.orig.staging2/fs/reiserfs/resize.c	2006-01-16 16:53:33.636627240 -0500
@@ -128,8 +128,9 @@ int reiserfs_resize(struct super_block *
 		 * transaction begins, and the new bitmaps don't matter if the
 		 * transaction fails. */
 		for (i = bmap_nr; i < bmap_nr_new; i++) {
-			bh = sb_getblk(s, i * s->s_blocksize * 8);
-			get_bh(bh);
+			/* don't use read_bitmap_block since it will cache
+			 * the uninitialized bitmap */
+			bh = sb_bread(s, i * s->s_blocksize * 8);
 			memset(bh->b_data, 0, sb_blocksize(sb));
 			reiserfs_test_and_set_le_bit(0, bh->b_data);
 			reiserfs_cache_bitmap_metadata(s, bh, bitmap + i);
@@ -140,7 +141,6 @@ int reiserfs_resize(struct super_block *
 			// update bitmap_info stuff
 			bitmap[i].first_zero_hint = 1;
 			bitmap[i].free_count = sb_blocksize(sb) * 8 - 1;
-			bitmap[i].bh = bh;
 			brelse(bh);
 		}
 		/* free old bitmap blocks array */
@@ -157,8 +157,13 @@ int reiserfs_resize(struct super_block *
 
 	/* Extend old last bitmap block - new blocks have been made available */
 	info = SB_AP_BITMAP(s) + bmap_nr - 1;
-	bh = info->bh;
-	get_bh(bh);
+	bh = reiserfs_read_bitmap_block(s, bmap_nr - 1);
+	if (!bh) {
+		int jerr = journal_end(&th, s, 10);
+		if (jerr)
+			return jerr;
+		return -EIO;
+	}
 
 	reiserfs_prepare_for_journal(s, bh, 1);
 	for (i = block_r; i < s->s_blocksize * 8; i++)
@@ -172,8 +177,13 @@ int reiserfs_resize(struct super_block *
 
 	/* Correct new last bitmap block - It may not be full */
 	info = SB_AP_BITMAP(s) + bmap_nr_new - 1;
-	bh = info->bh;
-	get_bh(bh);
+	bh = reiserfs_read_bitmap_block(s, bmap_nr_new - 1);
+	if (!bh) {
+		int jerr = journal_end(&th, s, 10);
+		if (jerr)
+			return jerr;
+		return -EIO;
+	}
 
 	reiserfs_prepare_for_journal(s, bh, 1);
 	for (i = block_r_new; i < s->s_blocksize * 8; i++)
diff -ruNpX ../dontdiff linux-2.6.15.orig.staging1/fs/reiserfs/super.c linux-2.6.15.orig.staging2/fs/reiserfs/super.c
--- linux-2.6.15.orig.staging1/fs/reiserfs/super.c	2006-01-16 16:53:33.628628456 -0500
+++ linux-2.6.15.orig.staging2/fs/reiserfs/super.c	2006-01-16 16:53:33.637627088 -0500
@@ -433,7 +433,6 @@ int remove_save_link(struct inode *inode
 
 static void reiserfs_put_super(struct super_block *s)
 {
-	int i;
 	struct reiserfs_transaction_handle th;
 	th.t_trans_id = 0;
 
@@ -463,9 +462,6 @@ static void reiserfs_put_super(struct su
 	 */
 	journal_release(&th, s);
 
-	for (i = 0; i < SB_BMAP_NR(s); i++)
-		brelse(SB_AP_BITMAP(s)[i].bh);
-
 	vfree(SB_AP_BITMAP(s));
 
 	brelse(SB_BUFFER_WITH_SB(s));
@@ -1365,7 +1361,6 @@ static int read_super_block(struct super
 /* after journal replay, reread all bitmap and super blocks */
 static int reread_meta_blocks(struct super_block *s)
 {
-	int i;
 	ll_rw_block(READ, 1, &(SB_BUFFER_WITH_SB(s)));
 	wait_on_buffer(SB_BUFFER_WITH_SB(s));
 	if (!buffer_uptodate(SB_BUFFER_WITH_SB(s))) {
@@ -1374,20 +1369,7 @@ static int reread_meta_blocks(struct sup
 		return 1;
 	}
 
-	for (i = 0; i < SB_BMAP_NR(s); i++) {
-		ll_rw_block(READ, 1, &(SB_AP_BITMAP(s)[i].bh));
-		wait_on_buffer(SB_AP_BITMAP(s)[i].bh);
-		if (!buffer_uptodate(SB_AP_BITMAP(s)[i].bh)) {
-			reiserfs_warning(s,
-					 "reread_meta_blocks, error reading bitmap block number %d at %llu",
-					 i,
-					 (unsigned long long)SB_AP_BITMAP(s)[i].
-					 bh->b_blocknr);
-			return 1;
-		}
-	}
 	return 0;
-
 }
 
 /////////////////////////////////////////////////////
@@ -1814,13 +1796,8 @@ static int reiserfs_fill_super(struct su
 	if (jinit_done) {	/* kill the commit thread, free journal ram */
 		journal_release_error(NULL, s);
 	}
-	if (SB_DISK_SUPER_BLOCK(s)) {
-		for (j = 0; j < SB_BMAP_NR(s); j++) {
-			if (SB_AP_BITMAP(s))
-				brelse(SB_AP_BITMAP(s)[j].bh);
-		}
+	if (SB_DISK_SUPER_BLOCK(s))
 		vfree(SB_AP_BITMAP(s));
-	}
 	if (SB_BUFFER_WITH_SB(s))
 		brelse(SB_BUFFER_WITH_SB(s));
 #ifdef CONFIG_QUOTA
diff -ruNpX ../dontdiff linux-2.6.15.orig.staging1/include/linux/reiserfs_fs_sb.h linux-2.6.15.orig.staging2/include/linux/reiserfs_fs_sb.h
--- linux-2.6.15.orig.staging1/include/linux/reiserfs_fs_sb.h	2006-01-16 16:53:29.453263208 -0500
+++ linux-2.6.15.orig.staging2/include/linux/reiserfs_fs_sb.h	2006-01-16 16:53:33.638626936 -0500
@@ -267,7 +267,6 @@ struct reiserfs_bitmap_info {
 	// FIXME: Won't work with block sizes > 8K
 	__u16 first_zero_hint;
 	__u16 free_count;
-	struct buffer_head *bh;	/* the actual bitmap */
 };
 
 struct proc_dir_entry;

Re: [PATCH 4/4] reiserfs: on-demand bitmap loading

[Hans Reiser]

Are you saying that you allow bitmaps to be unloaded?  If yes, how about
making that a separate option, and not the default?

Hans

Jeff Mahoney wrote:

> This is the patch the three previous ones have been leading up to.
>
> It changes the behavior of ReiserFS from loading and caching all the bitmaps
> as special, to treating the bitmaps like any other bit of metadata and just
> letting the system-wide caches figure out what to hang on to.
>
> Buffer heads are allocated on the fly, so there is no need to retain pointers
> to all of them. The caching of the metadata occurs when the data is read
> and updated, and is considered invalid and uncached until then.
>
> fs/reiserfs/bitmap.c           |   76 ++++++++++++++++++++---------------------
> fs/reiserfs/resize.c           |   24 +++++++++---
> fs/reiserfs/super.c            |   25 -------------
> include/linux/reiserfs_fs_sb.h |    1 
> 4 files changed, 56 insertions(+), 70 deletions(-)
>
>Signed-off-by: Jeff Mahoney <jeffm@suse.com>
>
>diff -ruNpX ../dontdiff linux-2.6.15.orig.staging1/fs/reiserfs/bitmap.c linux-2.6.15.orig.staging2/fs/reiserfs/bitmap.c
>--- linux-2.6.15.orig.staging1/fs/reiserfs/bitmap.c	2006-01-16 16:53:33.626628760 -0500
>+++ linux-2.6.15.orig.staging2/fs/reiserfs/bitmap.c	2006-01-16 16:53:33.634627544 -0500
>@@ -101,8 +101,9 @@ int is_reusable(struct super_block *s, b
> 		return 0;
> 	}
> 
>-	bh = SB_AP_BITMAP(s)[i].bh;
>-	get_bh(bh);
>+	bh = reiserfs_read_bitmap_block(s, bmap);
>+	if (bh == NULL)
>+		return 0;
> 
> 	if ((bit_value == 0 && reiserfs_test_le_bit(j, bh->b_data)) ||
> 	    (bit_value == 1 && reiserfs_test_le_bit(j, bh->b_data) == 0)) {
>@@ -175,13 +176,10 @@ static int scan_bitmap_block(struct reis
> 				 bmap_n);
> 		return 0;
> 	}
>-	bh = bi->bh;
>-	get_bh(bh);
> 
>-	if (buffer_locked(bi->bh)) {
>-		PROC_INFO_INC(s, scan_bitmap.wait);
>-		__wait_on_buffer(bh);
>-	}
>+	bh = reiserfs_read_bitmap_block(s, bmap_n);
>+	if (bh == NULL)
>+		return 0;
> 
> 	while (1) {
> 		if (bi->free_count < min) {
>@@ -286,9 +284,20 @@ static int bmap_hash_id(struct super_blo
>  */
> static inline int block_group_used(struct super_block *s, u32 id)
> {
>-	int bm;
>-	bm = bmap_hash_id(s, id);
>-	if (SB_AP_BITMAP(s)[bm].free_count > ((s->s_blocksize << 3) * 60 / 100)) {
>+	int bm = bmap_hash_id(s, id);
>+	struct reiserfs_bitmap_info *info = &SB_AP_BITMAP(s)[bm];
>+
>+	/* If we don't have cached information on this bitmap block, we're
>+	 * going to have to load it later anyway. Loading it here allows us
>+	 * to make a better decision. This favors long-term performace gain
>+	 * with a better on-disk layout vs. a short term gain of skipping the
>+	 * read and potentially having a bad placement. */
>+	if (info->first_zero_hint == 0) {
>+		struct buffer_head *bh = reiserfs_read_bitmap_block(s, bm);
>+		brelse(bh);
>+	}
>+
>+	if (info->free_count > ((s->s_blocksize << 3) * 60 / 100)) {
> 		return 0;
> 	}
> 	return 1;
>@@ -414,8 +423,9 @@ static void _reiserfs_free_block(struct 
> 		return;
> 	}
> 
>-	bmbh = apbi[nr].bh;
>-	get_bh(bmbh);
>+	bmbh = reiserfs_read_bitmap_block(s, nr);
>+	if (!bmbh)
>+		return;
> 
> 	reiserfs_prepare_for_journal(s, bmbh, 1);
> 
>@@ -1319,6 +1329,7 @@ struct buffer_head *reiserfs_read_bitmap
>                                                unsigned int bitmap)
> {
> 	unsigned int block = (sb->s_blocksize << 3) * bitmap;
>+	struct reiserfs_bitmap_info *info = SB_AP_BITMAP(sb) + bitmap;
> 	struct buffer_head *bh;
> 
> 	/* Way old format filesystems had the bitmaps packed up front.
>@@ -1326,9 +1337,20 @@ struct buffer_head *reiserfs_read_bitmap
> 	if (test_bit(REISERFS_OLD_FORMAT, &(REISERFS_SB(sb)->s_properties)))
> 		block = REISERFS_SB(sb)->s_sbh->b_blocknr + 1 + bitmap;
> 
>-	bh = sb_getblk(sb, block);
>-	if (!buffer_uptodate(bh))
>-		ll_rw_block(READ, 1, &bh);
>+	bh = sb_bread(sb, block);
>+	if (bh == NULL)
>+		reiserfs_warning(sb, "sh-2029: reiserfs read_bitmaps: "
>+				 "bitmap block (#%lu) reading failed",
>+				 bh->b_blocknr);
>+	else {
>+		if (buffer_locked(bh)) {
>+			PROC_INFO_INC(s, scan_bitmap.wait);
>+			__wait_on_buffer(bh);
>+		}
>+		
>+		if (info->first_zero_hint == 0)
>+			reiserfs_cache_bitmap_metadata(sb, bh, info);
>+	}
> 
> 	return bh;
> }
>@@ -1336,7 +1358,6 @@ struct buffer_head *reiserfs_read_bitmap
> int reiserfs_init_bitmap_cache(struct super_block *sb)
> {
> 	struct reiserfs_bitmap_info *bitmap;
>-	int i;
> 
> 	bitmap = vmalloc(sizeof (*bitmap) * SB_BMAP_NR(sb));
> 	if (bitmap == NULL)
>@@ -1344,27 +1365,6 @@ int reiserfs_init_bitmap_cache(struct su
> 
> 	memset(bitmap, 0, sizeof (*bitmap) * SB_BMAP_NR(sb));
> 
>-	for (i = 0; i < SB_BMAP_NR(sb); i++)
>-		bitmap[i].bh = reiserfs_read_bitmap_block(sb, i);
>-
>-	/* make sure we have them all */
>-	for (i = 0; i < SB_BMAP_NR(sb); i++) {
>-		wait_on_buffer(bitmap[i].bh);
>-		if (!buffer_uptodate(bitmap[i].bh)) {
>-			reiserfs_warning(sb, "sh-2029: reiserfs read_bitmaps: "
>-					 "bitmap block (#%lu) reading failed",
>-					 bitmap[i].bh->b_blocknr);
>-			for (i = 0; i < SB_BMAP_NR(sb); i++)
>-				brelse(bitmap[i].bh);
>-			vfree(bitmap);
>-			return 1;
>-		}
>-	}
>-
>-	/* Cache the info on the bitmaps before we get rolling */
>-	for (i = 0; i < SB_BMAP_NR(sb); i++)
>-		reiserfs_cache_bitmap_metadata(sb, bitmap[i].bh, &bitmap[i]);
>-
> 	SB_AP_BITMAP(sb) = bitmap;
> 
> 	return 0;
>diff -ruNpX ../dontdiff linux-2.6.15.orig.staging1/fs/reiserfs/resize.c linux-2.6.15.orig.staging2/fs/reiserfs/resize.c
>--- linux-2.6.15.orig.staging1/fs/reiserfs/resize.c	2006-01-16 16:53:33.626628760 -0500
>+++ linux-2.6.15.orig.staging2/fs/reiserfs/resize.c	2006-01-16 16:53:33.636627240 -0500
>@@ -128,8 +128,9 @@ int reiserfs_resize(struct super_block *
> 		 * transaction begins, and the new bitmaps don't matter if the
> 		 * transaction fails. */
> 		for (i = bmap_nr; i < bmap_nr_new; i++) {
>-			bh = sb_getblk(s, i * s->s_blocksize * 8);
>-			get_bh(bh);
>+			/* don't use read_bitmap_block since it will cache
>+			 * the uninitialized bitmap */
>+			bh = sb_bread(s, i * s->s_blocksize * 8);
> 			memset(bh->b_data, 0, sb_blocksize(sb));
> 			reiserfs_test_and_set_le_bit(0, bh->b_data);
> 			reiserfs_cache_bitmap_metadata(s, bh, bitmap + i);
>@@ -140,7 +141,6 @@ int reiserfs_resize(struct super_block *
> 			// update bitmap_info stuff
> 			bitmap[i].first_zero_hint = 1;
> 			bitmap[i].free_count = sb_blocksize(sb) * 8 - 1;
>-			bitmap[i].bh = bh;
> 			brelse(bh);
> 		}
> 		/* free old bitmap blocks array */
>@@ -157,8 +157,13 @@ int reiserfs_resize(struct super_block *
> 
> 	/* Extend old last bitmap block - new blocks have been made available */
> 	info = SB_AP_BITMAP(s) + bmap_nr - 1;
>-	bh = info->bh;
>-	get_bh(bh);
>+	bh = reiserfs_read_bitmap_block(s, bmap_nr - 1);
>+	if (!bh) {
>+		int jerr = journal_end(&th, s, 10);
>+		if (jerr)
>+			return jerr;
>+		return -EIO;
>+	}
> 
> 	reiserfs_prepare_for_journal(s, bh, 1);
> 	for (i = block_r; i < s->s_blocksize * 8; i++)
>@@ -172,8 +177,13 @@ int reiserfs_resize(struct super_block *
> 
> 	/* Correct new last bitmap block - It may not be full */
> 	info = SB_AP_BITMAP(s) + bmap_nr_new - 1;
>-	bh = info->bh;
>-	get_bh(bh);
>+	bh = reiserfs_read_bitmap_block(s, bmap_nr_new - 1);
>+	if (!bh) {
>+		int jerr = journal_end(&th, s, 10);
>+		if (jerr)
>+			return jerr;
>+		return -EIO;
>+	}
> 
> 	reiserfs_prepare_for_journal(s, bh, 1);
> 	for (i = block_r_new; i < s->s_blocksize * 8; i++)
>diff -ruNpX ../dontdiff linux-2.6.15.orig.staging1/fs/reiserfs/super.c linux-2.6.15.orig.staging2/fs/reiserfs/super.c
>--- linux-2.6.15.orig.staging1/fs/reiserfs/super.c	2006-01-16 16:53:33.628628456 -0500
>+++ linux-2.6.15.orig.staging2/fs/reiserfs/super.c	2006-01-16 16:53:33.637627088 -0500
>@@ -433,7 +433,6 @@ int remove_save_link(struct inode *inode
> 
> static void reiserfs_put_super(struct super_block *s)
> {
>-	int i;
> 	struct reiserfs_transaction_handle th;
> 	th.t_trans_id = 0;
> 
>@@ -463,9 +462,6 @@ static void reiserfs_put_super(struct su
> 	 */
> 	journal_release(&th, s);
> 
>-	for (i = 0; i < SB_BMAP_NR(s); i++)
>-		brelse(SB_AP_BITMAP(s)[i].bh);
>-
> 	vfree(SB_AP_BITMAP(s));
> 
> 	brelse(SB_BUFFER_WITH_SB(s));
>@@ -1365,7 +1361,6 @@ static int read_super_block(struct super
> /* after journal replay, reread all bitmap and super blocks */
> static int reread_meta_blocks(struct super_block *s)
> {
>-	int i;
> 	ll_rw_block(READ, 1, &(SB_BUFFER_WITH_SB(s)));
> 	wait_on_buffer(SB_BUFFER_WITH_SB(s));
> 	if (!buffer_uptodate(SB_BUFFER_WITH_SB(s))) {
>@@ -1374,20 +1369,7 @@ static int reread_meta_blocks(struct sup
> 		return 1;
> 	}
> 
>-	for (i = 0; i < SB_BMAP_NR(s); i++) {
>-		ll_rw_block(READ, 1, &(SB_AP_BITMAP(s)[i].bh));
>-		wait_on_buffer(SB_AP_BITMAP(s)[i].bh);
>-		if (!buffer_uptodate(SB_AP_BITMAP(s)[i].bh)) {
>-			reiserfs_warning(s,
>-					 "reread_meta_blocks, error reading bitmap block number %d at %llu",
>-					 i,
>-					 (unsigned long long)SB_AP_BITMAP(s)[i].
>-					 bh->b_blocknr);
>-			return 1;
>-		}
>-	}
> 	return 0;
>-
> }
> 
> /////////////////////////////////////////////////////
>@@ -1814,13 +1796,8 @@ static int reiserfs_fill_super(struct su
> 	if (jinit_done) {	/* kill the commit thread, free journal ram */
> 		journal_release_error(NULL, s);
> 	}
>-	if (SB_DISK_SUPER_BLOCK(s)) {
>-		for (j = 0; j < SB_BMAP_NR(s); j++) {
>-			if (SB_AP_BITMAP(s))
>-				brelse(SB_AP_BITMAP(s)[j].bh);
>-		}
>+	if (SB_DISK_SUPER_BLOCK(s))
> 		vfree(SB_AP_BITMAP(s));
>-	}
> 	if (SB_BUFFER_WITH_SB(s))
> 		brelse(SB_BUFFER_WITH_SB(s));
> #ifdef CONFIG_QUOTA
>diff -ruNpX ../dontdiff linux-2.6.15.orig.staging1/include/linux/reiserfs_fs_sb.h linux-2.6.15.orig.staging2/include/linux/reiserfs_fs_sb.h
>--- linux-2.6.15.orig.staging1/include/linux/reiserfs_fs_sb.h	2006-01-16 16:53:29.453263208 -0500
>+++ linux-2.6.15.orig.staging2/include/linux/reiserfs_fs_sb.h	2006-01-16 16:53:33.638626936 -0500
>@@ -267,7 +267,6 @@ struct reiserfs_bitmap_info {
> 	// FIXME: Won't work with block sizes > 8K
> 	__u16 first_zero_hint;
> 	__u16 free_count;
>-	struct buffer_head *bh;	/* the actual bitmap */
> };
> 
> struct proc_dir_entry;
>
>
>  
>

Re: [PATCH 4/4] reiserfs: on-demand bitmap loading

[Jeff Mahoney]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Hans Reiser wrote:
> Are you saying that you allow bitmaps to be unloaded?  If yes, how about
> making that a separate option, and not the default?

They're released, yes. Whether or not they're unloaded is up to the rest
of the system, vm pressure, etc to determine. This isn't any different
than the patch I posted before, which you ultimately approved in September.

If the bitmaps are to be pinned at all, I'd prefer to make *that* the
option. ReiserFS's behavior with respect to bitmaps is inconsistent with
every other Linux file system. I'd prefer to make the dynamic bitmaps
the default, and if you really must, add an option to continue to pin them.

The fact remains that the bitmap blocks are infrequently accessed in
comparison with other bits of metadata that we don't pin. They're not
accessed at all in a read-only environment, and barely accessed in a
light-write workload. If the bitmaps are truly in demand for heavy
writing, the caches should keep those blocks in memory, the same as they
do on other file systems. If another file system, application, or kernel
subsystem needs that memory more, it should be available for it to claim.

- -Jeff

- --
Jeff Mahoney
SUSE Labs
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Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org

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Re: [PATCH 4/4] reiserfs: on-demand bitmap loading

[Hans Reiser]

Jeff Mahoney wrote:

> Hans Reiser wrote:
>
> >Are you saying that you allow bitmaps to be unloaded?  If yes, how about
> >making that a separate option, and not the default?
>
>
> They're released, yes. Whether or not they're unloaded is up to the rest
> of the system, vm pressure, etc to determine. This isn't any different
> than the patch I posted before, which you ultimately approved in
> September.
>
> If the bitmaps are to be pinned at all, I'd prefer to make *that* the
> option. ReiserFS's behavior with respect to bitmaps is inconsistent with
> every other Linux file system. I'd prefer to make the dynamic bitmaps
> the default, and if you really must, add an option to continue to pin
> them.
>
> The fact remains that the bitmap blocks are infrequently accessed in
> comparison with other bits of metadata that we don't pin. They're not
> accessed at all in a read-only environment, and barely accessed in a
> light-write workload. If the bitmaps are truly in demand for heavy
> writing, the caches should keep those blocks in memory, the same as they
> do on other file systems. If another file system, application, or kernel
> subsystem needs that memory more, it should be available for it to claim.

Ok.

>
> -Jeff
>
> --
> Jeff Mahoney
> SUSE Labs

[PATCH 4/4] reiserfs: on-demand bitmap loading

[Jeff Mahoney]

 This is the patch the three previous ones have been leading up to.

 It changes the behavior of ReiserFS from loading and caching all the bitmaps
 as special, to treating the bitmaps like any other bit of metadata and just
 letting the system-wide caches figure out what to hang on to.

 Buffer heads are allocated on the fly, so there is no need to retain pointers
 to all of them. The caching of the metadata occurs when the data is read
 and updated, and is considered invalid and uncached until then.

 fs/reiserfs/bitmap.c           |   76 ++++++++++++++++++++---------------------
 fs/reiserfs/resize.c           |   24 +++++++++---
 fs/reiserfs/super.c            |   25 -------------
 include/linux/reiserfs_fs_sb.h |    1 
 4 files changed, 56 insertions(+), 70 deletions(-)

Signed-off-by: Jeff Mahoney <jeffm@suse.com>

diff -ruNpX ../dontdiff linux-2.6.15.orig.staging1/fs/reiserfs/bitmap.c linux-2.6.15.orig.staging2/fs/reiserfs/bitmap.c
--- linux-2.6.15.orig.staging1/fs/reiserfs/bitmap.c	2006-01-16 16:53:33.626628760 -0500
+++ linux-2.6.15.orig.staging2/fs/reiserfs/bitmap.c	2006-01-16 16:53:33.634627544 -0500
@@ -101,8 +101,9 @@ int is_reusable(struct super_block *s, b
 		return 0;
 	}
 
-	bh = SB_AP_BITMAP(s)[i].bh;
-	get_bh(bh);
+	bh = reiserfs_read_bitmap_block(s, bmap);
+	if (bh == NULL)
+		return 0;
 
 	if ((bit_value == 0 && reiserfs_test_le_bit(j, bh->b_data)) ||
 	    (bit_value == 1 && reiserfs_test_le_bit(j, bh->b_data) == 0)) {
@@ -175,13 +176,10 @@ static int scan_bitmap_block(struct reis
 				 bmap_n);
 		return 0;
 	}
-	bh = bi->bh;
-	get_bh(bh);
 
-	if (buffer_locked(bi->bh)) {
-		PROC_INFO_INC(s, scan_bitmap.wait);
-		__wait_on_buffer(bh);
-	}
+	bh = reiserfs_read_bitmap_block(s, bmap_n);
+	if (bh == NULL)
+		return 0;
 
 	while (1) {
 		if (bi->free_count < min) {
@@ -286,9 +284,20 @@ static int bmap_hash_id(struct super_blo
  */
 static inline int block_group_used(struct super_block *s, u32 id)
 {
-	int bm;
-	bm = bmap_hash_id(s, id);
-	if (SB_AP_BITMAP(s)[bm].free_count > ((s->s_blocksize << 3) * 60 / 100)) {
+	int bm = bmap_hash_id(s, id);
+	struct reiserfs_bitmap_info *info = &SB_AP_BITMAP(s)[bm];
+
+	/* If we don't have cached information on this bitmap block, we're
+	 * going to have to load it later anyway. Loading it here allows us
+	 * to make a better decision. This favors long-term performace gain
+	 * with a better on-disk layout vs. a short term gain of skipping the
+	 * read and potentially having a bad placement. */
+	if (info->first_zero_hint == 0) {
+		struct buffer_head *bh = reiserfs_read_bitmap_block(s, bm);
+		brelse(bh);
+	}
+
+	if (info->free_count > ((s->s_blocksize << 3) * 60 / 100)) {
 		return 0;
 	}
 	return 1;
@@ -414,8 +423,9 @@ static void _reiserfs_free_block(struct 
 		return;
 	}
 
-	bmbh = apbi[nr].bh;
-	get_bh(bmbh);
+	bmbh = reiserfs_read_bitmap_block(s, nr);
+	if (!bmbh)
+		return;
 
 	reiserfs_prepare_for_journal(s, bmbh, 1);
 
@@ -1319,6 +1329,7 @@ struct buffer_head *reiserfs_read_bitmap
                                                unsigned int bitmap)
 {
 	unsigned int block = (sb->s_blocksize << 3) * bitmap;
+	struct reiserfs_bitmap_info *info = SB_AP_BITMAP(sb) + bitmap;
 	struct buffer_head *bh;
 
 	/* Way old format filesystems had the bitmaps packed up front.
@@ -1326,9 +1337,20 @@ struct buffer_head *reiserfs_read_bitmap
 	if (test_bit(REISERFS_OLD_FORMAT, &(REISERFS_SB(sb)->s_properties)))
 		block = REISERFS_SB(sb)->s_sbh->b_blocknr + 1 + bitmap;
 
-	bh = sb_getblk(sb, block);
-	if (!buffer_uptodate(bh))
-		ll_rw_block(READ, 1, &bh);
+	bh = sb_bread(sb, block);
+	if (bh == NULL)
+		reiserfs_warning(sb, "sh-2029: reiserfs read_bitmaps: "
+				 "bitmap block (#%lu) reading failed",
+				 bh->b_blocknr);
+	else {
+		if (buffer_locked(bh)) {
+			PROC_INFO_INC(s, scan_bitmap.wait);
+			__wait_on_buffer(bh);
+		}
+		
+		if (info->first_zero_hint == 0)
+			reiserfs_cache_bitmap_metadata(sb, bh, info);
+	}
 
 	return bh;
 }
@@ -1336,7 +1358,6 @@ struct buffer_head *reiserfs_read_bitmap
 int reiserfs_init_bitmap_cache(struct super_block *sb)
 {
 	struct reiserfs_bitmap_info *bitmap;
-	int i;
 
 	bitmap = vmalloc(sizeof (*bitmap) * SB_BMAP_NR(sb));
 	if (bitmap == NULL)
@@ -1344,27 +1365,6 @@ int reiserfs_init_bitmap_cache(struct su
 
 	memset(bitmap, 0, sizeof (*bitmap) * SB_BMAP_NR(sb));
 
-	for (i = 0; i < SB_BMAP_NR(sb); i++)
-		bitmap[i].bh = reiserfs_read_bitmap_block(sb, i);
-
-	/* make sure we have them all */
-	for (i = 0; i < SB_BMAP_NR(sb); i++) {
-		wait_on_buffer(bitmap[i].bh);
-		if (!buffer_uptodate(bitmap[i].bh)) {
-			reiserfs_warning(sb, "sh-2029: reiserfs read_bitmaps: "
-					 "bitmap block (#%lu) reading failed",
-					 bitmap[i].bh->b_blocknr);
-			for (i = 0; i < SB_BMAP_NR(sb); i++)
-				brelse(bitmap[i].bh);
-			vfree(bitmap);
-			return 1;
-		}
-	}
-
-	/* Cache the info on the bitmaps before we get rolling */
-	for (i = 0; i < SB_BMAP_NR(sb); i++)
-		reiserfs_cache_bitmap_metadata(sb, bitmap[i].bh, &bitmap[i]);
-
 	SB_AP_BITMAP(sb) = bitmap;
 
 	return 0;
diff -ruNpX ../dontdiff linux-2.6.15.orig.staging1/fs/reiserfs/resize.c linux-2.6.15.orig.staging2/fs/reiserfs/resize.c
--- linux-2.6.15.orig.staging1/fs/reiserfs/resize.c	2006-01-16 16:53:33.626628760 -0500
+++ linux-2.6.15.orig.staging2/fs/reiserfs/resize.c	2006-01-16 16:53:33.636627240 -0500
@@ -128,8 +128,9 @@ int reiserfs_resize(struct super_block *
 		 * transaction begins, and the new bitmaps don't matter if the
 		 * transaction fails. */
 		for (i = bmap_nr; i < bmap_nr_new; i++) {
-			bh = sb_getblk(s, i * s->s_blocksize * 8);
-			get_bh(bh);
+			/* don't use read_bitmap_block since it will cache
+			 * the uninitialized bitmap */
+			bh = sb_bread(s, i * s->s_blocksize * 8);
 			memset(bh->b_data, 0, sb_blocksize(sb));
 			reiserfs_test_and_set_le_bit(0, bh->b_data);
 			reiserfs_cache_bitmap_metadata(s, bh, bitmap + i);
@@ -140,7 +141,6 @@ int reiserfs_resize(struct super_block *
 			// update bitmap_info stuff
 			bitmap[i].first_zero_hint = 1;
 			bitmap[i].free_count = sb_blocksize(sb) * 8 - 1;
-			bitmap[i].bh = bh;
 			brelse(bh);
 		}
 		/* free old bitmap blocks array */
@@ -157,8 +157,13 @@ int reiserfs_resize(struct super_block *
 
 	/* Extend old last bitmap block - new blocks have been made available */
 	info = SB_AP_BITMAP(s) + bmap_nr - 1;
-	bh = info->bh;
-	get_bh(bh);
+	bh = reiserfs_read_bitmap_block(s, bmap_nr - 1);
+	if (!bh) {
+		int jerr = journal_end(&th, s, 10);
+		if (jerr)
+			return jerr;
+		return -EIO;
+	}
 
 	reiserfs_prepare_for_journal(s, bh, 1);
 	for (i = block_r; i < s->s_blocksize * 8; i++)
@@ -172,8 +177,13 @@ int reiserfs_resize(struct super_block *
 
 	/* Correct new last bitmap block - It may not be full */
 	info = SB_AP_BITMAP(s) + bmap_nr_new - 1;
-	bh = info->bh;
-	get_bh(bh);
+	bh = reiserfs_read_bitmap_block(s, bmap_nr_new - 1);
+	if (!bh) {
+		int jerr = journal_end(&th, s, 10);
+		if (jerr)
+			return jerr;
+		return -EIO;
+	}
 
 	reiserfs_prepare_for_journal(s, bh, 1);
 	for (i = block_r_new; i < s->s_blocksize * 8; i++)
diff -ruNpX ../dontdiff linux-2.6.15.orig.staging1/fs/reiserfs/super.c linux-2.6.15.orig.staging2/fs/reiserfs/super.c
--- linux-2.6.15.orig.staging1/fs/reiserfs/super.c	2006-01-16 16:53:33.628628456 -0500
+++ linux-2.6.15.orig.staging2/fs/reiserfs/super.c	2006-01-16 16:53:33.637627088 -0500
@@ -433,7 +433,6 @@ int remove_save_link(struct inode *inode
 
 static void reiserfs_put_super(struct super_block *s)
 {
-	int i;
 	struct reiserfs_transaction_handle th;
 	th.t_trans_id = 0;
 
@@ -463,9 +462,6 @@ static void reiserfs_put_super(struct su
 	 */
 	journal_release(&th, s);
 
-	for (i = 0; i < SB_BMAP_NR(s); i++)
-		brelse(SB_AP_BITMAP(s)[i].bh);
-
 	vfree(SB_AP_BITMAP(s));
 
 	brelse(SB_BUFFER_WITH_SB(s));
@@ -1365,7 +1361,6 @@ static int read_super_block(struct super
 /* after journal replay, reread all bitmap and super blocks */
 static int reread_meta_blocks(struct super_block *s)
 {
-	int i;
 	ll_rw_block(READ, 1, &(SB_BUFFER_WITH_SB(s)));
 	wait_on_buffer(SB_BUFFER_WITH_SB(s));
 	if (!buffer_uptodate(SB_BUFFER_WITH_SB(s))) {
@@ -1374,20 +1369,7 @@ static int reread_meta_blocks(struct sup
 		return 1;
 	}
 
-	for (i = 0; i < SB_BMAP_NR(s); i++) {
-		ll_rw_block(READ, 1, &(SB_AP_BITMAP(s)[i].bh));
-		wait_on_buffer(SB_AP_BITMAP(s)[i].bh);
-		if (!buffer_uptodate(SB_AP_BITMAP(s)[i].bh)) {
-			reiserfs_warning(s,
-					 "reread_meta_blocks, error reading bitmap block number %d at %llu",
-					 i,
-					 (unsigned long long)SB_AP_BITMAP(s)[i].
-					 bh->b_blocknr);
-			return 1;
-		}
-	}
 	return 0;
-
 }
 
 /////////////////////////////////////////////////////
@@ -1814,13 +1796,8 @@ static int reiserfs_fill_super(struct su
 	if (jinit_done) {	/* kill the commit thread, free journal ram */
 		journal_release_error(NULL, s);
 	}
-	if (SB_DISK_SUPER_BLOCK(s)) {
-		for (j = 0; j < SB_BMAP_NR(s); j++) {
-			if (SB_AP_BITMAP(s))
-				brelse(SB_AP_BITMAP(s)[j].bh);
-		}
+	if (SB_DISK_SUPER_BLOCK(s))
 		vfree(SB_AP_BITMAP(s));
-	}
 	if (SB_BUFFER_WITH_SB(s))
 		brelse(SB_BUFFER_WITH_SB(s));
 #ifdef CONFIG_QUOTA
diff -ruNpX ../dontdiff linux-2.6.15.orig.staging1/include/linux/reiserfs_fs_sb.h linux-2.6.15.orig.staging2/include/linux/reiserfs_fs_sb.h
--- linux-2.6.15.orig.staging1/include/linux/reiserfs_fs_sb.h	2006-01-16 16:53:29.453263208 -0500
+++ linux-2.6.15.orig.staging2/include/linux/reiserfs_fs_sb.h	2006-01-16 16:53:33.638626936 -0500
@@ -267,7 +267,6 @@ struct reiserfs_bitmap_info {
 	// FIXME: Won't work with block sizes > 8K
 	__u16 first_zero_hint;
 	__u16 free_count;
-	struct buffer_head *bh;	/* the actual bitmap */
 };
 
 struct proc_dir_entry;
-- 
Jeff Mahoney
SuSE Labs