[PATCH] reiserfs: on-demand bitmap loading

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.

I needed to remove the vs-4040 check for performing a duplicate operation on a
particular bit.  The reason is that while the other sites for working with
bitmaps are allowed to schedule, is_reusable() is called from do_balance(),
which will panic if a schedule occurs in certain places.

The benefit of on-demand bitmaps clearly outweighs a sanity check that depends
on a compile-time option that is discouraged.

[akpm@osdl.org: warning fix]
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Cc: <reiserfs-dev@namesys.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/reiserfs/bitmap.c

@@ -60,7 +60,6 @@ static inline void get_bit_address(struct super_block *s,
 int is_reusable(struct super_block *s, b_blocknr_t block, int bit_value)
 {
 	int bmap, offset;
-	struct buffer_head *bh;
 
 	if (block == 0 || block >= SB_BLOCK_COUNT(s)) {
 		reiserfs_warning(s,
@@ -98,22 +97,6 @@ int is_reusable(struct super_block *s, b_blocknr_t block, int bit_value)
 		return 0;
 	}
 
-	bh = SB_AP_BITMAP(s)[bmap].bh;
-	get_bh(bh);
-
-	if ((bit_value == 0 && reiserfs_test_le_bit(offset, bh->b_data)) ||
-	    (bit_value == 1 && reiserfs_test_le_bit(offset, bh->b_data) == 0)) {
-		reiserfs_warning(s,
-				 "vs-4040: is_reusable: corresponding bit of block %lu does not "
-				 "match required value (bmap==%d, offset==%d) test_bit==%d",
-				 block, bmap, offset,
-				 reiserfs_test_le_bit(offset, bh->b_data));
-
-		brelse(bh);
-		return 0;
-	}
-	brelse(bh);
-
 	if (bit_value == 0 && block == SB_ROOT_BLOCK(s)) {
 		reiserfs_warning(s,
 				 "vs-4050: is_reusable: this is root block (%u), "
@@ -173,13 +156,10 @@ static int scan_bitmap_block(struct reiserfs_transaction_handle *th,
 				 bmap_n);
 		return 0;
 	}
-	bh = bi->bh;
-	get_bh(bh);
 
-	if (buffer_locked(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) {
 	      cont:
@@ -285,9 +265,20 @@ static int bmap_hash_id(struct super_block *s, u32 id)
  */
 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;
@@ -413,8 +404,9 @@ static void _reiserfs_free_block(struct reiserfs_transaction_handle *th,
 		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);
 
@@ -1320,6 +1312,7 @@ struct buffer_head *reiserfs_read_bitmap_block(struct super_block *sb,
                                                unsigned int bitmap)
 {
 	b_blocknr_t 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.
@@ -1330,46 +1323,44 @@ struct buffer_head *reiserfs_read_bitmap_block(struct super_block *sb,
 	else if (bitmap == 0)
 		block = (REISERFS_DISK_OFFSET_IN_BYTES >> sb->s_blocksize_bits) + 1;
 
-	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: %s: bitmap block (#%lu) "
+		                 "reading failed", __FUNCTION__, bh->b_blocknr);
+	else {
+		if (buffer_locked(bh)) {
+			PROC_INFO_INC(sb, scan_bitmap.wait);
+			__wait_on_buffer(bh);
+		}
+		BUG_ON(!buffer_uptodate(bh));
+		BUG_ON(atomic_read(&bh->b_count) == 0);
+
+		if (info->first_zero_hint == 0)
+			reiserfs_cache_bitmap_metadata(sb, bh, info);
+	}
 
 	return bh;
 }
 
 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)
 		return -ENOMEM;
 
 	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: %s: "
-					 "bitmap block (#%lu) reading failed",
-			                 __FUNCTION__, bitmap[i].bh->b_blocknr);
-			for (i = 0; i < SB_BMAP_NR(sb); i++)
-				brelse(bitmap[i].bh);
-			vfree(bitmap);
-			return -EIO;
-		}
-	}
-
-	/* 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;
 }
+
+void reiserfs_free_bitmap_cache(struct super_block *sb)
+{
+	if (SB_AP_BITMAP(sb)) {
+		vfree(SB_AP_BITMAP(sb));
+		SB_AP_BITMAP(sb) = NULL;
+	}
+}

fs/reiserfs/resize.c

@@ -128,8 +128,9 @@ int reiserfs_resize(struct super_block *s, unsigned long block_count_new)
 		 * 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 *s, unsigned long block_count_new)
 			// 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 *s, unsigned long block_count_new)
 
 	/* 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 *s, unsigned long block_count_new)
 
 	/* 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++)

fs/reiserfs/super.c

@@ -432,7 +432,6 @@ int remove_save_link(struct inode *inode, int truncate)
 
 static void reiserfs_put_super(struct super_block *s)
 {
-	int i;
 	struct reiserfs_transaction_handle th;
 	th.t_trans_id = 0;
 
@@ -462,10 +461,7 @@ static void reiserfs_put_super(struct super_block *s)
 	 */
 	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));
+	reiserfs_free_bitmap_cache(s);
 
 	brelse(SB_BUFFER_WITH_SB(s));
 
@@ -1344,7 +1340,6 @@ static int read_super_block(struct super_block *s, int offset)
 /* 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))) {
@@ -1353,20 +1348,7 @@ static int reread_meta_blocks(struct super_block *s)
 		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;
-
 }
 
 /////////////////////////////////////////////////////
@@ -1547,7 +1529,6 @@ static int function2code(hashf_t func)
 static int reiserfs_fill_super(struct super_block *s, void *data, int silent)
 {
 	struct inode *root_inode;
-	int j;
 	struct reiserfs_transaction_handle th;
 	int old_format = 0;
 	unsigned long blocks;
@@ -1793,19 +1774,17 @@ static int reiserfs_fill_super(struct super_block *s, void *data, int silent)
 	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);
-		}
-		vfree(SB_AP_BITMAP(s));
-	}
+
+	reiserfs_free_bitmap_cache(s);
 	if (SB_BUFFER_WITH_SB(s))
 		brelse(SB_BUFFER_WITH_SB(s));
 #ifdef CONFIG_QUOTA
-	for (j = 0; j < MAXQUOTAS; j++) {
-		kfree(sbi->s_qf_names[j]);
-		sbi->s_qf_names[j] = NULL;
+	{
+		int j;
+		for (j = 0; j < MAXQUOTAS; j++) {
+			kfree(sbi->s_qf_names[j]);
+			sbi->s_qf_names[j] = NULL;
+		}
 	}
 #endif
 	kfree(sbi);

include/linux/reiserfs_fs_sb.h

@@ -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;