[patch 6/7] reiserfs: remove first_zero_hint

[Jeff Mahoney <jeffm@suse.com>]

[-- Attachment #1: patches.suse/reiserfs-remove-first-zero-hint.diff --]
[-- Type: text/plain, Size: 4117 bytes --]

 The first_zero_hint metadata caching was never actually used, and it's
 of dubious optimization quality. This patch removes it.

 It doesn't actually shrink the size of the reiserfs_bitmap_info struct,
 since that doesn't work with block sizes larger than 8K. There was a big
 fixme in there, and with all the work lately in allowing block size >
 page size, I might as well kill the fixme as well.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
---
 fs/reiserfs/bitmap.c           |   27 +++++++++++----------------
 fs/reiserfs/resize.c           |    6 ------
 include/linux/reiserfs_fs_sb.h |    4 +---
 3 files changed, 12 insertions(+), 25 deletions(-)

--- a/fs/reiserfs/bitmap.c	2007-10-16 18:55:51.029160630 -0400
+++ b/fs/reiserfs/bitmap.c	2007-10-16 18:55:56.205787201 -0400
@@ -273,7 +273,7 @@ static inline int block_group_used(struc
 	 * 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) {
+	if (info->free_count == UINT_MAX) {
 		struct buffer_head *bh = reiserfs_read_bitmap_block(s, bm);
 		brelse(bh);
 	}
@@ -1271,27 +1271,22 @@ void reiserfs_cache_bitmap_metadata(stru
 {
 	unsigned long *cur = (unsigned long *)(bh->b_data + bh->b_size);
 
-	info->first_zero_hint = 1 << (sb->s_blocksize_bits + 3);
+	/* The first bit must ALWAYS be 1 */
+	BUG_ON (!reiserfs_test_le_bit(0, (unsigned long)bh->b_data))
+
+	info->free_count = 0;
 
 	while (--cur >= (unsigned long *)bh->b_data) {
-		int base = ((char *)cur - bh->b_data) << 3;
+		int i;
 
 		/* 0 and ~0 are special, we can optimize for them */
-		if (*cur == 0) {
-			info->first_zero_hint = base;
+		if (*cur == 0)
 			info->free_count += BITS_PER_LONG;
-		} else if (*cur != ~0L) {       /* A mix, investigate */
-			int b;
-			for (b = BITS_PER_LONG - 1; b >= 0; b--) {
-				if (!reiserfs_test_le_bit(b, cur)) {
-					info->first_zero_hint = base + b;
+		else if (*cur != ~0L)	/* A mix, investigate */
+			for (i = BITS_PER_LONG - 1; i >= 0; i--)
+				if (!reiserfs_test_le_bit(i, cur))
 					info->free_count++;
-				}
-			}
-		}
 	}
-	/* The first bit must ALWAYS be 1 */
-	BUG_ON(info->first_zero_hint == 0);
 }
 
 struct buffer_head *reiserfs_read_bitmap_block(struct super_block *sb,
@@ -1321,7 +1316,7 @@ struct buffer_head *reiserfs_read_bitmap
 		BUG_ON(!buffer_uptodate(bh));
 		BUG_ON(atomic_read(&bh->b_count) == 0);
 
-		if (info->first_zero_hint == 0)
+		if (info->free_count == UINT_MAX)
 			reiserfs_cache_bitmap_metadata(sb, bh, info);
 	}
 
--- a/fs/reiserfs/resize.c	2007-10-16 18:55:51.029160630 -0400
+++ b/fs/reiserfs/resize.c	2007-10-16 18:55:56.206787129 -0400
@@ -143,7 +143,6 @@ int reiserfs_resize(struct super_block *
 			mark_buffer_dirty(bh);
 			sync_dirty_buffer(bh);
 			// update bitmap_info stuff
-			bitmap[i].first_zero_hint = 1;
 			bitmap[i].free_count = sb_blocksize(sb) * 8 - 1;
 			brelse(bh);
 		}
@@ -173,8 +172,6 @@ int reiserfs_resize(struct super_block *
 	for (i = block_r; i < s->s_blocksize * 8; i++)
 		reiserfs_test_and_clear_le_bit(i, bh->b_data);
 	info->free_count += s->s_blocksize * 8 - block_r;
-	if (!info->first_zero_hint)
-		info->first_zero_hint = block_r;
 
 	journal_mark_dirty(&th, s, bh);
 	brelse(bh);
@@ -196,9 +193,6 @@ int reiserfs_resize(struct super_block *
 	brelse(bh);
 
 	info->free_count -= s->s_blocksize * 8 - block_r_new;
-	/* Extreme case where last bitmap is the only valid block in itself. */
-	if (!info->free_count)
-		info->first_zero_hint = 0;
 	/* update super */
 	reiserfs_prepare_for_journal(s, SB_BUFFER_WITH_SB(s), 1);
 	free_blocks = SB_FREE_BLOCKS(s);
--- a/include/linux/reiserfs_fs_sb.h	2007-10-16 18:55:51.030160558 -0400
+++ b/include/linux/reiserfs_fs_sb.h	2007-10-16 18:55:53.964948838 -0400
@@ -265,9 +265,7 @@ enum journal_state_bits {
 typedef __u32(*hashf_t) (const signed char *, int);
 
 struct reiserfs_bitmap_info {
-	// FIXME: Won't work with block sizes > 8K
-	__u16 first_zero_hint;
-	__u16 free_count;
+	__u32 free_count;
 };
 
 struct proc_dir_entry;

--