The patch titled
Subject: ext4: use memweight()
has been added to the -mm tree. Its filename is
ext4-use-memweight.patch
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From: Akinobu Mita <akinobu.mita@xxxxxxxxx>
Subject: ext4: use memweight()
Convert ext4_count_free() to use memweight() instead of table lookup based
counting clear bits implementation. This change only affects the code
segments enabled by EXT4FS_DEBUG.
Note that this memweight() call can't be replaced with a single
bitmap_weight() call, although the pointer to the memory area is aligned
to long-word boundary. Because the size of the memory area may not be a
multiple of BITS_PER_LONG, then it returns wrong value on big-endian
architecture.
This also includes the following change.
- Remove unnecessary map == NULL check in ext4_count_free() which
always takes non-null pointer as the memory area.
Signed-off-by: Akinobu Mita <akinobu.mita@xxxxxxxxx>
Cc: "Theodore Ts'o" <tytso@xxxxxxx>
Cc: Andreas Dilger <adilger.kernel@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/ext4/bitmap.c | 11 +----------
1 file changed, 1 insertion(+), 10 deletions(-)
diff -puN fs/ext4/bitmap.c~ext4-use-memweight fs/ext4/bitmap.c
--- a/fs/ext4/bitmap.c~ext4-use-memweight
+++ a/fs/ext4/bitmap.c
@@ -13,18 +13,9 @@
#ifdef EXT4FS_DEBUG
-static const int nibblemap[] = {4, 3, 3, 2, 3, 2, 2, 1, 3, 2, 2, 1, 2, 1, 1, 0};
-
unsigned int ext4_count_free(struct buffer_head *map, unsigned int numchars)
{
- unsigned int i, sum = 0;
-
- if (!map)
- return 0;
- for (i = 0; i < numchars; i++)
- sum += nibblemap[map->b_data[i] & 0xf] +
- nibblemap[(map->b_data[i] >> 4) & 0xf];
- return sum;
+ return numchars * BITS_PER_BYTE - memweight(map->b_data, numchars);
}
#endif /* EXT4FS_DEBUG */
_
Subject: Subject: ext4: use memweight()
Patches currently in -mm which might be from akinobu.mita@xxxxxxxxx are
linux-next.patch
ocfs2-use-find_last_bit.patch
ocfs2-use-bitmap_weight.patch
string-introduce-memweight.patch
string-introduce-memweight-fix.patch
qnx4fs-use-memweight.patch
dm-use-memweight.patch
affs-use-memweight.patch
video-uvc-use-memweight.patch
ocfs2-use-memweight.patch
ext2-use-memweight.patch
ext3-use-memweight.patch
ext4-use-memweight.patch
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