diff options
| author | OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> | 2008-01-08 15:32:41 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2008-01-08 16:10:35 -0800 |
| commit | 9f966be8996f2829406324c68e4c67c2d64d864b (patch) | |
| tree | 40b2e1f12834498f1e7d8240fe7f6f3dbaf0dce2 /fs/fat | |
| parent | d52df2e2ea2d881b1439bbdec7f67c27e0f47941 (diff) | |
fat: optimize fat_count_free_clusters()
On large partition, scanning the free clusters is very slow if users
doesn't use "usefree" option.
For optimizing it, this patch uses sb_breadahead() to read of FAT
sectors. On some user's 15GB partition, this patch improved it very
much (1min => 600ms).
The following is the result of 2GB partition on my machine.
without patch:
root@devron (/)# time df -h > /dev/null
real 0m1.202s
user 0m0.000s
sys 0m0.440s
with patch:
root@devron (/)# time df -h > /dev/null
real 0m0.378s
user 0m0.012s
sys 0m0.168s
Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/fat')
| -rw-r--r-- | fs/fat/fatent.c | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/fs/fat/fatent.c b/fs/fat/fatent.c index 2c1b73fb82a..5fb366992b7 100644 --- a/fs/fat/fatent.c +++ b/fs/fat/fatent.c @@ -590,21 +590,49 @@ error: EXPORT_SYMBOL_GPL(fat_free_clusters); +/* 128kb is the whole sectors for FAT12 and FAT16 */ +#define FAT_READA_SIZE (128 * 1024) + +static void fat_ent_reada(struct super_block *sb, struct fat_entry *fatent, + unsigned long reada_blocks) +{ + struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops; + sector_t blocknr; + int i, offset; + + ops->ent_blocknr(sb, fatent->entry, &offset, &blocknr); + + for (i = 0; i < reada_blocks; i++) + sb_breadahead(sb, blocknr + i); +} + int fat_count_free_clusters(struct super_block *sb) { struct msdos_sb_info *sbi = MSDOS_SB(sb); struct fatent_operations *ops = sbi->fatent_ops; struct fat_entry fatent; + unsigned long reada_blocks, reada_mask, cur_block; int err = 0, free; lock_fat(sbi); if (sbi->free_clusters != -1) goto out; + reada_blocks = FAT_READA_SIZE >> sb->s_blocksize_bits; + reada_mask = reada_blocks - 1; + cur_block = 0; + free = 0; fatent_init(&fatent); fatent_set_entry(&fatent, FAT_START_ENT); while (fatent.entry < sbi->max_cluster) { + /* readahead of fat blocks */ + if ((cur_block & reada_mask) == 0) { + unsigned long rest = sbi->fat_length - cur_block; + fat_ent_reada(sb, &fatent, min(reada_blocks, rest)); + } + cur_block++; + err = fat_ent_read_block(sb, &fatent); if (err) goto out; |