diff options
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 2c1b73fb82ae..5fb366992b73 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; |