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fat: mmu_private race fix

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mmu_private is 64bits value, hence it's not atomic to update.

So, the access rule for mmu_private is we must hold ->i_mutex.  But,
fat_get_block() path doesn't follow the rule on non-allocation path.

This fixes by using i_size instead if non-allocation path.

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>
This commit is contained in:
OGAWA Hirofumi
2008-11-06 12:53:57 -08:00
committed by Linus Torvalds
parent 0e75f5da06
commit 2bdf67eb16
4 changed files with 25 additions and 10 deletions
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23
fs/fat/cache.c
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@@ -293,10 +293,12 @@ static int fat_bmap_cluster(struct inode *inode, int cluster)
}
int fat_bmap(struct inode *inode, sector_t sector, sector_t *phys,
unsigned long *mapped_blocks)
unsigned long *mapped_blocks, int create)
{
struct super_block *sb = inode->i_sb;
struct msdos_sb_info *sbi = MSDOS_SB(sb);
const unsigned long blocksize = sb->s_blocksize;
const unsigned char blocksize_bits = sb->s_blocksize_bits;
sector_t last_block;
int cluster, offset;
@@ -309,10 +311,21 @@ int fat_bmap(struct inode *inode, sector_t sector, sector_t *phys,
}
return 0;
}
last_block = (MSDOS_I(inode)->mmu_private + (sb->s_blocksize - 1))
>> sb->s_blocksize_bits;
if (sector >= last_block)
return 0;
last_block = (i_size_read(inode) + (blocksize - 1)) >> blocksize_bits;
if (sector >= last_block) {
if (!create)
return 0;
/*
* ->mmu_private can access on only allocation path.
* (caller must hold ->i_mutex)
*/
last_block = (MSDOS_I(inode)->mmu_private + (blocksize - 1))
>> blocksize_bits;
if (sector >= last_block)
return 0;
}
cluster = sector >> (sbi->cluster_bits - sb->s_blocksize_bits);
offset = sector & (sbi->sec_per_clus - 1);