diff options
| author | Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> | 2009-02-17 10:58:33 -0500 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2009-02-20 14:37:10 -0800 |
| commit | a07daf9af79b827bff630f6f9be4729de3a54eea (patch) | |
| tree | 761f63a0c1db7ad8d350991a78b81b00c9673386 | |
| parent | 919a7cd36ae67ccc0a5e44b7a44a96065b11aa01 (diff) | |
ext4: Fix race between read_block_bitmap() and mark_diskspace_used()
(cherry picked from commit e8134b27e351e813414da3b95aa8eac6d3908088)
We need to make sure we update the block bitmap and clear
EXT4_BG_BLOCK_UNINIT flag with sb_bgl_lock held, since
ext4_read_block_bitmap() looks at EXT4_BG_BLOCK_UNINIT to decide
whether to initialize the block bitmap each time it is called
(introduced by commit c806e68f), and this can race with block
allocations in ext4_mb_mark_diskspace_used().
ext4_read_block_bitmap does:
spin_lock(sb_bgl_lock(EXT4_SB(sb), block_group));
if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
ext4_init_block_bitmap(sb, bh, block_group, desc);
Now on the block allocation side we do
mb_set_bits(sb_bgl_lock(sbi, ac->ac_b_ex.fe_group), bitmap_bh->b_data,
ac->ac_b_ex.fe_start, ac->ac_b_ex.fe_len);
....
spin_lock(sb_bgl_lock(sbi, ac->ac_b_ex.fe_group));
if (gdp->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
gdp->bg_flags &= cpu_to_le16(~EXT4_BG_BLOCK_UNINIT);
ie on allocation we update the bitmap then we take the sb_bgl_lock
and clear the EXT4_BG_BLOCK_UNINIT flag. What can happen is a
parallel ext4_read_block_bitmap can zero out the bitmap in between
the above mb_set_bits and spin_lock(sb_bg_lock..)
The race results in below user visible errors
EXT4-fs error (device sdb1): ext4_mb_release_inode_pa: free 100, pa_free 105
EXT4-fs error (device sdb1): mb_free_blocks: double-free of inode 0's block ..
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
| -rw-r--r-- | fs/ext4/mballoc.c | 15 |
1 files changed, 10 insertions, 5 deletions
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index d82b86ec31c..f96b18eb11b 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -1070,7 +1070,10 @@ static void mb_clear_bits(spinlock_t *lock, void *bm, int cur, int len) cur += 32; continue; } - mb_clear_bit_atomic(lock, cur, bm); + if (lock) + mb_clear_bit_atomic(lock, cur, bm); + else + mb_clear_bit(cur, bm); cur++; } } @@ -1088,7 +1091,10 @@ static void mb_set_bits(spinlock_t *lock, void *bm, int cur, int len) cur += 32; continue; } - mb_set_bit_atomic(lock, cur, bm); + if (lock) + mb_set_bit_atomic(lock, cur, bm); + else + mb_set_bit(cur, bm); cur++; } } @@ -3143,10 +3149,9 @@ ext4_mb_mark_diskspace_used(struct ext4_allocation_context *ac, } } #endif - mb_set_bits(sb_bgl_lock(sbi, ac->ac_b_ex.fe_group), bitmap_bh->b_data, - ac->ac_b_ex.fe_start, ac->ac_b_ex.fe_len); - spin_lock(sb_bgl_lock(sbi, ac->ac_b_ex.fe_group)); + mb_set_bits(NULL, bitmap_bh->b_data, + ac->ac_b_ex.fe_start, ac->ac_b_ex.fe_len); if (gdp->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) { gdp->bg_flags &= cpu_to_le16(~EXT4_BG_BLOCK_UNINIT); gdp->bg_free_blocks_count = |