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authorAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>2009-01-05 21:38:26 -0500
committerTheodore Ts'o <tytso@mit.edu>2009-01-05 21:38:26 -0500
commite8134b27e351e813414da3b95aa8eac6d3908088 (patch)
treec2d9939f92cc326b4ecfc3903a489fb753cb344c
parent5d1b1b3f492f8696ea18950a454a141381b0f926 (diff)
ext4: Fix race between read_block_bitmap() and mark_diskspace_used()
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> Cc: stable@kernel.org
-rw-r--r--fs/ext4/mballoc.c15
1 files changed, 10 insertions, 5 deletions
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index cda69632eea..d559a03f3eb 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++;
}
}
@@ -3035,10 +3041,9 @@ 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 =