xfs: avoid overflows in i_delayed_blks due to numerous cow reservations
PATCH 1/1 xfs: avoid overflows in i_delayed_blks due to numerous cow reservations
From: Darrick J. Wong <[email protected]>
Prior to the arrival of copy on write, i_delayed_blks tracked the number of blocks that had been reserved for delayed allocations. Though the counter was 32-bits in size, this was enough because writeback would generally start flushing files well before we hit 2^32 blocks of dirty data.
However, now that we're using it to track CoW reservations as well, it's possible to create so many of those reservations that we overflow the counter. This is kind of an extreme case (it requires ~16T of COW reservations) but we ought to avoid this trivial overflow. A userspace visible effect is that stat i_blocks returns incorrect values.
Change the field to xfs_filblks_t, which should suffice to fix the problem. There already was a 4-byte hole in struct xfs_inode, so we get this for free.
--- fs/xfs/xfs_inode.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
fs/xfs/xfs_inode.h +1 -1
@@ -48,7 +48,7 @@ typedef struct xfs_inode {spinlock_t i_flags_lock;/* inode i_flags lock */ /* Miscellaneous state. */ unsigned long i_flags;/* see defined flags below */ -unsigned int i_delayed_blks;/* count of delay alloc blks */ +xfs_filblks_t i_delayed_blks;/* count of delay alloc blks */ struct xfs_icdinode i_d;/* most of ondisk inode */
Quoted 14 lines · Darrick J. Wong
From: Darrick J. Wong <[email protected]>
Prior to the arrival of copy on write,
i_delayed_blkstracked the number of blocks that had been reserved for delayed allocations. Though the counter was 32-bits in size, this was enough because writeback would generally start flushing files well before we hit 2^32 blocks of dirty data.However, now that we're using it to track CoW reservations as well, it's possible to create so many of those reservations that we overflow the counter. This is kind of an extreme case (it requires ~16T of COW reservations) but we ought to avoid this trivial overflow. A userspace visible effect is that stat
i_blocksreturns incorrect values.
Quoted 5 lines
Change the field to
xfs_filblks_t, which should suffice to fix the problem. There already was a 4-byte hole in structxfs_inode, so we get this for free.Signed-off-by Darrick J. Wong <[email protected]>
I think delblks in xfs_qm_vop_chown_reserve() needs to be bumped up too then, no?
(and, uh, does it then need to be chased through xfs_trans_reserve_quota_bydquot, xfs_trans_dqresv etc?)
-Eric
Quoted 18 lines
--- fs/xfs/xfs_inode.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)fs/xfs/xfs_inode.h +1
-2@@ -48,7 +48,7 @@ typedef struct xfs_inode {spinlock_t i_flags_lock;/* inode i_flags lock */ /* Miscellaneous state. */ unsigned long i_flags;/* see defined flags below */ -unsigned int i_delayed_blks;/* count of delay alloc blks */ +xfs_filblks_t i_delayed_blks;/* count of delay alloc blks */ struct xfs_icdinode i_d;/* most of ondisk inode */ --