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xfs: fix filesystsem freeze race in xfs_trans_alloc

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As pointed out by Jan xfs_trans_alloc can race with a concurrent filesystem
freeze when it sleeps during the memory allocation.  Fix this by moving the
wait_for_freeze call after the memory allocation.  This means moving the
freeze into the low-level _xfs_trans_alloc helper, which thus grows a new
argument.  Also fix up some comments in that area while at it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Alex Elder <aelder@sgi.com>
Reviewed-by: Dave Chinner <david@fromorbit.com>
This commit is contained in:
Christoph Hellwig
2011-07-08 14:34:42 +02:00
parent 33b8f7c247
commit 7a249cf83d
5 changed files with 27 additions and 29 deletions
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27
fs/xfs/xfs_trans.c
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@@ -566,31 +566,24 @@ xfs_trans_init(
/*
* This routine is called to allocate a transaction structure.
*
* The type parameter indicates the type of the transaction. These
* are enumerated in xfs_trans.h.
*
* Dynamically allocate the transaction structure from the transaction
* zone, initialize it, and return it to the caller.
*/
xfs_trans_t *
xfs_trans_alloc(
xfs_mount_t *mp,
uint type)
{
xfs_wait_for_freeze(mp, SB_FREEZE_TRANS);
return _xfs_trans_alloc(mp, type, KM_SLEEP);
}
xfs_trans_t *
struct xfs_trans *
_xfs_trans_alloc(
xfs_mount_t *mp,
uint type,
uint memflags)
struct xfs_mount *mp,
uint type,
uint memflags,
bool wait_for_freeze)
{
xfs_trans_t *tp;
struct xfs_trans *tp;
atomic_inc(&mp->m_active_trans);
if (wait_for_freeze)
xfs_wait_for_freeze(mp, SB_FREEZE_TRANS);
tp = kmem_zone_zalloc(xfs_trans_zone, memflags);
tp->t_magic = XFS_TRANS_MAGIC;
tp->t_type = type;