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xfs: fix filesystsem freeze race in xfs_trans_alloc 

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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2
fs/xfs/xfs_fsops.c
View File

@ -626,7 +626,7 @@ xfs_fs_log_dummy(
xfs_trans_t *tp;
int error;
tp = _xfs_trans_alloc(mp, XFS_TRANS_DUMMY1, KM_SLEEP);
tp = _xfs_trans_alloc(mp, XFS_TRANS_DUMMY1, KM_SLEEP, false);
error = xfs_trans_reserve(tp, 0, mp->m_sb.sb_sectsize + 128, 0, 0,
XFS_DEFAULT_LOG_COUNT);
if (error) {

3
fs/xfs/xfs_iomap.c
View File

@ -688,8 +688,7 @@ xfs_iomap_write_unwritten(
* the same inode that we complete here and might deadlock
* on the iolock.
*/
xfs_wait_for_freeze(mp, SB_FREEZE_TRANS);
tp = _xfs_trans_alloc(mp, XFS_TRANS_STRAT_WRITE, KM_NOFS);
tp = _xfs_trans_alloc(mp, XFS_TRANS_STRAT_WRITE, KM_NOFS, true);
tp->t_flags |= XFS_TRANS_RESERVE;
error = xfs_trans_reserve(tp, resblks,
XFS_WRITE_LOG_RES(mp), 0,

14
fs/xfs/xfs_mount.c
View File

@ -1566,15 +1566,9 @@ xfs_fs_writable(xfs_mount_t *mp)
}
/*
* xfs_log_sbcount
*
* Called either periodically to keep the on disk superblock values
* roughly up to date or from unmount to make sure the values are
* correct on a clean unmount.
*
* Note this code can be called during the process of freezing, so
* we may need to use the transaction allocator which does not not
* block when the transaction subsystem is in its frozen state.
*/
int
xfs_log_sbcount(
@ -1596,7 +1590,13 @@ xfs_log_sbcount(
if (!xfs_sb_version_haslazysbcount(&mp->m_sb))
return 0;
tp = _xfs_trans_alloc(mp, XFS_TRANS_SB_COUNT, KM_SLEEP);
/*
* We can be called during the process of freezing, so make sure
* we go ahead even if the frozen for new transactions. We will
* always use a sync transaction in the freeze path to make sure
* the transaction has completed by the time we return.
*/
tp = _xfs_trans_alloc(mp, XFS_TRANS_SB_COUNT, KM_SLEEP, false);
error = xfs_trans_reserve(tp, 0, mp->m_sb.sb_sectsize + 128, 0, 0,
XFS_DEFAULT_LOG_COUNT);
if (error) {

27
fs/xfs/xfs_trans.c
View File

@ -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;

10
fs/xfs/xfs_trans.h
View File

@ -447,8 +447,14 @@ typedef struct xfs_trans {
/*
* XFS transaction mechanism exported interfaces.
*/
xfs_trans_t *xfs_trans_alloc(struct xfs_mount *, uint);
xfs_trans_t *_xfs_trans_alloc(struct xfs_mount *, uint, uint);
xfs_trans_t *_xfs_trans_alloc(struct xfs_mount *, uint, uint, bool);
static inline struct xfs_trans *
xfs_trans_alloc(struct xfs_mount *mp, uint type)
{
return _xfs_trans_alloc(mp, type, KM_SLEEP, true);
}
xfs_trans_t *xfs_trans_dup(xfs_trans_t *);
int xfs_trans_reserve(xfs_trans_t *, uint, uint, uint,
uint, uint);