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Revert "xfs: fix filesystsem freeze race in xfs_trans_alloc" 

This reverts commit 7a249cf83d.

That commit created a situation that could lead to a filesystem
hang.  As Dave Chinner pointed out, xfs_trans_alloc() could hold a
reference to m_active_trans (i.e., keep it non-zero) and then wait
for SB_FREEZE_TRANS to complete.  Meanwhile a filesystem freeze
request could set SB_FREEZE_TRANS and then wait for m_active_trans
to drop to zero.  Nobody benefits from this sequence of events...

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>
This commit is contained in:
Alex Elder 2011-07-11 09:51:44 -05:00
parent 81463b1ca8
commit b2ce397400
5 changed files with 30 additions and 28 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, false);
tp = _xfs_trans_alloc(mp, XFS_TRANS_DUMMY1, KM_SLEEP);
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

@ -688,7 +688,8 @@ xfs_iomap_write_unwritten(
* the same inode that we complete here and might deadlock
* on the iolock.
*/
tp = _xfs_trans_alloc(mp, XFS_TRANS_STRAT_WRITE, KM_NOFS, true);
xfs_wait_for_freeze(mp, SB_FREEZE_TRANS);
tp = _xfs_trans_alloc(mp, XFS_TRANS_STRAT_WRITE, KM_NOFS);
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

@ -1559,9 +1559,15 @@ 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(
@ -1583,13 +1589,7 @@ xfs_log_sbcount(
if (!xfs_sb_version_haslazysbcount(&mp->m_sb))
return 0;
/*
* 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);
tp = _xfs_trans_alloc(mp, XFS_TRANS_SB_COUNT, KM_SLEEP);
error = xfs_trans_reserve(tp, 0, mp->m_sb.sb_sectsize + 128, 0, 0,
XFS_DEFAULT_LOG_COUNT);
if (error) {

29
fs/xfs/xfs_trans.c
View File

@ -566,24 +566,31 @@ 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.
*/
struct xfs_trans *
_xfs_trans_alloc(
struct xfs_mount *mp,
uint type,
uint memflags,
bool wait_for_freeze)
xfs_trans_t *
xfs_trans_alloc(
xfs_mount_t *mp,
uint type)
{
struct xfs_trans *tp;
xfs_wait_for_freeze(mp, SB_FREEZE_TRANS);
return _xfs_trans_alloc(mp, type, KM_SLEEP);
}
xfs_trans_t *
_xfs_trans_alloc(
xfs_mount_t *mp,
uint type,
uint memflags)
{
xfs_trans_t *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

@ -447,14 +447,8 @@ typedef struct xfs_trans {
/*
* XFS transaction mechanism exported interfaces.
*/
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_alloc(struct xfs_mount *, uint);
xfs_trans_t *_xfs_trans_alloc(struct xfs_mount *, uint, uint);
xfs_trans_t *xfs_trans_dup(xfs_trans_t *);
int xfs_trans_reserve(xfs_trans_t *, uint, uint, uint,
uint, uint);