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Commit b2ce3974 authored by Alex Elder's avatar Alex Elder
Browse files

Revert "xfs: fix filesystsem freeze race in xfs_trans_alloc" 



This reverts commit 7a249cf8.

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: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarAlex Elder <aelder@sgi.com>
parent 81463b1c

fs/xfs/xfs_fsops.c

+1 −1
Original line number Diff line number Diff line
@@ -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) {

fs/xfs/xfs_iomap.c

+2 −1
Original line number Diff line number Diff line
@@ -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,

fs/xfs/xfs_mount.c

+7 −7
Original line number Diff line number Diff line
@@ -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) {

fs/xfs/xfs_trans.c

+17 −10
Original line number Diff line number Diff line
@@ -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_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 *

_xfs_trans_alloc(

	struct xfs_mount	*mp,

	xfs_mount_t	*mp,

	uint		type,

	uint			memflags,

	bool			wait_for_freeze)

	uint		memflags)

{

	struct xfs_trans	*tp;

	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;

fs/xfs/xfs_trans.h

+2 −8
Original line number Diff line number Diff line
@@ -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);