Revert "xfs: fix filesystsem freeze race in xfs_trans_alloc"

This reverts commit 7a249cf83da1813cfa71cfe1e265b40045eceb47.

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>

5 files changed, 29 insertions, 27 deletions

diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
index b7c492d293b5..9153d2c77caf 100644
--- a/fs/xfs/xfs_fsops.c
+++ b/fs/xfs/xfs_fsops.c
@@ -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) {
diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 982b71108f33..091d82b94c4d 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -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,
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index 2be5e5cf897a..a19e92381f90 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -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) {
diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
index 2837220ea5cf..c83f63b33aae 100644
--- a/fs/xfs/xfs_trans.c
+++ b/fs/xfs/xfs_trans.c
@@ -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,
-        uint                    type,
-        uint                    memflags,
-        bool                    wait_for_freeze)
+        xfs_mount_t     *mp,
+        uint            type,
+        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;
diff --git a/fs/xfs/xfs_trans.h b/fs/xfs/xfs_trans.h
index 4e78432ce143..06a9759b6352 100644
--- a/fs/xfs/xfs_trans.h
+++ b/fs/xfs/xfs_trans.h
@@ -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);