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SubjectRe: [PATCH 6/8] xfs: Use generic writers counter instead of m_active_trans counter
On 1/20/12 2:34 PM, Jan Kara wrote:
> m_active_trans counter is racy wrt filesystem freezing. The patch replaces it
> with generic counter of running transactions which is properly synchronized
> with filesystem freezing. Things are a bit more complex because we need to log
> a dummy transaction and free block counters after the filesystem is frozen so
> we need to pass information to _xfs_trans_alloc() whether the transaction is
> part of filesystem freezing or not.

Here's the version I have which will get me past xfstest 068 and avoids
some warnings.

This version brings the sb_start_write go/nogo flag up to
xfs_log_sbcount() to avoid a warning at unmount time.

I'd still like to make some of the variable/macro naming more obvious
but this might do for now.

diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
index 1c6fdeb..503fdfa 100644
--- a/fs/xfs/xfs_fsops.c
+++ b/fs/xfs/xfs_fsops.c
@@ -645,12 +645,13 @@ out:
*/
int
xfs_fs_log_dummy(
- xfs_mount_t *mp)
+ xfs_mount_t *mp,
+ bool for_freeze)
{
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, for_freeze);
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_fsops.h b/fs/xfs/xfs_fsops.h
index 1b6a98b..4d6253e 100644
--- a/fs/xfs/xfs_fsops.h
+++ b/fs/xfs/xfs_fsops.h
@@ -25,6 +25,6 @@ extern int xfs_fs_counts(xfs_mount_t *mp, xfs_fsop_counts_t *cnt);
extern int xfs_reserve_blocks(xfs_mount_t *mp, __uint64_t *inval,
xfs_fsop_resblks_t *outval);
extern int xfs_fs_goingdown(xfs_mount_t *mp, __uint32_t inflags);
-extern int xfs_fs_log_dummy(struct xfs_mount *mp);
+extern int xfs_fs_log_dummy(struct xfs_mount *mp, bool for_freeze);

#endif /* __XFS_FSOPS_H__ */
diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 246c7d5..99f4e42 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -679,8 +679,8 @@ 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, XFS_HONOR_FREEZE_TRANS);
tp->t_flags |= XFS_TRANS_RESERVE;
error = xfs_trans_reserve(tp, resblks,
XFS_WRITE_LOG_RES(mp), 0,
diff --git a/fs/xfs/xfs_linux.h b/fs/xfs/xfs_linux.h
index 828662f..b2731ea 100644
--- a/fs/xfs/xfs_linux.h
+++ b/fs/xfs/xfs_linux.h
@@ -308,4 +308,7 @@ static inline __uint64_t howmany_64(__uint64_t x, __uint32_t y)

#endif /* DEBUG */

+#define XFS_HONOR_FREEZE_TRANS false
+#define XFS_IGNORE_FREEZE_TRANS true
+
#endif /* __XFS_LINUX__ */
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index d06afbc..663bc96 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -1513,7 +1513,7 @@ xfs_unmountfs(
xfs_warn(mp, "Unable to free reserved block pool. "
"Freespace may not be correct on next mount.");

- error = xfs_log_sbcount(mp);
+ error = xfs_log_sbcount(mp, XFS_HONOR_FREEZE_TRANS);
if (error)
xfs_warn(mp, "Unable to update superblock counters. "
"Freespace may not be correct on next mount.");
@@ -1555,7 +1555,7 @@ xfs_fs_writable(xfs_mount_t *mp)
* block when the transaction subsystem is in its frozen state.
*/
int
-xfs_log_sbcount(xfs_mount_t *mp)
+xfs_log_sbcount(xfs_mount_t *mp, int freezing)
{
xfs_trans_t *tp;
int error;
@@ -1572,7 +1572,7 @@ xfs_log_sbcount(xfs_mount_t *mp)
if (!xfs_sb_version_haslazysbcount(&mp->m_sb))
return 0;

- tp = _xfs_trans_alloc(mp, XFS_TRANS_SB_COUNT, KM_SLEEP);
+ tp = _xfs_trans_alloc(mp, XFS_TRANS_SB_COUNT, KM_SLEEP, freezing);
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_mount.h b/fs/xfs/xfs_mount.h
index 19f69e2..9319047 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -195,7 +195,6 @@ typedef struct xfs_mount {
uint m_chsize; /* size of next field */
struct xfs_chash *m_chash; /* fs private inode per-cluster
* hash table */
- atomic_t m_active_trans; /* number trans frozen */
#ifdef HAVE_PERCPU_SB
xfs_icsb_cnts_t __percpu *m_sb_cnts; /* per-cpu superblock counters */
unsigned long m_icsb_counters; /* disabled per-cpu counters */
@@ -311,7 +310,6 @@ void xfs_do_force_shutdown(struct xfs_mount *mp, int flags, char *fname,
#define SHUTDOWN_DEVICE_REQ 0x0020 /* failed all paths to the device */

#define xfs_test_for_freeze(mp) ((mp)->m_super->s_frozen)
-#define xfs_wait_for_freeze(mp,l) vfs_check_frozen((mp)->m_super, (l))

/*
* Flags for xfs_mountfs
@@ -370,7 +368,7 @@ typedef struct xfs_mod_sb {
int64_t msb_delta; /* Change to make to specified field */
} xfs_mod_sb_t;

-extern int xfs_log_sbcount(xfs_mount_t *);
+extern int xfs_log_sbcount(xfs_mount_t *, int);
extern __uint64_t xfs_default_resblks(xfs_mount_t *mp);
extern int xfs_mountfs(xfs_mount_t *mp);

diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index ee5b695..a257077 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -1198,7 +1198,7 @@ xfs_fs_freeze(

xfs_save_resvblks(mp);
xfs_quiesce_attr(mp);
- return -xfs_fs_log_dummy(mp);
+ return -xfs_fs_log_dummy(mp, XFS_IGNORE_FREEZE_TRANS);
}

STATIC int
@@ -1285,7 +1285,6 @@ xfs_fs_fill_super(

spin_lock_init(&mp->m_sb_lock);
mutex_init(&mp->m_growlock);
- atomic_set(&mp->m_active_trans, 0);

mp->m_super = sb;
sb->s_fs_info = mp;
diff --git a/fs/xfs/xfs_sync.c b/fs/xfs/xfs_sync.c
index 40b75ee..b9a6be0 100644
--- a/fs/xfs/xfs_sync.c
+++ b/fs/xfs/xfs_sync.c
@@ -406,7 +406,7 @@ xfs_quiesce_data(

/* mark the log as covered if needed */
if (xfs_log_need_covered(mp))
- error2 = xfs_fs_log_dummy(mp);
+ error2 = xfs_fs_log_dummy(mp, XFS_HONOR_FREEZE_TRANS);

/* flush data-only devices */
if (mp->m_rtdev_targp)
@@ -454,20 +454,13 @@ xfs_quiesce_attr(
int error = 0;

/* wait for all modifications to complete */
- while (atomic_read(&mp->m_active_trans) > 0)
- delay(100);
+ sb_wait_write(mp->m_super, SB_FREEZE_TRANS);

/* flush inodes and push all remaining buffers out to disk */
xfs_quiesce_fs(mp);

- /*
- * Just warn here till VFS can correctly support
- * read-only remount without racing.
- */
- WARN_ON(atomic_read(&mp->m_active_trans) != 0);
-
/* Push the superblock and write an unmount record */
- error = xfs_log_sbcount(mp);
+ error = xfs_log_sbcount(mp, XFS_IGNORE_FREEZE_TRANS);
if (error)
xfs_warn(mp, "xfs_attr_quiesce: failed to log sb changes. "
"Frozen image may not be consistent.");
@@ -500,7 +493,7 @@ xfs_sync_worker(
/* dgc: errors ignored here */
if (mp->m_super->s_frozen == SB_UNFROZEN &&
xfs_log_need_covered(mp))
- error = xfs_fs_log_dummy(mp);
+ error = xfs_fs_log_dummy(mp, XFS_HONOR_FREEZE_TRANS);
else
xfs_log_force(mp, 0);

diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
index 329b06a..dda8877 100644
--- a/fs/xfs/xfs_trans.c
+++ b/fs/xfs/xfs_trans.c
@@ -577,24 +577,28 @@ 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);
+ return _xfs_trans_alloc(mp, type, KM_SLEEP, XFS_HONOR_FREEZE_TRANS);
}

xfs_trans_t *
_xfs_trans_alloc(
xfs_mount_t *mp,
uint type,
- uint memflags)
+ uint memflags,
+ bool freezing)
{
xfs_trans_t *tp;

- atomic_inc(&mp->m_active_trans);
-
+ if (!freezing)
+ sb_start_write(mp->m_super, SB_FREEZE_TRANS);
+ else
+ WARN_ON(xfs_test_for_freeze(mp) != SB_FREEZE_TRANS);
tp = kmem_zone_zalloc(xfs_trans_zone, memflags);
tp->t_magic = XFS_TRANS_MAGIC;
tp->t_type = type;
tp->t_mountp = mp;
+ if (freezing)
+ tp->t_flags |= XFS_TRANS_FREEZING;
INIT_LIST_HEAD(&tp->t_items);
INIT_LIST_HEAD(&tp->t_busy);
return tp;
@@ -611,7 +615,8 @@ xfs_trans_free(
xfs_alloc_busy_sort(&tp->t_busy);
xfs_alloc_busy_clear(tp->t_mountp, &tp->t_busy, false);

- atomic_dec(&tp->t_mountp->m_active_trans);
+ if (!(tp->t_flags & XFS_TRANS_FREEZING))
+ sb_end_write(tp->t_mountp->m_super, SB_FREEZE_TRANS);
xfs_trans_free_dqinfo(tp);
kmem_zone_free(xfs_trans_zone, tp);
}
@@ -654,7 +659,10 @@ xfs_trans_dup(

xfs_trans_dup_dqinfo(tp, ntp);

- atomic_inc(&tp->t_mountp->m_active_trans);
+ if (tp->t_flags & XFS_TRANS_FREEZING)
+ ntp->t_flags |= XFS_TRANS_FREEZING;
+ else
+ sb_dup_write(tp->t_mountp->m_super, SB_FREEZE_TRANS);
return ntp;
}

diff --git a/fs/xfs/xfs_trans.h b/fs/xfs/xfs_trans.h
index f611870..cae91db 100644
--- a/fs/xfs/xfs_trans.h
+++ b/fs/xfs/xfs_trans.h
@@ -179,6 +179,7 @@ struct xfs_log_item_desc {
#define XFS_TRANS_SYNC 0x08 /* make commit synchronous */
#define XFS_TRANS_DQ_DIRTY 0x10 /* at least one dquot in trx dirty */
#define XFS_TRANS_RESERVE 0x20 /* OK to use reserved data blocks */
+#define XFS_TRANS_FREEZING 0x40 /* can happen on frozen filesystem */

/*
* Values for call flags parameter.
@@ -447,7 +448,7 @@ 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);
xfs_trans_t *xfs_trans_dup(xfs_trans_t *);
int xfs_trans_reserve(xfs_trans_t *, uint, uint, uint,
uint, uint);




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