[PATCH 01/13] xfs: xfs_iflock is no longer a completion

Dave Chinner
2020-08-12T09:26:07Z

From: Dave Chinner <dchinner@redhat.com>

With the recent rework of the inode cluster flushing, we no longer
ever wait on the the inode flush "lock". It was never a lock in the
first place, just a completion to allow callers to wait for inode IO
to complete. We now never wait for flush completion as all inode
flushing is non-blocking. Hence we can get rid of all the iflock
infrastructure and instead just set and check a state flag.

Rename the XFS_IFLOCK flag to XFS_IFLUSHING, convert all the
xfs_iflock_nowait() test-and-set operations on that flag, and
replace all the xfs_ifunlock() calls to clear operations.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
fs/xfs/xfs_icache.c | 17 ++++------
fs/xfs/xfs_inode.c | 73 +++++++++++++++--------------------------
fs/xfs/xfs_inode.h | 33 +------------------
fs/xfs/xfs_inode_item.c | 15 ++++-----
fs/xfs/xfs_inode_item.h | 4 +--
fs/xfs/xfs_mount.c | 11 ++++---
fs/xfs/xfs_super.c | 10 +++---
7 files changed, 55 insertions(+), 108 deletions(-)

diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
index 101028ebb571..aa6aad258670 100644
--- a/fs/xfs/xfs_icache.c
+++ b/fs/xfs/xfs_icache.c
@@ -52,7 +52,6 @@ xfs_inode_alloc(

XFS_STATS_INC(mp, vn_active);
ASSERT(atomic_read(&ip->i_pincount) == 0);
- ASSERT(!xfs_isiflocked(ip));
ASSERT(ip->i_ino == 0);

/* initialise the xfs inode */
@@ -123,7 +122,7 @@ void
xfs_inode_free(
struct xfs_inode *ip)
{
- ASSERT(!xfs_isiflocked(ip));
+ ASSERT(!xfs_iflags_test(ip, XFS_IFLUSHING));

/*
* Because we use RCU freeing we need to ensure the inode always
@@ -1035,23 +1034,21 @@ xfs_reclaim_inode(

if (!xfs_ilock_nowait(ip, XFS_ILOCK_EXCL))
goto out;
- if (!xfs_iflock_nowait(ip))
+ if (xfs_iflags_test_and_set(ip, XFS_IFLUSHING))
goto out_iunlock;

if (XFS_FORCED_SHUTDOWN(ip->i_mount)) {
xfs_iunpin_wait(ip);
- /* xfs_iflush_abort() drops the flush lock */
xfs_iflush_abort(ip);
goto reclaim;
}
if (xfs_ipincount(ip))
- goto out_ifunlock;
+ goto out_clear_flush;
if (!xfs_inode_clean(ip))
- goto out_ifunlock;
+ goto out_clear_flush;

- xfs_ifunlock(ip);
+ xfs_iflags_clear(ip, XFS_IFLUSHING);
reclaim:
- ASSERT(!xfs_isiflocked(ip));

/*
* Because we use RCU freeing we need to ensure the inode always appears
@@ -1101,8 +1098,8 @@ xfs_reclaim_inode(
__xfs_inode_free(ip);
return;

-out_ifunlock:
- xfs_ifunlock(ip);
+out_clear_flush:
+ xfs_iflags_clear(ip, XFS_IFLUSHING);
out_iunlock:
xfs_iunlock(ip, XFS_ILOCK_EXCL);
out:
diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index c06129cffba9..2072bd25989a 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -598,22 +598,6 @@ xfs_lock_two_inodes(
}
}

-void
-__xfs_iflock(
- struct xfs_inode *ip)
-{
- wait_queue_head_t *wq = bit_waitqueue(&ip->i_flags, __XFS_IFLOCK_BIT);
- DEFINE_WAIT_BIT(wait, &ip->i_flags, __XFS_IFLOCK_BIT);
-
- do {
- prepare_to_wait_exclusive(wq, &wait.wq_entry, TASK_UNINTERRUPTIBLE);
- if (xfs_isiflocked(ip))
- io_schedule();
- } while (!xfs_iflock_nowait(ip));
-
- finish_wait(wq, &wait.wq_entry);
-}
-
STATIC uint
_xfs_dic2xflags(
uint16_t di_flags,
@@ -2531,11 +2515,8 @@ xfs_ifree_mark_inode_stale(
* valid, the wrong inode or stale.
*/
spin_lock(&ip->i_flags_lock);
- if (ip->i_ino != inum || __xfs_iflags_test(ip, XFS_ISTALE)) {
- spin_unlock(&ip->i_flags_lock);
- rcu_read_unlock();
- return;
- }
+ if (ip->i_ino != inum || __xfs_iflags_test(ip, XFS_ISTALE))
+ goto out_iflags_unlock;

/*
* Don't try to lock/unlock the current inode, but we _cannot_ skip the
@@ -2552,16 +2533,14 @@ xfs_ifree_mark_inode_stale(
}
}
ip->i_flags |= XFS_ISTALE;
- spin_unlock(&ip->i_flags_lock);
- rcu_read_unlock();

/*
- * If we can't get the flush lock, the inode is already attached. All
+ * If the inode is flushing, it is already attached to the buffer. All
* we needed to do here is mark the inode stale so buffer IO completion
* will remove it from the AIL.
*/
iip = ip->i_itemp;
- if (!xfs_iflock_nowait(ip)) {
+ if (__xfs_iflags_test(ip, XFS_IFLUSHING)) {
ASSERT(!list_empty(&iip->ili_item.li_bio_list));
ASSERT(iip->ili_last_fields);
goto out_iunlock;
@@ -2573,10 +2552,12 @@ xfs_ifree_mark_inode_stale(
* commit as the flock synchronises removal of the inode from the
* cluster buffer against inode reclaim.
*/
- if (!iip || list_empty(&iip->ili_item.li_bio_list)) {
- xfs_ifunlock(ip);
+ if (!iip || list_empty(&iip->ili_item.li_bio_list))
goto out_iunlock;
- }
+
+ __xfs_iflags_set(ip, XFS_IFLUSHING);
+ spin_unlock(&ip->i_flags_lock);
+ rcu_read_unlock();

/* we have a dirty inode in memory that has not yet been flushed. */
spin_lock(&iip->ili_lock);
@@ -2586,9 +2567,16 @@ xfs_ifree_mark_inode_stale(
spin_unlock(&iip->ili_lock);
ASSERT(iip->ili_last_fields);

+ if (ip != free_ip)
+ xfs_iunlock(ip, XFS_ILOCK_EXCL);
+ return;
+
out_iunlock:
if (ip != free_ip)
xfs_iunlock(ip, XFS_ILOCK_EXCL);
+out_iflags_unlock:
+ spin_unlock(&ip->i_flags_lock);
+ rcu_read_unlock();
}

/*
@@ -2631,8 +2619,9 @@ xfs_ifree_cluster(

/*
* We obtain and lock the backing buffer first in the process
- * here, as we have to ensure that any dirty inode that we
- * can't get the flush lock on is attached to the buffer.
+ * here to ensure dirty inodes attached to the buffer remain in
+ * the flushing state while we mark them stale.
+ *
* If we scan the in-memory inodes first, then buffer IO can
* complete before we get a lock on it, and hence we may fail
* to mark all the active inodes on the buffer stale.
@@ -3443,7 +3432,7 @@ xfs_iflush(
int error;

ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL|XFS_ILOCK_SHARED));
- ASSERT(xfs_isiflocked(ip));
+ ASSERT(xfs_iflags_test(ip, XFS_IFLUSHING));
ASSERT(ip->i_df.if_format != XFS_DINODE_FMT_BTREE ||
ip->i_df.if_nextents > XFS_IFORK_MAXEXT(ip, XFS_DATA_FORK));
ASSERT(iip->ili_item.li_buf == bp);
@@ -3613,7 +3602,7 @@ xfs_iflush_cluster(
/*
* Quick and dirty check to avoid locks if possible.
*/
- if (__xfs_iflags_test(ip, XFS_IRECLAIM | XFS_IFLOCK))
+ if (__xfs_iflags_test(ip, XFS_IRECLAIM | XFS_IFLUSHING))
continue;
if (xfs_ipincount(ip))
continue;
@@ -3627,7 +3616,7 @@ xfs_iflush_cluster(
*/
spin_lock(&ip->i_flags_lock);
ASSERT(!__xfs_iflags_test(ip, XFS_ISTALE));
- if (__xfs_iflags_test(ip, XFS_IRECLAIM | XFS_IFLOCK)) {
+ if (__xfs_iflags_test(ip, XFS_IRECLAIM | XFS_IFLUSHING)) {
spin_unlock(&ip->i_flags_lock);
continue;
}
@@ -3635,23 +3624,16 @@ xfs_iflush_cluster(
/*
* ILOCK will pin the inode against reclaim and prevent
* concurrent transactions modifying the inode while we are
- * flushing the inode.
+ * flushing the inode. If we get the lock, set the flushing
+ * state before we drop the i_flags_lock.
*/
if (!xfs_ilock_nowait(ip, XFS_ILOCK_SHARED)) {
spin_unlock(&ip->i_flags_lock);
continue;
}
+ __xfs_iflags_set(ip, XFS_IFLUSHING);
spin_unlock(&ip->i_flags_lock);

- /*
- * Skip inodes that are already flush locked as they have
- * already been written to the buffer.
- */
- if (!xfs_iflock_nowait(ip)) {
- xfs_iunlock(ip, XFS_ILOCK_SHARED);
- continue;
- }
-
/*
* Abort flushing this inode if we are shut down because the
* inode may not currently be in the AIL. This can occur when
@@ -3661,7 +3643,6 @@ xfs_iflush_cluster(
*/
if (XFS_FORCED_SHUTDOWN(mp)) {
xfs_iunpin_wait(ip);
- /* xfs_iflush_abort() drops the flush lock */
xfs_iflush_abort(ip);
xfs_iunlock(ip, XFS_ILOCK_SHARED);
error = -EIO;
@@ -3670,7 +3651,7 @@ xfs_iflush_cluster(

/* don't block waiting on a log force to unpin dirty inodes */
if (xfs_ipincount(ip)) {
- xfs_ifunlock(ip);
+ xfs_iflags_clear(ip, XFS_IFLUSHING);
xfs_iunlock(ip, XFS_ILOCK_SHARED);
continue;
}
@@ -3678,7 +3659,7 @@ xfs_iflush_cluster(
if (!xfs_inode_clean(ip))
error = xfs_iflush(ip, bp);
else
- xfs_ifunlock(ip);
+ xfs_iflags_clear(ip, XFS_IFLUSHING);
xfs_iunlock(ip, XFS_ILOCK_SHARED);
if (error)
break;
diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
index e9a8bb184d1f..5ea962c6cf98 100644
--- a/fs/xfs/xfs_inode.h
+++ b/fs/xfs/xfs_inode.h
@@ -211,8 +211,7 @@ static inline bool xfs_inode_has_cow_data(struct xfs_inode *ip)
#define XFS_INEW (1 << __XFS_INEW_BIT)
#define XFS_ITRUNCATED (1 << 5) /* truncated down so flush-on-close */
#define XFS_IDIRTY_RELEASE (1 << 6) /* dirty release already seen */
-#define __XFS_IFLOCK_BIT 7 /* inode is being flushed right now */
-#define XFS_IFLOCK (1 << __XFS_IFLOCK_BIT)
+#define XFS_IFLUSHING (1 << 7) /* inode is being flushed */
#define __XFS_IPINNED_BIT 8 /* wakeup key for zero pin count */
#define XFS_IPINNED (1 << __XFS_IPINNED_BIT)
#define XFS_IEOFBLOCKS (1 << 9) /* has the preallocblocks tag set */
@@ -233,36 +232,6 @@ static inline bool xfs_inode_has_cow_data(struct xfs_inode *ip)
(XFS_IRECLAIMABLE | XFS_IRECLAIM | \
XFS_IDIRTY_RELEASE | XFS_ITRUNCATED)

-/*
- * Synchronize processes attempting to flush the in-core inode back to disk.
- */
-
-static inline int xfs_isiflocked(struct xfs_inode *ip)
-{
- return xfs_iflags_test(ip, XFS_IFLOCK);
-}
-
-extern void __xfs_iflock(struct xfs_inode *ip);
-
-static inline int xfs_iflock_nowait(struct xfs_inode *ip)
-{
- return !xfs_iflags_test_and_set(ip, XFS_IFLOCK);
-}
-
-static inline void xfs_iflock(struct xfs_inode *ip)
-{
- if (!xfs_iflock_nowait(ip))
- __xfs_iflock(ip);
-}
-
-static inline void xfs_ifunlock(struct xfs_inode *ip)
-{
- ASSERT(xfs_isiflocked(ip));
- xfs_iflags_clear(ip, XFS_IFLOCK);
- smp_mb();
- wake_up_bit(&ip->i_flags, __XFS_IFLOCK_BIT);
-}
-
/*
* Flags for inode locking.
* Bit ranges: 1<<1 - 1<<16-1 -- iolock/ilock modes (bitfield)
diff --git a/fs/xfs/xfs_inode_item.c b/fs/xfs/xfs_inode_item.c
index 6c65938cee1c..099ae8ee7908 100644
--- a/fs/xfs/xfs_inode_item.c
+++ b/fs/xfs/xfs_inode_item.c
@@ -491,8 +491,7 @@ xfs_inode_item_push(
(ip->i_flags & XFS_ISTALE))
return XFS_ITEM_PINNED;

- /* If the inode is already flush locked, we're already flushing. */
- if (xfs_isiflocked(ip))
+ if (xfs_iflags_test(ip, XFS_IFLUSHING))
return XFS_ITEM_FLUSHING;

if (!xfs_buf_trylock(bp))
@@ -703,7 +702,7 @@ xfs_iflush_finish(
iip->ili_last_fields = 0;
iip->ili_flush_lsn = 0;
spin_unlock(&iip->ili_lock);
- xfs_ifunlock(iip->ili_inode);
+ xfs_iflags_clear(iip->ili_inode, XFS_IFLUSHING);
if (drop_buffer)
xfs_buf_rele(bp);
}
@@ -711,8 +710,8 @@ xfs_iflush_finish(

/*
* Inode buffer IO completion routine. It is responsible for removing inodes
- * attached to the buffer from the AIL if they have not been re-logged, as well
- * as completing the flush and unlocking the inode.
+ * attached to the buffer from the AIL if they have not been re-logged and
+ * completing the inode flush.
*/
void
xfs_iflush_done(
@@ -755,10 +754,10 @@ xfs_iflush_done(
}

/*
- * This is the inode flushing abort routine. It is called from xfs_iflush when
+ * This is the inode flushing abort routine. It is called when
* the filesystem is shutting down to clean up the inode state. It is
* responsible for removing the inode item from the AIL if it has not been
- * re-logged, and unlocking the inode's flush lock.
+ * re-logged and clearing the inode's flush state.
*/
void
xfs_iflush_abort(
@@ -790,7 +789,7 @@ xfs_iflush_abort(
list_del_init(&iip->ili_item.li_bio_list);
spin_unlock(&iip->ili_lock);
}
- xfs_ifunlock(ip);
+ xfs_iflags_clear(ip, XFS_IFLUSHING);
if (bp)
xfs_buf_rele(bp);
}
diff --git a/fs/xfs/xfs_inode_item.h b/fs/xfs/xfs_inode_item.h
index 048b5e7dee90..23a7b4928727 100644
--- a/fs/xfs/xfs_inode_item.h
+++ b/fs/xfs/xfs_inode_item.h
@@ -25,8 +25,8 @@ struct xfs_inode_log_item {
*
* We need atomic changes between inode dirtying, inode flushing and
* inode completion, but these all hold different combinations of
- * ILOCK and iflock and hence we need some other method of serialising
- * updates to the flush state.
+ * ILOCK and IFLUSHING and hence we need some other method of
+ * serialising updates to the flush state.
*/
spinlock_t ili_lock; /* flush state lock */
unsigned int ili_last_fields; /* fields when flushed */
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index c8ae49a1e99c..bbfd1d5b1c04 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -1059,11 +1059,12 @@ xfs_unmountfs(
* We can potentially deadlock here if we have an inode cluster
* that has been freed has its buffer still pinned in memory because
* the transaction is still sitting in a iclog. The stale inodes
- * on that buffer will have their flush locks held until the
- * transaction hits the disk and the callbacks run. the inode
- * flush takes the flush lock unconditionally and with nothing to
- * push out the iclog we will never get that unlocked. hence we
- * need to force the log first.
+ * on that buffer will be pinned to the buffer until the
+ * transaction hits the disk and the callbacks run. Pushing the AIL will
+ * skip the stale inodes and may never see the pinned buffer, so
+ * nothing will push out the iclog and unpin the buffer. Hence we
+ * need to force the log here to ensure all items are flushed into the
+ * AIL before we go any further.
*/
xfs_log_force(mp, XFS_LOG_SYNC);

diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index 71ac6c1cdc36..68ec8db12cc7 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -654,11 +654,11 @@ xfs_fs_destroy_inode(
ASSERT_ALWAYS(!xfs_iflags_test(ip, XFS_IRECLAIM));

/*
- * We always use background reclaim here because even if the
- * inode is clean, it still may be under IO and hence we have
- * to take the flush lock. The background reclaim path handles
- * this more efficiently than we can here, so simply let background
- * reclaim tear down all inodes.
+ * We always use background reclaim here because even if the inode is
+ * clean, it still may be under IO and hence we have wait for IO
+ * completion to occur before we can reclaim the inode. The background
+ * reclaim path handles this more efficiently than we can here, so
+ * simply let background reclaim tear down all inodes.
*/
xfs_inode_set_reclaim_tag(ip);
}
--
2.26.2.761.g0e0b3e54be