Merge branch 'xfs-4.8-buf-fixes' into for-next
diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index 4665ff6..32fc5401 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -80,6 +80,47 @@
}
/*
+ * Bump the I/O in flight count on the buftarg if we haven't yet done so for
+ * this buffer. The count is incremented once per buffer (per hold cycle)
+ * because the corresponding decrement is deferred to buffer release. Buffers
+ * can undergo I/O multiple times in a hold-release cycle and per buffer I/O
+ * tracking adds unnecessary overhead. This is used for sychronization purposes
+ * with unmount (see xfs_wait_buftarg()), so all we really need is a count of
+ * in-flight buffers.
+ *
+ * Buffers that are never released (e.g., superblock, iclog buffers) must set
+ * the XBF_NO_IOACCT flag before I/O submission. Otherwise, the buftarg count
+ * never reaches zero and unmount hangs indefinitely.
+ */
+static inline void
+xfs_buf_ioacct_inc(
+ struct xfs_buf *bp)
+{
+ if (bp->b_flags & (XBF_NO_IOACCT|_XBF_IN_FLIGHT))
+ return;
+
+ ASSERT(bp->b_flags & XBF_ASYNC);
+ bp->b_flags |= _XBF_IN_FLIGHT;
+ percpu_counter_inc(&bp->b_target->bt_io_count);
+}
+
+/*
+ * Clear the in-flight state on a buffer about to be released to the LRU or
+ * freed and unaccount from the buftarg.
+ */
+static inline void
+xfs_buf_ioacct_dec(
+ struct xfs_buf *bp)
+{
+ if (!(bp->b_flags & _XBF_IN_FLIGHT))
+ return;
+
+ ASSERT(bp->b_flags & XBF_ASYNC);
+ bp->b_flags &= ~_XBF_IN_FLIGHT;
+ percpu_counter_dec(&bp->b_target->bt_io_count);
+}
+
+/*
* When we mark a buffer stale, we remove the buffer from the LRU and clear the
* b_lru_ref count so that the buffer is freed immediately when the buffer
* reference count falls to zero. If the buffer is already on the LRU, we need
@@ -102,6 +143,14 @@
*/
bp->b_flags &= ~_XBF_DELWRI_Q;
+ /*
+ * Once the buffer is marked stale and unlocked, a subsequent lookup
+ * could reset b_flags. There is no guarantee that the buffer is
+ * unaccounted (released to LRU) before that occurs. Drop in-flight
+ * status now to preserve accounting consistency.
+ */
+ xfs_buf_ioacct_dec(bp);
+
spin_lock(&bp->b_lock);
atomic_set(&bp->b_lru_ref, 0);
if (!(bp->b_state & XFS_BSTATE_DISPOSE) &&
@@ -815,7 +864,8 @@
struct xfs_buf *bp;
DEFINE_SINGLE_BUF_MAP(map, XFS_BUF_DADDR_NULL, numblks);
- bp = _xfs_buf_alloc(target, &map, 1, 0);
+ /* flags might contain irrelevant bits, pass only what we care about */
+ bp = _xfs_buf_alloc(target, &map, 1, flags & XBF_NO_IOACCT);
if (unlikely(bp == NULL))
goto fail;
@@ -866,63 +916,85 @@
}
/*
- * Releases a hold on the specified buffer. If the
- * the hold count is 1, calls xfs_buf_free.
+ * Release a hold on the specified buffer. If the hold count is 1, the buffer is
+ * placed on LRU or freed (depending on b_lru_ref).
*/
void
xfs_buf_rele(
xfs_buf_t *bp)
{
struct xfs_perag *pag = bp->b_pag;
+ bool release;
+ bool freebuf = false;
trace_xfs_buf_rele(bp, _RET_IP_);
if (!pag) {
ASSERT(list_empty(&bp->b_lru));
ASSERT(RB_EMPTY_NODE(&bp->b_rbnode));
- if (atomic_dec_and_test(&bp->b_hold))
+ if (atomic_dec_and_test(&bp->b_hold)) {
+ xfs_buf_ioacct_dec(bp);
xfs_buf_free(bp);
+ }
return;
}
ASSERT(!RB_EMPTY_NODE(&bp->b_rbnode));
ASSERT(atomic_read(&bp->b_hold) > 0);
- if (atomic_dec_and_lock(&bp->b_hold, &pag->pag_buf_lock)) {
- spin_lock(&bp->b_lock);
- if (!(bp->b_flags & XBF_STALE) && atomic_read(&bp->b_lru_ref)) {
- /*
- * If the buffer is added to the LRU take a new
- * reference to the buffer for the LRU and clear the
- * (now stale) dispose list state flag
- */
- if (list_lru_add(&bp->b_target->bt_lru, &bp->b_lru)) {
- bp->b_state &= ~XFS_BSTATE_DISPOSE;
- atomic_inc(&bp->b_hold);
- }
- spin_unlock(&bp->b_lock);
- spin_unlock(&pag->pag_buf_lock);
- } else {
- /*
- * most of the time buffers will already be removed from
- * the LRU, so optimise that case by checking for the
- * XFS_BSTATE_DISPOSE flag indicating the last list the
- * buffer was on was the disposal list
- */
- if (!(bp->b_state & XFS_BSTATE_DISPOSE)) {
- list_lru_del(&bp->b_target->bt_lru, &bp->b_lru);
- } else {
- ASSERT(list_empty(&bp->b_lru));
- }
- spin_unlock(&bp->b_lock);
- ASSERT(!(bp->b_flags & _XBF_DELWRI_Q));
- rb_erase(&bp->b_rbnode, &pag->pag_buf_tree);
- spin_unlock(&pag->pag_buf_lock);
- xfs_perag_put(pag);
- xfs_buf_free(bp);
- }
+ release = atomic_dec_and_lock(&bp->b_hold, &pag->pag_buf_lock);
+ spin_lock(&bp->b_lock);
+ if (!release) {
+ /*
+ * Drop the in-flight state if the buffer is already on the LRU
+ * and it holds the only reference. This is racy because we
+ * haven't acquired the pag lock, but the use of _XBF_IN_FLIGHT
+ * ensures the decrement occurs only once per-buf.
+ */
+ if ((atomic_read(&bp->b_hold) == 1) && !list_empty(&bp->b_lru))
+ xfs_buf_ioacct_dec(bp);
+ goto out_unlock;
}
+
+ /* the last reference has been dropped ... */
+ xfs_buf_ioacct_dec(bp);
+ if (!(bp->b_flags & XBF_STALE) && atomic_read(&bp->b_lru_ref)) {
+ /*
+ * If the buffer is added to the LRU take a new reference to the
+ * buffer for the LRU and clear the (now stale) dispose list
+ * state flag
+ */
+ if (list_lru_add(&bp->b_target->bt_lru, &bp->b_lru)) {
+ bp->b_state &= ~XFS_BSTATE_DISPOSE;
+ atomic_inc(&bp->b_hold);
+ }
+ spin_unlock(&pag->pag_buf_lock);
+ } else {
+ /*
+ * most of the time buffers will already be removed from the
+ * LRU, so optimise that case by checking for the
+ * XFS_BSTATE_DISPOSE flag indicating the last list the buffer
+ * was on was the disposal list
+ */
+ if (!(bp->b_state & XFS_BSTATE_DISPOSE)) {
+ list_lru_del(&bp->b_target->bt_lru, &bp->b_lru);
+ } else {
+ ASSERT(list_empty(&bp->b_lru));
+ }
+
+ ASSERT(!(bp->b_flags & _XBF_DELWRI_Q));
+ rb_erase(&bp->b_rbnode, &pag->pag_buf_tree);
+ spin_unlock(&pag->pag_buf_lock);
+ xfs_perag_put(pag);
+ freebuf = true;
+ }
+
+out_unlock:
+ spin_unlock(&bp->b_lock);
+
+ if (freebuf)
+ xfs_buf_free(bp);
}
@@ -1341,6 +1413,7 @@
* xfs_buf_ioend too early.
*/
atomic_set(&bp->b_io_remaining, 1);
+ xfs_buf_ioacct_inc(bp);
_xfs_buf_ioapply(bp);
/*
@@ -1526,13 +1599,19 @@
int loop = 0;
/*
- * We need to flush the buffer workqueue to ensure that all IO
- * completion processing is 100% done. Just waiting on buffer locks is
- * not sufficient for async IO as the reference count held over IO is
- * not released until after the buffer lock is dropped. Hence we need to
- * ensure here that all reference counts have been dropped before we
- * start walking the LRU list.
+ * First wait on the buftarg I/O count for all in-flight buffers to be
+ * released. This is critical as new buffers do not make the LRU until
+ * they are released.
+ *
+ * Next, flush the buffer workqueue to ensure all completion processing
+ * has finished. Just waiting on buffer locks is not sufficient for
+ * async IO as the reference count held over IO is not released until
+ * after the buffer lock is dropped. Hence we need to ensure here that
+ * all reference counts have been dropped before we start walking the
+ * LRU list.
*/
+ while (percpu_counter_sum(&btp->bt_io_count))
+ delay(100);
drain_workqueue(btp->bt_mount->m_buf_workqueue);
/* loop until there is nothing left on the lru list. */
@@ -1629,6 +1708,8 @@
struct xfs_buftarg *btp)
{
unregister_shrinker(&btp->bt_shrinker);
+ ASSERT(percpu_counter_sum(&btp->bt_io_count) == 0);
+ percpu_counter_destroy(&btp->bt_io_count);
list_lru_destroy(&btp->bt_lru);
if (mp->m_flags & XFS_MOUNT_BARRIER)
@@ -1693,6 +1774,9 @@
if (list_lru_init(&btp->bt_lru))
goto error;
+ if (percpu_counter_init(&btp->bt_io_count, 0, GFP_KERNEL))
+ goto error;
+
btp->bt_shrinker.count_objects = xfs_buftarg_shrink_count;
btp->bt_shrinker.scan_objects = xfs_buftarg_shrink_scan;
btp->bt_shrinker.seeks = DEFAULT_SEEKS;
@@ -1834,7 +1918,7 @@
* side. We need to move the buffer onto the io_list
* at this point so the caller can still access it.
*/
- bp->b_flags &= ~(_XBF_DELWRI_Q | XBF_ASYNC | XBF_WRITE_FAIL);
+ bp->b_flags &= ~(_XBF_DELWRI_Q | XBF_WRITE_FAIL);
bp->b_flags |= XBF_WRITE | XBF_ASYNC;
if (wait_list) {
xfs_buf_hold(bp);
diff --git a/fs/xfs/xfs_buf.h b/fs/xfs/xfs_buf.h
index 8bfb974..1c2e52b 100644
--- a/fs/xfs/xfs_buf.h
+++ b/fs/xfs/xfs_buf.h
@@ -43,6 +43,7 @@
#define XBF_READ (1 << 0) /* buffer intended for reading from device */
#define XBF_WRITE (1 << 1) /* buffer intended for writing to device */
#define XBF_READ_AHEAD (1 << 2) /* asynchronous read-ahead */
+#define XBF_NO_IOACCT (1 << 3) /* bypass I/O accounting (non-LRU bufs) */
#define XBF_ASYNC (1 << 4) /* initiator will not wait for completion */
#define XBF_DONE (1 << 5) /* all pages in the buffer uptodate */
#define XBF_STALE (1 << 6) /* buffer has been staled, do not find it */
@@ -62,6 +63,7 @@
#define _XBF_KMEM (1 << 21)/* backed by heap memory */
#define _XBF_DELWRI_Q (1 << 22)/* buffer on a delwri queue */
#define _XBF_COMPOUND (1 << 23)/* compound buffer */
+#define _XBF_IN_FLIGHT (1 << 25) /* I/O in flight, for accounting purposes */
typedef unsigned int xfs_buf_flags_t;
@@ -81,7 +83,8 @@
{ _XBF_PAGES, "PAGES" }, \
{ _XBF_KMEM, "KMEM" }, \
{ _XBF_DELWRI_Q, "DELWRI_Q" }, \
- { _XBF_COMPOUND, "COMPOUND" }
+ { _XBF_COMPOUND, "COMPOUND" }, \
+ { _XBF_IN_FLIGHT, "IN_FLIGHT" }
/*
@@ -115,6 +118,8 @@
/* LRU control structures */
struct shrinker bt_shrinker;
struct list_lru bt_lru;
+
+ struct percpu_counter bt_io_count;
} xfs_buftarg_t;
struct xfs_buf;
diff --git a/fs/xfs/xfs_buf_item.c b/fs/xfs/xfs_buf_item.c
index 2e95ad0..0337690 100644
--- a/fs/xfs/xfs_buf_item.c
+++ b/fs/xfs/xfs_buf_item.c
@@ -1081,6 +1081,8 @@
trace_xfs_buf_item_iodone_async(bp, _RET_IP_);
ASSERT(bp->b_iodone != NULL);
+ cfg = xfs_error_get_cfg(mp, XFS_ERR_METADATA, bp->b_error);
+
/*
* If the write was asynchronous then no one will be looking for the
* error. If this is the first failure of this type, clear the error
@@ -1088,13 +1090,12 @@
* async write failure at least once, but we also need to set the buffer
* up to behave correctly now for repeated failures.
*/
- if (!(bp->b_flags & (XBF_STALE|XBF_WRITE_FAIL)) ||
+ if (!(bp->b_flags & (XBF_STALE | XBF_WRITE_FAIL)) ||
bp->b_last_error != bp->b_error) {
- bp->b_flags |= (XBF_WRITE | XBF_ASYNC |
- XBF_DONE | XBF_WRITE_FAIL);
+ bp->b_flags |= (XBF_WRITE | XBF_DONE | XBF_WRITE_FAIL);
bp->b_last_error = bp->b_error;
- bp->b_retries = 0;
- bp->b_first_retry_time = jiffies;
+ if (cfg->retry_timeout && !bp->b_first_retry_time)
+ bp->b_first_retry_time = jiffies;
xfs_buf_ioerror(bp, 0);
xfs_buf_submit(bp);
@@ -1105,7 +1106,6 @@
* Repeated failure on an async write. Take action according to the
* error configuration we have been set up to use.
*/
- cfg = xfs_error_get_cfg(mp, XFS_ERR_METADATA, bp->b_error);
if (cfg->max_retries != XFS_ERR_RETRY_FOREVER &&
++bp->b_retries > cfg->max_retries)
diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index 63dad9e..3b74fa0 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -1415,7 +1415,7 @@
*/
error = -ENOMEM;
bp = xfs_buf_alloc(mp->m_logdev_targp, XFS_BUF_DADDR_NULL,
- BTOBB(log->l_iclog_size), 0);
+ BTOBB(log->l_iclog_size), XBF_NO_IOACCT);
if (!bp)
goto out_free_log;
@@ -1454,7 +1454,8 @@
prev_iclog = iclog;
bp = xfs_buf_get_uncached(mp->m_logdev_targp,
- BTOBB(log->l_iclog_size), 0);
+ BTOBB(log->l_iclog_size),
+ XBF_NO_IOACCT);
if (!bp)
goto out_free_iclog;
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index e39b023..970c19b 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -272,13 +272,15 @@
buf_ops = NULL;
/*
- * Allocate a (locked) buffer to hold the superblock.
- * This will be kept around at all times to optimize
- * access to the superblock.
+ * Allocate a (locked) buffer to hold the superblock. This will be kept
+ * around at all times to optimize access to the superblock. Therefore,
+ * set XBF_NO_IOACCT to make sure it doesn't hold the buftarg count
+ * elevated.
*/
reread:
error = xfs_buf_read_uncached(mp->m_ddev_targp, XFS_SB_DADDR,
- BTOBB(sector_size), 0, &bp, buf_ops);
+ BTOBB(sector_size), XBF_NO_IOACCT, &bp,
+ buf_ops);
if (error) {
if (loud)
xfs_warn(mp, "SB validate failed with error %d.", error);
diff --git a/fs/xfs/xfs_sysfs.c b/fs/xfs/xfs_sysfs.c
index 4c2c550..79cfd3f 100644
--- a/fs/xfs/xfs_sysfs.c
+++ b/fs/xfs/xfs_sysfs.c
@@ -634,6 +634,9 @@
{
struct xfs_error_cfg *cfg;
+ if (error < 0)
+ error = -error;
+
switch (error) {
case EIO:
cfg = &mp->m_error_cfg[error_class][XFS_ERR_EIO];
