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-rw-r--r--fs/xfs/linux-2.6/xfs_sync.c84
-rw-r--r--fs/xfs/xfs_iget.c47
-rw-r--r--fs/xfs/xfs_inode.c52
3 files changed, 141 insertions, 42 deletions
diff --git a/fs/xfs/linux-2.6/xfs_sync.c b/fs/xfs/linux-2.6/xfs_sync.c
index afb0d7c..fd38682 100644
--- a/fs/xfs/linux-2.6/xfs_sync.c
+++ b/fs/xfs/linux-2.6/xfs_sync.c
@@ -53,14 +53,30 @@ xfs_inode_ag_walk_grab(
{
struct inode *inode = VFS_I(ip);
+ ASSERT(rcu_read_lock_held());
+
+ /*
+ * check for stale RCU freed inode
+ *
+ * If the inode has been reallocated, it doesn't matter if it's not in
+ * the AG we are walking - we are walking for writeback, so if it
+ * passes all the "valid inode" checks and is dirty, then we'll write
+ * it back anyway. If it has been reallocated and still being
+ * initialised, the XFS_INEW check below will catch it.
+ */
+ spin_lock(&ip->i_flags_lock);
+ if (!ip->i_ino)
+ goto out_unlock_noent;
+
+ /* avoid new or reclaimable inodes. Leave for reclaim code to flush */
+ if (__xfs_iflags_test(ip, XFS_INEW | XFS_IRECLAIMABLE | XFS_IRECLAIM))
+ goto out_unlock_noent;
+ spin_unlock(&ip->i_flags_lock);
+
/* nothing to sync during shutdown */
if (XFS_FORCED_SHUTDOWN(ip->i_mount))
return EFSCORRUPTED;
- /* avoid new or reclaimable inodes. Leave for reclaim code to flush */
- if (xfs_iflags_test(ip, XFS_INEW | XFS_IRECLAIMABLE | XFS_IRECLAIM))
- return ENOENT;
-
/* If we can't grab the inode, it must on it's way to reclaim. */
if (!igrab(inode))
return ENOENT;
@@ -72,6 +88,10 @@ xfs_inode_ag_walk_grab(
/* inode is valid */
return 0;
+
+out_unlock_noent:
+ spin_unlock(&ip->i_flags_lock);
+ return ENOENT;
}
STATIC int
@@ -98,12 +118,12 @@ restart:
int error = 0;
int i;
- read_lock(&pag->pag_ici_lock);
+ rcu_read_lock();
nr_found = radix_tree_gang_lookup(&pag->pag_ici_root,
(void **)batch, first_index,
XFS_LOOKUP_BATCH);
if (!nr_found) {
- read_unlock(&pag->pag_ici_lock);
+ rcu_read_unlock();
break;
}
@@ -118,18 +138,26 @@ restart:
batch[i] = NULL;
/*
- * Update the index for the next lookup. Catch overflows
- * into the next AG range which can occur if we have inodes
- * in the last block of the AG and we are currently
- * pointing to the last inode.
+ * Update the index for the next lookup. Catch
+ * overflows into the next AG range which can occur if
+ * we have inodes in the last block of the AG and we
+ * are currently pointing to the last inode.
+ *
+ * Because we may see inodes that are from the wrong AG
+ * due to RCU freeing and reallocation, only update the
+ * index if it lies in this AG. It was a race that lead
+ * us to see this inode, so another lookup from the
+ * same index will not find it again.
*/
+ if (XFS_INO_TO_AGNO(mp, ip->i_ino) != pag->pag_agno)
+ continue;
first_index = XFS_INO_TO_AGINO(mp, ip->i_ino + 1);
if (first_index < XFS_INO_TO_AGINO(mp, ip->i_ino))
done = 1;
}
/* unlock now we've grabbed the inodes. */
- read_unlock(&pag->pag_ici_lock);
+ rcu_read_unlock();
for (i = 0; i < nr_found; i++) {
if (!batch[i])
@@ -639,9 +667,14 @@ xfs_reclaim_inode_grab(
struct xfs_inode *ip,
int flags)
{
+ ASSERT(rcu_read_lock_held());
+
+ /* quick check for stale RCU freed inode */
+ if (!ip->i_ino)
+ return 1;
/*
- * do some unlocked checks first to avoid unnecceary lock traffic.
+ * do some unlocked checks first to avoid unnecessary lock traffic.
* The first is a flush lock check, the second is a already in reclaim
* check. Only do these checks if we are not going to block on locks.
*/
@@ -654,11 +687,16 @@ xfs_reclaim_inode_grab(
* The radix tree lock here protects a thread in xfs_iget from racing
* with us starting reclaim on the inode. Once we have the
* XFS_IRECLAIM flag set it will not touch us.
+ *
+ * Due to RCU lookup, we may find inodes that have been freed and only
+ * have XFS_IRECLAIM set. Indeed, we may see reallocated inodes that
+ * aren't candidates for reclaim at all, so we must check the
+ * XFS_IRECLAIMABLE is set first before proceeding to reclaim.
*/
spin_lock(&ip->i_flags_lock);
- ASSERT_ALWAYS(__xfs_iflags_test(ip, XFS_IRECLAIMABLE));
- if (__xfs_iflags_test(ip, XFS_IRECLAIM)) {
- /* ignore as it is already under reclaim */
+ if (!__xfs_iflags_test(ip, XFS_IRECLAIMABLE) ||
+ __xfs_iflags_test(ip, XFS_IRECLAIM)) {
+ /* not a reclaim candidate. */
spin_unlock(&ip->i_flags_lock);
return 1;
}
@@ -864,14 +902,14 @@ restart:
struct xfs_inode *batch[XFS_LOOKUP_BATCH];
int i;
- write_lock(&pag->pag_ici_lock);
+ rcu_read_lock();
nr_found = radix_tree_gang_lookup_tag(
&pag->pag_ici_root,
(void **)batch, first_index,
XFS_LOOKUP_BATCH,
XFS_ICI_RECLAIM_TAG);
if (!nr_found) {
- write_unlock(&pag->pag_ici_lock);
+ rcu_read_unlock();
break;
}
@@ -891,14 +929,24 @@ restart:
* occur if we have inodes in the last block of
* the AG and we are currently pointing to the
* last inode.
+ *
+ * Because we may see inodes that are from the
+ * wrong AG due to RCU freeing and
+ * reallocation, only update the index if it
+ * lies in this AG. It was a race that lead us
+ * to see this inode, so another lookup from
+ * the same index will not find it again.
*/
+ if (XFS_INO_TO_AGNO(mp, ip->i_ino) !=
+ pag->pag_agno)
+ continue;
first_index = XFS_INO_TO_AGINO(mp, ip->i_ino + 1);
if (first_index < XFS_INO_TO_AGINO(mp, ip->i_ino))
done = 1;
}
/* unlock now we've grabbed the inodes. */
- write_unlock(&pag->pag_ici_lock);
+ rcu_read_unlock();
for (i = 0; i < nr_found; i++) {
if (!batch[i])
diff --git a/fs/xfs/xfs_iget.c b/fs/xfs/xfs_iget.c
index 9fae475..04ed09b 100644
--- a/fs/xfs/xfs_iget.c
+++ b/fs/xfs/xfs_iget.c
@@ -80,6 +80,7 @@ xfs_inode_alloc(
ASSERT(atomic_read(&ip->i_pincount) == 0);
ASSERT(!spin_is_locked(&ip->i_flags_lock));
ASSERT(completion_done(&ip->i_flush));
+ ASSERT(ip->i_ino == 0);
mrlock_init(&ip->i_iolock, MRLOCK_BARRIER, "xfsio", ip->i_ino);
lockdep_set_class_and_name(&ip->i_iolock.mr_lock,
@@ -98,9 +99,6 @@ xfs_inode_alloc(
ip->i_size = 0;
ip->i_new_size = 0;
- /* prevent anyone from using this yet */
- VFS_I(ip)->i_state = I_NEW;
-
return ip;
}
@@ -159,6 +157,16 @@ xfs_inode_free(
ASSERT(!spin_is_locked(&ip->i_flags_lock));
ASSERT(completion_done(&ip->i_flush));
+ /*
+ * Because we use RCU freeing we need to ensure the inode always
+ * appears to be reclaimed with an invalid inode number when in the
+ * free state. The ip->i_flags_lock provides the barrier against lookup
+ * races.
+ */
+ spin_lock(&ip->i_flags_lock);
+ ip->i_flags = XFS_IRECLAIM;
+ ip->i_ino = 0;
+ spin_unlock(&ip->i_flags_lock);
call_rcu((struct rcu_head *)&VFS_I(ip)->i_dentry, __xfs_inode_free);
}
@@ -169,14 +177,29 @@ static int
xfs_iget_cache_hit(
struct xfs_perag *pag,
struct xfs_inode *ip,
+ xfs_ino_t ino,
int flags,
- int lock_flags) __releases(pag->pag_ici_lock)
+ int lock_flags) __releases(RCU)
{
struct inode *inode = VFS_I(ip);
struct xfs_mount *mp = ip->i_mount;
int error;
+ /*
+ * check for re-use of an inode within an RCU grace period due to the
+ * radix tree nodes not being updated yet. We monitor for this by
+ * setting the inode number to zero before freeing the inode structure.
+ * If the inode has been reallocated and set up, then the inode number
+ * will not match, so check for that, too.
+ */
spin_lock(&ip->i_flags_lock);
+ if (ip->i_ino != ino) {
+ trace_xfs_iget_skip(ip);
+ XFS_STATS_INC(xs_ig_frecycle);
+ error = EAGAIN;
+ goto out_error;
+ }
+
/*
* If we are racing with another cache hit that is currently
@@ -219,7 +242,7 @@ xfs_iget_cache_hit(
ip->i_flags |= XFS_IRECLAIM;
spin_unlock(&ip->i_flags_lock);
- read_unlock(&pag->pag_ici_lock);
+ rcu_read_unlock();
error = -inode_init_always(mp->m_super, inode);
if (error) {
@@ -227,7 +250,7 @@ xfs_iget_cache_hit(
* Re-initializing the inode failed, and we are in deep
* trouble. Try to re-add it to the reclaim list.
*/
- read_lock(&pag->pag_ici_lock);
+ rcu_read_lock();
spin_lock(&ip->i_flags_lock);
ip->i_flags &= ~XFS_INEW;
@@ -261,7 +284,7 @@ xfs_iget_cache_hit(
/* We've got a live one. */
spin_unlock(&ip->i_flags_lock);
- read_unlock(&pag->pag_ici_lock);
+ rcu_read_unlock();
trace_xfs_iget_hit(ip);
}
@@ -275,7 +298,7 @@ xfs_iget_cache_hit(
out_error:
spin_unlock(&ip->i_flags_lock);
- read_unlock(&pag->pag_ici_lock);
+ rcu_read_unlock();
return error;
}
@@ -397,7 +420,7 @@ xfs_iget(
xfs_agino_t agino;
/* reject inode numbers outside existing AGs */
- if (XFS_INO_TO_AGNO(mp, ino) >= mp->m_sb.sb_agcount)
+ if (!ino || XFS_INO_TO_AGNO(mp, ino) >= mp->m_sb.sb_agcount)
return EINVAL;
/* get the perag structure and ensure that it's inode capable */
@@ -406,15 +429,15 @@ xfs_iget(
again:
error = 0;
- read_lock(&pag->pag_ici_lock);
+ rcu_read_lock();
ip = radix_tree_lookup(&pag->pag_ici_root, agino);
if (ip) {
- error = xfs_iget_cache_hit(pag, ip, flags, lock_flags);
+ error = xfs_iget_cache_hit(pag, ip, ino, flags, lock_flags);
if (error)
goto out_error_or_again;
} else {
- read_unlock(&pag->pag_ici_lock);
+ rcu_read_unlock();
XFS_STATS_INC(xs_ig_missed);
error = xfs_iget_cache_miss(mp, pag, tp, ino, &ip,
diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 108c7a0..43ffd90 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -2000,17 +2000,33 @@ xfs_ifree_cluster(
*/
for (i = 0; i < ninodes; i++) {
retry:
- read_lock(&pag->pag_ici_lock);
+ rcu_read_lock();
ip = radix_tree_lookup(&pag->pag_ici_root,
XFS_INO_TO_AGINO(mp, (inum + i)));
- /* Inode not in memory or stale, nothing to do */
- if (!ip || xfs_iflags_test(ip, XFS_ISTALE)) {
- read_unlock(&pag->pag_ici_lock);
+ /* Inode not in memory, nothing to do */
+ if (!ip) {
+ rcu_read_unlock();
continue;
}
/*
+ * because this is an RCU protected lookup, we could
+ * find a recently freed or even reallocated inode
+ * during the lookup. We need to check under the
+ * i_flags_lock for a valid inode here. Skip it if it
+ * is not valid, the wrong inode or stale.
+ */
+ spin_lock(&ip->i_flags_lock);
+ if (ip->i_ino != inum + i ||
+ __xfs_iflags_test(ip, XFS_ISTALE)) {
+ spin_unlock(&ip->i_flags_lock);
+ rcu_read_unlock();
+ continue;
+ }
+ spin_unlock(&ip->i_flags_lock);
+
+ /*
* Don't try to lock/unlock the current inode, but we
* _cannot_ skip the other inodes that we did not find
* in the list attached to the buffer and are not
@@ -2019,11 +2035,11 @@ retry:
*/
if (ip != free_ip &&
!xfs_ilock_nowait(ip, XFS_ILOCK_EXCL)) {
- read_unlock(&pag->pag_ici_lock);
+ rcu_read_unlock();
delay(1);
goto retry;
}
- read_unlock(&pag->pag_ici_lock);
+ rcu_read_unlock();
xfs_iflock(ip);
xfs_iflags_set(ip, XFS_ISTALE);
@@ -2629,7 +2645,7 @@ xfs_iflush_cluster(
mask = ~(((XFS_INODE_CLUSTER_SIZE(mp) >> mp->m_sb.sb_inodelog)) - 1);
first_index = XFS_INO_TO_AGINO(mp, ip->i_ino) & mask;
- read_lock(&pag->pag_ici_lock);
+ rcu_read_lock();
/* really need a gang lookup range call here */
nr_found = radix_tree_gang_lookup(&pag->pag_ici_root, (void**)ilist,
first_index, inodes_per_cluster);
@@ -2640,9 +2656,21 @@ xfs_iflush_cluster(
iq = ilist[i];
if (iq == ip)
continue;
- /* if the inode lies outside this cluster, we're done. */
- if ((XFS_INO_TO_AGINO(mp, iq->i_ino) & mask) != first_index)
- break;
+
+ /*
+ * because this is an RCU protected lookup, we could find a
+ * recently freed or even reallocated inode during the lookup.
+ * We need to check under the i_flags_lock for a valid inode
+ * here. Skip it if it is not valid or the wrong inode.
+ */
+ spin_lock(&ip->i_flags_lock);
+ if (!ip->i_ino ||
+ (XFS_INO_TO_AGINO(mp, iq->i_ino) & mask) != first_index) {
+ spin_unlock(&ip->i_flags_lock);
+ continue;
+ }
+ spin_unlock(&ip->i_flags_lock);
+
/*
* Do an un-protected check to see if the inode is dirty and
* is a candidate for flushing. These checks will be repeated
@@ -2692,7 +2720,7 @@ xfs_iflush_cluster(
}
out_free:
- read_unlock(&pag->pag_ici_lock);
+ rcu_read_unlock();
kmem_free(ilist);
out_put:
xfs_perag_put(pag);
@@ -2704,7 +2732,7 @@ cluster_corrupt_out:
* Corruption detected in the clustering loop. Invalidate the
* inode buffer and shut down the filesystem.
*/
- read_unlock(&pag->pag_ici_lock);
+ rcu_read_unlock();
/*
* Clean up the buffer. If it was B_DELWRI, just release it --
* brelse can handle it with no problems. If not, shut down the
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