If rcu-walk mode we don't *have* to return -EISDIR for non-mount-traps
as we will simply drop into REF-walk and handling DCACHE_NEED_AUTOMOUNT
dentrys the slow way. But it is better if we do when possible.
In 'oz_mode', use the same condition as ref-walk: if not a mountpoint,
then it must be -EISDIR.
In regular mode there are most tests needed. Most of them can be
performed without taking any spinlocks.
If we find a directory that isn't obviously empty, and isn't mounted
on, we need to call 'simple_empty()' which does take a spinlock.
If this turned out to hurt performance, some other approach could
be found to signal when a directory is known to be empty.
Reviewed-by: Ian Kent <raven@xxxxxxxxxx>
Tested-by: Ian Kent <raven@xxxxxxxxxx>
Signed-off-by: NeilBrown <neilb@xxxxxxx>
---
fs/autofs4/root.c | 26 ++++++++++++++++++++------
1 file changed, 20 insertions(+), 6 deletions(-)
diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
index 2296c8301b66..71e4413d65c8 100644
--- a/fs/autofs4/root.c
+++ b/fs/autofs4/root.c
@@ -433,8 +433,6 @@ static int autofs4_d_manage(struct dentry *dentry, bool rcu_walk)
/* The daemon never waits. */
if (autofs4_oz_mode(sbi)) {
- if (rcu_walk)
- return 0;
if (!d_mountpoint(dentry))
return -EISDIR;
return 0;
@@ -452,12 +450,28 @@ static int autofs4_d_manage(struct dentry *dentry, bool rcu_walk)
if (status)
return status;
- if (rcu_walk)
- /* it is always safe to return 0 as the worst that
- * will happen is we retry in REF-walk mode.
- * Better than always taking a lock.
+ if (rcu_walk) {
+ /* We don't need fs_lock in rcu_walk mode,
+ * just testing 'AUTOFS_INFO_NO_RCU' is enough.
+ * simple_empty() takes a spinlock, so leave it
+ * to last.
+ * We only return -EISDIR when certain this isn't
+ * a mount-trap.
*/
+ struct inode *inode;
+ if (ino->flags & (AUTOFS_INF_EXPIRING | AUTOFS_INF_NO_RCU))
+ return 0;
+ if (d_mountpoint(dentry))
+ return 0;
+ inode = rcu_dereference(dentry->d_inode);
+ if (inode && S_ISLNK(inode->i_mode))
+ return -EISDIR;
+ if (list_empty(&dentry->d_subdirs))
+ return 0;
+ if (!simple_empty(dentry))
+ return -EISDIR;
return 0;
+ }
spin_lock(&sbi->fs_lock);
/*
--
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