From ef16cc5909c907586f4eba5455e183fd319637c8 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Mon, 13 Oct 2014 15:52:22 -0700 Subject: [PATCH] autofs4: d_manage() should return -EISDIR when appropriate in rcu-walk mode. 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. Signed-off-by: NeilBrown Reviewed-by: Ian Kent Tested-by: Ian Kent Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- 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..d76d083f2f06 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 = ACCESS_ONCE(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); /* -- 2.30.2