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Message-ID: <20121214022323.2969.31644.stgit@perseus.themaw.net>
Date: Fri, 14 Dec 2012 10:23:23 +0800
From: Ian Kent <raven@...maw.net>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: autofs mailing list <autofs@...r.kernel.org>,
Kernel Mailing List <linux-kernel@...r.kernel.org>,
linux-fsdevel <linux-fsdevel@...r.kernel.org>,
Al Viro <viro@...IV.linux.org.uk>
Subject: [PATCH 1/2] autofs4 - dont clear DCACHE_NEED_AUTOMOUNT on rootless
mount
The DCACHE_NEED_AUTOMOUNT flag is cleared on mount and set on expire
for autofs rootless multi-mount dentrys to prevent unnecessary calls
to ->d_automount().
Since DCACHE_MANAGE_TRANSIT is always set on autofs dentrys ->d_managed()
is always called so the check can be done in ->d_manage() without the
need to change the flag. This still avoids unnecessary calls to
->d_automount(), adds negligible overhead and eliminates a seriously
ugly check in the expire code.
Signed-off-by: Ian Kent <raven@...maw.net>
---
fs/autofs4/expire.c | 9 --------
fs/autofs4/root.c | 61 ++++++++++++++++++++++++++++++---------------------
2 files changed, 36 insertions(+), 34 deletions(-)
diff --git a/fs/autofs4/expire.c b/fs/autofs4/expire.c
index 842d000..01443ce 100644
--- a/fs/autofs4/expire.c
+++ b/fs/autofs4/expire.c
@@ -548,15 +548,6 @@ int autofs4_do_expire_multi(struct super_block *sb, struct vfsmount *mnt,
spin_lock(&sbi->fs_lock);
ino->flags &= ~AUTOFS_INF_EXPIRING;
- spin_lock(&dentry->d_lock);
- if (!ret) {
- if ((IS_ROOT(dentry) ||
- (autofs_type_indirect(sbi->type) &&
- IS_ROOT(dentry->d_parent))) &&
- !(dentry->d_flags & DCACHE_NEED_AUTOMOUNT))
- __managed_dentry_set_automount(dentry);
- }
- spin_unlock(&dentry->d_lock);
complete_all(&ino->expire_complete);
spin_unlock(&sbi->fs_lock);
dput(dentry);
diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
index 91b1165..30a6ab66 100644
--- a/fs/autofs4/root.c
+++ b/fs/autofs4/root.c
@@ -355,7 +355,6 @@ static struct vfsmount *autofs4_d_automount(struct path *path)
status = autofs4_mount_wait(dentry);
if (status)
return ERR_PTR(status);
- spin_lock(&sbi->fs_lock);
goto done;
}
@@ -364,8 +363,11 @@ static struct vfsmount *autofs4_d_automount(struct path *path)
* having d_mountpoint() true, so there's no need to call back
* to the daemon.
*/
- if (dentry->d_inode && S_ISLNK(dentry->d_inode->i_mode))
+ if (dentry->d_inode && S_ISLNK(dentry->d_inode->i_mode)) {
+ spin_unlock(&sbi->fs_lock);
goto done;
+ }
+
if (!d_mountpoint(dentry)) {
/*
* It's possible that user space hasn't removed directories
@@ -379,8 +381,10 @@ static struct vfsmount *autofs4_d_automount(struct path *path)
* require user space behave.
*/
if (sbi->version > 4) {
- if (have_submounts(dentry))
+ if (have_submounts(dentry)) {
+ spin_unlock(&sbi->fs_lock);
goto done;
+ }
} else {
spin_lock(&dentry->d_lock);
if (!list_empty(&dentry->d_subdirs)) {
@@ -399,28 +403,8 @@ static struct vfsmount *autofs4_d_automount(struct path *path)
return ERR_PTR(status);
}
}
-done:
- if (!(ino->flags & AUTOFS_INF_EXPIRING)) {
- /*
- * Any needed mounting has been completed and the path
- * updated so clear DCACHE_NEED_AUTOMOUNT so we don't
- * call ->d_automount() on rootless multi-mounts since
- * it can lead to an incorrect ELOOP error return.
- *
- * Only clear DMANAGED_AUTOMOUNT for rootless multi-mounts and
- * symlinks as in all other cases the dentry will be covered by
- * an actual mount so ->d_automount() won't be called during
- * the follow.
- */
- spin_lock(&dentry->d_lock);
- if ((!d_mountpoint(dentry) &&
- !list_empty(&dentry->d_subdirs)) ||
- (dentry->d_inode && S_ISLNK(dentry->d_inode->i_mode)))
- __managed_dentry_clear_automount(dentry);
- spin_unlock(&dentry->d_lock);
- }
spin_unlock(&sbi->fs_lock);
-
+done:
/* Mount succeeded, check if we ended up with a new dentry */
dentry = autofs4_mountpoint_changed(path);
if (!dentry)
@@ -432,6 +416,8 @@ done:
int autofs4_d_manage(struct dentry *dentry, bool rcu_walk)
{
struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
+ struct autofs_info *ino = autofs4_dentry_ino(dentry);
+ int status;
DPRINTK("dentry=%p %.*s",
dentry, dentry->d_name.len, dentry->d_name.name);
@@ -456,7 +442,32 @@ int autofs4_d_manage(struct dentry *dentry, bool rcu_walk)
* This dentry may be under construction so wait on mount
* completion.
*/
- return autofs4_mount_wait(dentry);
+ status = autofs4_mount_wait(dentry);
+ if (status)
+ return status;
+
+ spin_lock(&sbi->fs_lock);
+ /*
+ * If the dentry has been selected for expire while we slept
+ * on the lock then it might go away. We'll deal with that in
+ * ->d_automount() and wait on a new mount if the expire
+ * succeeds or return here if it doesn't (since there's no
+ * mount to follow with a rootless multi-mount).
+ */
+ if (!(ino->flags & AUTOFS_INF_EXPIRING)) {
+ /*
+ * Any needed mounting has been completed and the path
+ * updated so check if this is a rootless multi-mount so
+ * we can avoid needless calls ->d_automount() and avoid
+ * an incorrect ELOOP error return.
+ */
+ if ((!d_mountpoint(dentry) && !simple_empty(dentry)) ||
+ (dentry->d_inode && S_ISLNK(dentry->d_inode->i_mode)))
+ status = -EISDIR;
+ }
+ spin_unlock(&sbi->fs_lock);
+
+ return status;
}
/* Lookups in the root directory */
--
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