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Subject[PATCH 2/4] autofs4 - fix rootless multi-mount race
Date
When there is no mount at the base of a mount tree (rootless multi-mount)
there is a small amount of time when both DCACHE_MANAGE_TRANSIT and
DCACHE_NEED_AUTOMOUNT are clear. This occassionally alows a process
to pass instead of bock leading to an incorrect fail return. Keeping
the DCACHE_MANAGE_TRANSIT set all the time resolves the problem.

Signed-off-by: Ian Kent <raven@themaw.net>
---

fs/autofs4/expire.c | 13 ++-----------
fs/autofs4/root.c | 20 ++++----------------
2 files changed, 6 insertions(+), 27 deletions(-)

diff --git a/fs/autofs4/expire.c b/fs/autofs4/expire.c
index f43100b..c896dd6 100644
--- a/fs/autofs4/expire.c
+++ b/fs/autofs4/expire.c
@@ -294,7 +294,6 @@ struct dentry *autofs4_expire_direct(struct super_block *sb,
spin_unlock(&sbi->fs_lock);
return NULL;
}
- managed_dentry_set_transit(root);
if (!autofs4_direct_busy(mnt, root, timeout, do_now)) {
struct autofs_info *ino = autofs4_dentry_ino(root);
ino->flags |= AUTOFS_INF_EXPIRING;
@@ -302,7 +301,6 @@ struct dentry *autofs4_expire_direct(struct super_block *sb,
spin_unlock(&sbi->fs_lock);
return root;
}
- managed_dentry_clear_transit(root);
spin_unlock(&sbi->fs_lock);
dput(root);

@@ -341,8 +339,7 @@ struct dentry *autofs4_expire_indirect(struct super_block *sb,
ino = autofs4_dentry_ino(dentry);
/* No point expiring a pending mount */
if (ino->flags & AUTOFS_INF_PENDING)
- goto cont;
- managed_dentry_set_transit(dentry);
+ goto next;

/*
* Case 1: (i) indirect mount or top level pseudo direct mount
@@ -402,8 +399,6 @@ struct dentry *autofs4_expire_indirect(struct super_block *sb,
}
}
next:
- managed_dentry_clear_transit(dentry);
-cont:
spin_unlock(&sbi->fs_lock);
}
return NULL;
@@ -484,8 +479,6 @@ int autofs4_expire_run(struct super_block *sb,
spin_lock(&sbi->fs_lock);
ino = autofs4_dentry_ino(dentry);
ino->flags &= ~AUTOFS_INF_EXPIRING;
- if (!d_unhashed(dentry))
- managed_dentry_clear_transit(dentry);
complete_all(&ino->expire_complete);
spin_unlock(&sbi->fs_lock);

@@ -513,9 +506,7 @@ 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)
- __managed_dentry_clear_transit(dentry);
- else {
+ if (!ret) {
if ((IS_ROOT(dentry) ||
(autofs_type_indirect(sbi->type) &&
IS_ROOT(dentry->d_parent))) &&
diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
index 014e7ab..ad11a44 100644
--- a/fs/autofs4/root.c
+++ b/fs/autofs4/root.c
@@ -338,18 +338,6 @@ static struct vfsmount *autofs4_d_automount(struct path *path)
DPRINTK("dentry=%p %.*s",
dentry, dentry->d_name.len, dentry->d_name.name);

- /*
- * Someone may have manually umounted this or it was a submount
- * that has gone away.
- */
- spin_lock(&dentry->d_lock);
- if (!d_mountpoint(dentry) && list_empty(&dentry->d_subdirs)) {
- if (!(dentry->d_flags & DCACHE_MANAGE_TRANSIT) &&
- (dentry->d_flags & DCACHE_NEED_AUTOMOUNT))
- __managed_dentry_set_transit(path->dentry);
- }
- spin_unlock(&dentry->d_lock);
-
/* The daemon never triggers a mount. */
if (autofs4_oz_mode(sbi))
return NULL;
@@ -418,12 +406,12 @@ static struct vfsmount *autofs4_d_automount(struct path *path)
done:
if (!(ino->flags & AUTOFS_INF_EXPIRING)) {
/*
- * Any needed mounting has been completed and the path updated
- * so turn this into a normal dentry so we don't continually
- * call ->d_automount() and ->d_manage().
+ * 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.
*/
spin_lock(&dentry->d_lock);
- __managed_dentry_clear_transit(dentry);
/*
* Only clear DMANAGED_AUTOMOUNT for rootless multi-mounts and
* symlinks as in all other cases the dentry will be covered by


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