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-rw-r--r--fs/autofs4/autofs_i.h6
-rw-r--r--fs/autofs4/dev-ioctl.c2
-rw-r--r--fs/autofs4/expire.c210
-rw-r--r--fs/autofs4/root.c62
4 files changed, 178 insertions, 102 deletions
diff --git a/fs/autofs4/autofs_i.h b/fs/autofs4/autofs_i.h
index 9e359fb20c0a..8e98cf954bab 100644
--- a/fs/autofs4/autofs_i.h
+++ b/fs/autofs4/autofs_i.h
@@ -79,6 +79,10 @@ struct autofs_info {
};
#define AUTOFS_INF_EXPIRING (1<<0) /* dentry is in the process of expiring */
+#define AUTOFS_INF_NO_RCU (1<<1) /* the dentry is being considered
+ * for expiry, so RCU_walk is
+ * not permitted
+ */
#define AUTOFS_INF_PENDING (1<<2) /* dentry pending mount */
struct autofs_wait_queue {
@@ -148,7 +152,7 @@ void autofs4_free_ino(struct autofs_info *);
/* Expiration */
int is_autofs4_dentry(struct dentry *);
-int autofs4_expire_wait(struct dentry *dentry);
+int autofs4_expire_wait(struct dentry *dentry, int rcu_walk);
int autofs4_expire_run(struct super_block *, struct vfsmount *,
struct autofs_sb_info *,
struct autofs_packet_expire __user *);
diff --git a/fs/autofs4/dev-ioctl.c b/fs/autofs4/dev-ioctl.c
index 5b570b6efa28..aaf96cb25452 100644
--- a/fs/autofs4/dev-ioctl.c
+++ b/fs/autofs4/dev-ioctl.c
@@ -450,7 +450,7 @@ static int autofs_dev_ioctl_requester(struct file *fp,
ino = autofs4_dentry_ino(path.dentry);
if (ino) {
err = 0;
- autofs4_expire_wait(path.dentry);
+ autofs4_expire_wait(path.dentry, 0);
spin_lock(&sbi->fs_lock);
param->requester.uid = from_kuid_munged(current_user_ns(), ino->uid);
param->requester.gid = from_kgid_munged(current_user_ns(), ino->gid);
diff --git a/fs/autofs4/expire.c b/fs/autofs4/expire.c
index 8fa3895cda02..683a5b9ce22a 100644
--- a/fs/autofs4/expire.c
+++ b/fs/autofs4/expire.c
@@ -30,12 +30,6 @@ static inline int autofs4_can_expire(struct dentry *dentry,
/* Too young to die */
if (!timeout || time_after(ino->last_used + timeout, now))
return 0;
-
- /* update last_used here :-
- - obviously makes sense if it is in use now
- - less obviously, prevents rapid-fire expire
- attempts if expire fails the first time */
- ino->last_used = now;
}
return 1;
}
@@ -327,10 +321,19 @@ struct dentry *autofs4_expire_direct(struct super_block *sb,
if (ino->flags & AUTOFS_INF_PENDING)
goto out;
if (!autofs4_direct_busy(mnt, root, timeout, do_now)) {
- ino->flags |= AUTOFS_INF_EXPIRING;
- init_completion(&ino->expire_complete);
+ ino->flags |= AUTOFS_INF_NO_RCU;
spin_unlock(&sbi->fs_lock);
- return root;
+ synchronize_rcu();
+ spin_lock(&sbi->fs_lock);
+ if (!autofs4_direct_busy(mnt, root, timeout, do_now)) {
+ ino->flags |= AUTOFS_INF_EXPIRING;
+ smp_mb();
+ ino->flags &= ~AUTOFS_INF_NO_RCU;
+ init_completion(&ino->expire_complete);
+ spin_unlock(&sbi->fs_lock);
+ return root;
+ }
+ ino->flags &= ~AUTOFS_INF_NO_RCU;
}
out:
spin_unlock(&sbi->fs_lock);
@@ -339,6 +342,89 @@ out:
return NULL;
}
+/* Check if 'dentry' should expire, or return a nearby
+ * dentry that is suitable.
+ * If returned dentry is different from arg dentry,
+ * then a dget() reference was taken, else not.
+ */
+static struct dentry *should_expire(struct dentry *dentry,
+ struct vfsmount *mnt,
+ unsigned long timeout,
+ int how)
+{
+ int do_now = how & AUTOFS_EXP_IMMEDIATE;
+ int exp_leaves = how & AUTOFS_EXP_LEAVES;
+ struct autofs_info *ino = autofs4_dentry_ino(dentry);
+ unsigned int ino_count;
+
+ /* No point expiring a pending mount */
+ if (ino->flags & AUTOFS_INF_PENDING)
+ return NULL;
+
+ /*
+ * Case 1: (i) indirect mount or top level pseudo direct mount
+ * (autofs-4.1).
+ * (ii) indirect mount with offset mount, check the "/"
+ * offset (autofs-5.0+).
+ */
+ if (d_mountpoint(dentry)) {
+ DPRINTK("checking mountpoint %p %.*s",
+ dentry, (int)dentry->d_name.len, dentry->d_name.name);
+
+ /* Can we umount this guy */
+ if (autofs4_mount_busy(mnt, dentry))
+ return NULL;
+
+ /* Can we expire this guy */
+ if (autofs4_can_expire(dentry, timeout, do_now))
+ return dentry;
+ return NULL;
+ }
+
+ if (dentry->d_inode && S_ISLNK(dentry->d_inode->i_mode)) {
+ DPRINTK("checking symlink %p %.*s",
+ dentry, (int)dentry->d_name.len, dentry->d_name.name);
+ /*
+ * A symlink can't be "busy" in the usual sense so
+ * just check last used for expire timeout.
+ */
+ if (autofs4_can_expire(dentry, timeout, do_now))
+ return dentry;
+ return NULL;
+ }
+
+ if (simple_empty(dentry))
+ return NULL;
+
+ /* Case 2: tree mount, expire iff entire tree is not busy */
+ if (!exp_leaves) {
+ /* Path walk currently on this dentry? */
+ ino_count = atomic_read(&ino->count) + 1;
+ if (d_count(dentry) > ino_count)
+ return NULL;
+
+ if (!autofs4_tree_busy(mnt, dentry, timeout, do_now))
+ return dentry;
+ /*
+ * Case 3: pseudo direct mount, expire individual leaves
+ * (autofs-4.1).
+ */
+ } else {
+ /* Path walk currently on this dentry? */
+ struct dentry *expired;
+ ino_count = atomic_read(&ino->count) + 1;
+ if (d_count(dentry) > ino_count)
+ return NULL;
+
+ expired = autofs4_check_leaves(mnt, dentry, timeout, do_now);
+ if (expired) {
+ if (expired == dentry)
+ dput(dentry);
+ return expired;
+ }
+ }
+ return NULL;
+}
/*
* Find an eligible tree to time-out
* A tree is eligible if :-
@@ -353,11 +439,8 @@ struct dentry *autofs4_expire_indirect(struct super_block *sb,
unsigned long timeout;
struct dentry *root = sb->s_root;
struct dentry *dentry;
- struct dentry *expired = NULL;
- int do_now = how & AUTOFS_EXP_IMMEDIATE;
- int exp_leaves = how & AUTOFS_EXP_LEAVES;
+ struct dentry *expired;
struct autofs_info *ino;
- unsigned int ino_count;
if (!root)
return NULL;
@@ -369,77 +452,28 @@ struct dentry *autofs4_expire_indirect(struct super_block *sb,
while ((dentry = get_next_positive_subdir(dentry, root))) {
spin_lock(&sbi->fs_lock);
ino = autofs4_dentry_ino(dentry);
- /* No point expiring a pending mount */
- if (ino->flags & AUTOFS_INF_PENDING)
- goto next;
-
- /*
- * Case 1: (i) indirect mount or top level pseudo direct mount
- * (autofs-4.1).
- * (ii) indirect mount with offset mount, check the "/"
- * offset (autofs-5.0+).
- */
- if (d_mountpoint(dentry)) {
- DPRINTK("checking mountpoint %p %.*s",
- dentry, (int)dentry->d_name.len, dentry->d_name.name);
-
- /* Can we umount this guy */
- if (autofs4_mount_busy(mnt, dentry))
- goto next;
-
- /* Can we expire this guy */
- if (autofs4_can_expire(dentry, timeout, do_now)) {
- expired = dentry;
- goto found;
- }
- goto next;
+ if (ino->flags & AUTOFS_INF_NO_RCU)
+ expired = NULL;
+ else
+ expired = should_expire(dentry, mnt, timeout, how);
+ if (!expired) {
+ spin_unlock(&sbi->fs_lock);
+ continue;
}
-
- if (dentry->d_inode && S_ISLNK(dentry->d_inode->i_mode)) {
- DPRINTK("checking symlink %p %.*s",
- dentry, (int)dentry->d_name.len, dentry->d_name.name);
- /*
- * A symlink can't be "busy" in the usual sense so
- * just check last used for expire timeout.
- */
- if (autofs4_can_expire(dentry, timeout, do_now)) {
- expired = dentry;
- goto found;
- }
- goto next;
- }
-
- if (simple_empty(dentry))
- goto next;
-
- /* Case 2: tree mount, expire iff entire tree is not busy */
- if (!exp_leaves) {
- /* Path walk currently on this dentry? */
- ino_count = atomic_read(&ino->count) + 1;
- if (d_count(dentry) > ino_count)
- goto next;
-
- if (!autofs4_tree_busy(mnt, dentry, timeout, do_now)) {
- expired = dentry;
- goto found;
- }
- /*
- * Case 3: pseudo direct mount, expire individual leaves
- * (autofs-4.1).
- */
- } else {
- /* Path walk currently on this dentry? */
- ino_count = atomic_read(&ino->count) + 1;
- if (d_count(dentry) > ino_count)
- goto next;
-
- expired = autofs4_check_leaves(mnt, dentry, timeout, do_now);
- if (expired) {
+ ino = autofs4_dentry_ino(expired);
+ ino->flags |= AUTOFS_INF_NO_RCU;
+ spin_unlock(&sbi->fs_lock);
+ synchronize_rcu();
+ spin_lock(&sbi->fs_lock);
+ if (should_expire(expired, mnt, timeout, how)) {
+ if (expired != dentry)
dput(dentry);
- goto found;
- }
+ goto found;
}
-next:
+
+ ino->flags &= ~AUTOFS_INF_NO_RCU;
+ if (expired != dentry)
+ dput(expired);
spin_unlock(&sbi->fs_lock);
}
return NULL;
@@ -447,8 +481,9 @@ next:
found:
DPRINTK("returning %p %.*s",
expired, (int)expired->d_name.len, expired->d_name.name);
- ino = autofs4_dentry_ino(expired);
ino->flags |= AUTOFS_INF_EXPIRING;
+ smp_mb();
+ ino->flags &= ~AUTOFS_INF_NO_RCU;
init_completion(&ino->expire_complete);
spin_unlock(&sbi->fs_lock);
spin_lock(&sbi->lookup_lock);
@@ -461,13 +496,18 @@ found:
return expired;
}
-int autofs4_expire_wait(struct dentry *dentry)
+int autofs4_expire_wait(struct dentry *dentry, int rcu_walk)
{
struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
struct autofs_info *ino = autofs4_dentry_ino(dentry);
int status;
/* Block on any pending expire */
+ if (!(ino->flags & (AUTOFS_INF_EXPIRING | AUTOFS_INF_NO_RCU)))
+ return 0;
+ if (rcu_walk)
+ return -ECHILD;
+
spin_lock(&sbi->fs_lock);
if (ino->flags & AUTOFS_INF_EXPIRING) {
spin_unlock(&sbi->fs_lock);
@@ -519,6 +559,8 @@ int autofs4_expire_run(struct super_block *sb,
spin_lock(&sbi->fs_lock);
ino = autofs4_dentry_ino(dentry);
+ /* avoid rapid-fire expire attempts if expiry fails */
+ ino->last_used = now;
ino->flags &= ~AUTOFS_INF_EXPIRING;
complete_all(&ino->expire_complete);
spin_unlock(&sbi->fs_lock);
@@ -545,6 +587,8 @@ int autofs4_do_expire_multi(struct super_block *sb, struct vfsmount *mnt,
ret = autofs4_wait(sbi, dentry, NFY_EXPIRE);
spin_lock(&sbi->fs_lock);
+ /* avoid rapid-fire expire attempts if expiry fails */
+ ino->last_used = now;
ino->flags &= ~AUTOFS_INF_EXPIRING;
complete_all(&ino->expire_complete);
spin_unlock(&sbi->fs_lock);
diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
index cdb25ebccc4c..d76d083f2f06 100644
--- a/fs/autofs4/root.c
+++ b/fs/autofs4/root.c
@@ -210,7 +210,8 @@ next:
return NULL;
}
-static struct dentry *autofs4_lookup_expiring(struct dentry *dentry)
+static struct dentry *autofs4_lookup_expiring(struct dentry *dentry,
+ bool rcu_walk)
{
struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
struct dentry *parent = dentry->d_parent;
@@ -229,6 +230,11 @@ static struct dentry *autofs4_lookup_expiring(struct dentry *dentry)
struct dentry *expiring;
struct qstr *qstr;
+ if (rcu_walk) {
+ spin_unlock(&sbi->lookup_lock);
+ return ERR_PTR(-ECHILD);
+ }
+
ino = list_entry(p, struct autofs_info, expiring);
expiring = ino->dentry;
@@ -264,13 +270,15 @@ next:
return NULL;
}
-static int autofs4_mount_wait(struct dentry *dentry)
+static int autofs4_mount_wait(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 = 0;
if (ino->flags & AUTOFS_INF_PENDING) {
+ if (rcu_walk)
+ return -ECHILD;
DPRINTK("waiting for mount name=%.*s",
dentry->d_name.len, dentry->d_name.name);
status = autofs4_wait(sbi, dentry, NFY_MOUNT);
@@ -280,20 +288,22 @@ static int autofs4_mount_wait(struct dentry *dentry)
return status;
}
-static int do_expire_wait(struct dentry *dentry)
+static int do_expire_wait(struct dentry *dentry, bool rcu_walk)
{
struct dentry *expiring;
- expiring = autofs4_lookup_expiring(dentry);
+ expiring = autofs4_lookup_expiring(dentry, rcu_walk);
+ if (IS_ERR(expiring))
+ return PTR_ERR(expiring);
if (!expiring)
- return autofs4_expire_wait(dentry);
+ return autofs4_expire_wait(dentry, rcu_walk);
else {
/*
* If we are racing with expire the request might not
* be quite complete, but the directory has been removed
* so it must have been successful, just wait for it.
*/
- autofs4_expire_wait(expiring);
+ autofs4_expire_wait(expiring, 0);
autofs4_del_expiring(expiring);
dput(expiring);
}
@@ -345,7 +355,7 @@ static struct vfsmount *autofs4_d_automount(struct path *path)
* and the directory was removed, so just go ahead and try
* the mount.
*/
- status = do_expire_wait(dentry);
+ status = do_expire_wait(dentry, 0);
if (status && status != -EAGAIN)
return NULL;
@@ -353,7 +363,7 @@ static struct vfsmount *autofs4_d_automount(struct path *path)
spin_lock(&sbi->fs_lock);
if (ino->flags & AUTOFS_INF_PENDING) {
spin_unlock(&sbi->fs_lock);
- status = autofs4_mount_wait(dentry);
+ status = autofs4_mount_wait(dentry, 0);
if (status)
return ERR_PTR(status);
goto done;
@@ -394,7 +404,7 @@ static struct vfsmount *autofs4_d_automount(struct path *path)
}
ino->flags |= AUTOFS_INF_PENDING;
spin_unlock(&sbi->fs_lock);
- status = autofs4_mount_wait(dentry);
+ status = autofs4_mount_wait(dentry, 0);
spin_lock(&sbi->fs_lock);
ino->flags &= ~AUTOFS_INF_PENDING;
if (status) {
@@ -423,28 +433,46 @@ 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;
}
- /* We need to sleep, so we need pathwalk to be in ref-mode */
- if (rcu_walk)
- return -ECHILD;
-
/* Wait for pending expires */
- do_expire_wait(dentry);
+ if (do_expire_wait(dentry, rcu_walk) == -ECHILD)
+ return -ECHILD;
/*
* This dentry may be under construction so wait on mount
* completion.
*/
- status = autofs4_mount_wait(dentry);
+ status = autofs4_mount_wait(dentry, rcu_walk);
if (status)
return status;
+ 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);
/*
* If the dentry has been selected for expire while we slept
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-29 08:07:57 +0100