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autofs4: always use lookup for lookup

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We need to be able to cope with the directory mutex being held during
->d_revalidate() in some cases, but not all cases, and not necessarily by
us.  Because we need to release the mutex when we call back to the daemon
to do perform a mount we must be sure that it is us who holds the mutex so
we must redirect mount requests to ->lookup() if the mutex is held.

Signed-off-by: Ian Kent <raven@themaw.net>
Cc: Sage Weil <sage@newdream.net>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Andreas Dilger <adilger@sun.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Yehuda Saheh <yehuda@newdream.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Ian Kent 2009-12-15 16:45:51 -08:00 committed by Linus Torvalds
parent cb4b492ac7
commit 213614d583
4 changed files with 331 additions and 159 deletions
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7
fs/autofs4/autofs_i.h
View file

@ -60,6 +60,11 @@ do { \
current->pid, __func__, ##args); \
} while (0)
struct rehash_entry {
struct task_struct *task;
struct list_head list;
};
/* Unified info structure. This is pointed to by both the dentry and
inode structures. Each file in the filesystem has an instance of this
structure. It holds a reference to the dentry, so dentries are never
@ -76,6 +81,7 @@ struct autofs_info {
struct list_head active;
int active_count;
struct list_head rehash_list;
struct list_head expiring;
@ -98,6 +104,7 @@ struct autofs_info {
#define AUTOFS_INF_EXPIRING (1<<0) /* dentry is in the process of expiring */
#define AUTOFS_INF_MOUNTPOINT (1<<1) /* mountpoint status for direct expire */
#define AUTOFS_INF_PENDING (1<<2) /* dentry pending mount */
#define AUTOFS_INF_REHASH (1<<3) /* dentry in transit to ->lookup() */
struct autofs_wait_queue {
wait_queue_head_t queue;

6
fs/autofs4/expire.c
View file

@ -279,6 +279,7 @@ struct dentry *autofs4_expire_direct(struct super_block *sb,
root->d_mounted--;
}
ino->flags |= AUTOFS_INF_EXPIRING;
autofs4_add_expiring(root);
init_completion(&ino->expire_complete);
spin_unlock(&sbi->fs_lock);
return root;
@ -406,6 +407,7 @@ found:
expired, (int)expired->d_name.len, expired->d_name.name);
ino = autofs4_dentry_ino(expired);
ino->flags |= AUTOFS_INF_EXPIRING;
autofs4_add_expiring(expired);
init_completion(&ino->expire_complete);
spin_unlock(&sbi->fs_lock);
spin_lock(&dcache_lock);
@ -433,7 +435,7 @@ int autofs4_expire_wait(struct dentry *dentry)
DPRINTK("expire done status=%d", status);
if (d_unhashed(dentry))
if (d_unhashed(dentry) && IS_DEADDIR(dentry->d_inode))
return -EAGAIN;
return status;
@ -473,6 +475,7 @@ int autofs4_expire_run(struct super_block *sb,
spin_lock(&sbi->fs_lock);
ino = autofs4_dentry_ino(dentry);
ino->flags &= ~AUTOFS_INF_EXPIRING;
autofs4_del_expiring(dentry);
complete_all(&ino->expire_complete);
spin_unlock(&sbi->fs_lock);
@ -503,6 +506,7 @@ int autofs4_do_expire_multi(struct super_block *sb, struct vfsmount *mnt,
ino->flags &= ~AUTOFS_INF_MOUNTPOINT;
}
ino->flags &= ~AUTOFS_INF_EXPIRING;
autofs4_del_expiring(dentry);
complete_all(&ino->expire_complete);
spin_unlock(&sbi->fs_lock);
dput(dentry);

1
fs/autofs4/inode.c
View file

@ -49,6 +49,7 @@ struct autofs_info *autofs4_init_ino(struct autofs_info *ino,
ino->dentry = NULL;
ino->size = 0;
INIT_LIST_HEAD(&ino->active);
INIT_LIST_HEAD(&ino->rehash_list);
ino->active_count = 0;
INIT_LIST_HEAD(&ino->expiring);
atomic_set(&ino->count, 0);

424
fs/autofs4/root.c
View file

@ -104,6 +104,99 @@ static void autofs4_del_active(struct dentry *dentry)
return;
}
static void autofs4_add_rehash_entry(struct autofs_info *ino,
struct rehash_entry *entry)
{
entry->task = current;
INIT_LIST_HEAD(&entry->list);
list_add(&entry->list, &ino->rehash_list);
return;
}
static void autofs4_remove_rehash_entry(struct autofs_info *ino)
{
struct list_head *head = &ino->rehash_list;
struct rehash_entry *entry;
list_for_each_entry(entry, head, list) {
if (entry->task == current) {
list_del(&entry->list);
kfree(entry);
break;
}
}
return;
}
static void autofs4_remove_rehash_entrys(struct autofs_info *ino)
{
struct autofs_sb_info *sbi = ino->sbi;
struct rehash_entry *entry, *next;
struct list_head *head;
spin_lock(&sbi->fs_lock);
spin_lock(&sbi->lookup_lock);
if (!(ino->flags & AUTOFS_INF_REHASH)) {
spin_unlock(&sbi->lookup_lock);
spin_unlock(&sbi->fs_lock);
return;
}
ino->flags &= ~AUTOFS_INF_REHASH;
head = &ino->rehash_list;
list_for_each_entry_safe(entry, next, head, list) {
list_del(&entry->list);
kfree(entry);
}
spin_unlock(&sbi->lookup_lock);
spin_unlock(&sbi->fs_lock);
dput(ino->dentry);
return;
}
static void autofs4_revalidate_drop(struct dentry *dentry,
struct rehash_entry *entry)
{
struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
struct autofs_info *ino = autofs4_dentry_ino(dentry);
/*
* Add to the active list so we can pick this up in
* ->lookup(). Also add an entry to a rehash list so
* we know when there are no dentrys in flight so we
* know when we can rehash the dentry.
*/
spin_lock(&sbi->lookup_lock);
if (list_empty(&ino->active))
list_add(&ino->active, &sbi->active_list);
autofs4_add_rehash_entry(ino, entry);
spin_unlock(&sbi->lookup_lock);
if (!(ino->flags & AUTOFS_INF_REHASH)) {
ino->flags |= AUTOFS_INF_REHASH;
dget(dentry);
spin_lock(&dentry->d_lock);
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
}
return;
}
static void autofs4_revalidate_rehash(struct dentry *dentry)
{
struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
struct autofs_info *ino = autofs4_dentry_ino(dentry);
if (ino->flags & AUTOFS_INF_REHASH) {
spin_lock(&sbi->lookup_lock);
autofs4_remove_rehash_entry(ino);
if (list_empty(&ino->rehash_list)) {
spin_unlock(&sbi->lookup_lock);
ino->flags &= ~AUTOFS_INF_REHASH;
d_rehash(dentry);
dput(ino->dentry);
} else
spin_unlock(&sbi->lookup_lock);
}
return;
}
static unsigned int autofs4_need_mount(unsigned int flags)
{
unsigned int res = 0;
@ -143,7 +236,7 @@ out:
return dcache_dir_open(inode, file);
}
static int try_to_fill_dentry(struct dentry *dentry, int flags)
static int try_to_fill_dentry(struct dentry *dentry)
{
struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
struct autofs_info *ino = autofs4_dentry_ino(dentry);
@ -156,7 +249,6 @@ static int try_to_fill_dentry(struct dentry *dentry, int flags)
* Wait for a pending mount, triggering one if there
* isn't one already
*/
if (dentry->d_inode == NULL) {
DPRINTK("waiting for mount name=%.*s",
dentry->d_name.len, dentry->d_name.name);
@ -164,47 +256,10 @@ static int try_to_fill_dentry(struct dentry *dentry, int flags)
DPRINTK("mount done status=%d", status);
/* Turn this into a real negative dentry? */
if (status == -ENOENT) {
spin_lock(&sbi->fs_lock);
ino->flags &= ~AUTOFS_INF_PENDING;
spin_unlock(&sbi->fs_lock);
return status;
} else if (status) {
/* Return a negative dentry, but leave it "pending" */
return status;
}
/* Trigger mount for path component or follow link */
} else if (ino->flags & AUTOFS_INF_PENDING ||
autofs4_need_mount(flags) ||
current->link_count) {
DPRINTK("waiting for mount name=%.*s",
dentry->d_name.len, dentry->d_name.name);
spin_lock(&sbi->fs_lock);
ino->flags |= AUTOFS_INF_PENDING;
spin_unlock(&sbi->fs_lock);
status = autofs4_wait(sbi, dentry, NFY_MOUNT);
DPRINTK("mount done status=%d", status);
if (status) {
spin_lock(&sbi->fs_lock);
ino->flags &= ~AUTOFS_INF_PENDING;
spin_unlock(&sbi->fs_lock);
return status;
}
}
/* Initialize expiry counter after successful mount */
if (ino)
/* Update expiry counter */
ino->last_used = jiffies;
spin_lock(&sbi->fs_lock);
ino->flags &= ~AUTOFS_INF_PENDING;
spin_unlock(&sbi->fs_lock);
return 0;
return status;
}
/* For autofs direct mounts the follow link triggers the mount */
@ -258,10 +313,16 @@ static void *autofs4_follow_link(struct dentry *dentry, struct nameidata *nd)
*/
if (ino->flags & AUTOFS_INF_PENDING ||
(!d_mountpoint(dentry) && list_empty(&dentry->d_subdirs))) {
ino->flags |= AUTOFS_INF_PENDING;
spin_unlock(&dcache_lock);
spin_unlock(&sbi->fs_lock);
status = try_to_fill_dentry(dentry, 0);
status = try_to_fill_dentry(dentry);
spin_lock(&sbi->fs_lock);
ino->flags &= ~AUTOFS_INF_PENDING;
spin_unlock(&sbi->fs_lock);
if (status)
goto out_error;
@ -300,19 +361,48 @@ static int autofs4_revalidate(struct dentry *dentry, struct nameidata *nd)
{
struct inode *dir = dentry->d_parent->d_inode;
struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb);
int oz_mode = autofs4_oz_mode(sbi);
struct autofs_info *ino = autofs4_dentry_ino(dentry);
struct rehash_entry *entry;
int flags = nd ? nd->flags : 0;
int status = 1;
unsigned int mutex_aquired;
/* Pending dentry */
spin_lock(&sbi->fs_lock);
if (autofs4_ispending(dentry)) {
/* The daemon never causes a mount to trigger */
spin_unlock(&sbi->fs_lock);
DPRINTK("name = %.*s oz_mode = %d",
dentry->d_name.len, dentry->d_name.name, oz_mode);
if (oz_mode)
/* Daemon never causes a mount to trigger */
if (autofs4_oz_mode(sbi))
return 1;
entry = kmalloc(sizeof(struct rehash_entry), GFP_KERNEL);
if (!entry)
return -ENOMEM;
mutex_aquired = mutex_trylock(&dir->i_mutex);
spin_lock(&sbi->fs_lock);
spin_lock(&dcache_lock);
/* Pending dentry */
if (autofs4_ispending(dentry)) {
int status;
/*
* We can only unhash and send this to ->lookup() if
* the directory mutex is held over d_revalidate() and
* ->lookup(). This prevents the VFS from incorrectly
* seeing the dentry as non-existent.
*/
ino->flags |= AUTOFS_INF_PENDING;
if (!mutex_aquired) {
autofs4_revalidate_drop(dentry, entry);
spin_unlock(&dcache_lock);
spin_unlock(&sbi->fs_lock);
return 0;
}
spin_unlock(&dcache_lock);
spin_unlock(&sbi->fs_lock);
mutex_unlock(&dir->i_mutex);
kfree(entry);
/*
* If the directory has gone away due to an expire
* we have been called as ->d_revalidate() and so
@ -325,45 +415,82 @@ static int autofs4_revalidate(struct dentry *dentry, struct nameidata *nd)
* A zero status is success otherwise we have a
* negative error code.
*/
status = try_to_fill_dentry(dentry, flags);
status = try_to_fill_dentry(dentry);
spin_lock(&sbi->fs_lock);
ino->flags &= ~AUTOFS_INF_PENDING;
spin_unlock(&sbi->fs_lock);
if (status == 0)
return 1;
return status;
}
spin_unlock(&sbi->fs_lock);
/* Negative dentry.. invalidate if "old" */
if (dentry->d_inode == NULL)
return 0;
/* Check for a non-mountpoint directory with no contents */
spin_lock(&dcache_lock);
if (S_ISDIR(dentry->d_inode->i_mode) &&
!d_mountpoint(dentry) && list_empty(&dentry->d_subdirs)) {
DPRINTK("dentry=%p %.*s, emptydir",
dentry, dentry->d_name.len, dentry->d_name.name);
spin_unlock(&dcache_lock);
/* The daemon never causes a mount to trigger */
if (oz_mode)
return 1;
if (autofs4_need_mount(flags) || current->link_count) {
int status;
/*
* We can only unhash and send this to ->lookup() if
* the directory mutex is held over d_revalidate() and
* ->lookup(). This prevents the VFS from incorrectly
* seeing the dentry as non-existent.
*/
ino->flags |= AUTOFS_INF_PENDING;
if (!mutex_aquired) {
autofs4_revalidate_drop(dentry, entry);
spin_unlock(&dcache_lock);
spin_unlock(&sbi->fs_lock);
return 0;
}
spin_unlock(&dcache_lock);
spin_unlock(&sbi->fs_lock);
mutex_unlock(&dir->i_mutex);
kfree(entry);
/*
* A zero status is success otherwise we have a
* negative error code.
*/
status = try_to_fill_dentry(dentry, flags);
status = try_to_fill_dentry(dentry);
spin_lock(&sbi->fs_lock);
ino->flags &= ~AUTOFS_INF_PENDING;
spin_unlock(&sbi->fs_lock);
if (status == 0)
return 1;
return status;
}
}
spin_unlock(&dcache_lock);
spin_unlock(&sbi->fs_lock);
if (mutex_aquired)
mutex_unlock(&dir->i_mutex);
kfree(entry);
return 1;
}
static void autofs4_free_rehash_entrys(struct autofs_info *inf)
{
struct list_head *head = &inf->rehash_list;
struct rehash_entry *entry, *next;
list_for_each_entry_safe(entry, next, head, list) {
list_del(&entry->list);
kfree(entry);
}
}
void autofs4_dentry_release(struct dentry *de)
{
struct autofs_info *inf;
@ -382,6 +509,8 @@ void autofs4_dentry_release(struct dentry *de)
list_del(&inf->active);
if (!list_empty(&inf->expiring))
list_del(&inf->expiring);
if (!list_empty(&inf->rehash_list))
autofs4_free_rehash_entrys(inf);
spin_unlock(&sbi->lookup_lock);
}
@ -414,6 +543,7 @@ static struct dentry *autofs4_lookup_active(struct dentry *dentry)
const unsigned char *str = name->name;
struct list_head *p, *head;
restart:
spin_lock(&dcache_lock);
spin_lock(&sbi->lookup_lock);
head = &sbi->active_list;
@ -431,6 +561,19 @@ static struct dentry *autofs4_lookup_active(struct dentry *dentry)
if (atomic_read(&active->d_count) == 0)
goto next;
if (active->d_inode && IS_DEADDIR(active->d_inode)) {
if (!list_empty(&ino->rehash_list)) {
dget(active);
spin_unlock(&active->d_lock);
spin_unlock(&sbi->lookup_lock);
spin_unlock(&dcache_lock);
autofs4_remove_rehash_entrys(ino);
dput(active);
goto restart;
}
goto next;
}
qstr = &active->d_name;
if (active->d_name.hash != hash)
@ -443,13 +586,11 @@ static struct dentry *autofs4_lookup_active(struct dentry *dentry)
if (memcmp(qstr->name, str, len))
goto next;
if (d_unhashed(active)) {
dget(active);
spin_unlock(&active->d_lock);
spin_unlock(&sbi->lookup_lock);
spin_unlock(&dcache_lock);
return active;
}
next:
spin_unlock(&active->d_lock);
}
@ -498,13 +639,11 @@ static struct dentry *autofs4_lookup_expiring(struct dentry *dentry)
if (memcmp(qstr->name, str, len))
goto next;
if (d_unhashed(expiring)) {
dget(expiring);
spin_unlock(&expiring->d_lock);
spin_unlock(&sbi->lookup_lock);
spin_unlock(&dcache_lock);
return expiring;
}
next:
spin_unlock(&expiring->d_lock);
}
@ -514,32 +653,11 @@ next:
return NULL;
}
/* Lookups in the root directory */
static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
static struct autofs_info *init_new_dentry(struct autofs_sb_info *sbi,
struct dentry *dentry, int oz_mode)
{
struct autofs_sb_info *sbi;
struct autofs_info *ino;
struct dentry *expiring, *active;
int oz_mode;
DPRINTK("name = %.*s",
dentry->d_name.len, dentry->d_name.name);
/* File name too long to exist */
if (dentry->d_name.len > NAME_MAX)
return ERR_PTR(-ENAMETOOLONG);
sbi = autofs4_sbi(dir->i_sb);
oz_mode = autofs4_oz_mode(sbi);
DPRINTK("pid = %u, pgrp = %u, catatonic = %d, oz_mode = %d",
current->pid, task_pgrp_nr(current), sbi->catatonic, oz_mode);
active = autofs4_lookup_active(dentry);
if (active) {
dentry = active;
ino = autofs4_dentry_ino(dentry);
} else {
/*
* Mark the dentry incomplete but don't hash it. We do this
* to serialize our inode creation operations (symlink and
@ -565,14 +683,60 @@ static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, s
dentry->d_fsdata = ino;
ino->dentry = dentry;
autofs4_add_active(dentry);
/*
* Only set the mount pending flag for new dentrys not created
* by the daemon.
*/
if (!oz_mode)
ino->flags |= AUTOFS_INF_PENDING;
d_instantiate(dentry, NULL);
return ino;
}
/* Lookups in the root directory */
static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
{
struct autofs_sb_info *sbi;
struct autofs_info *ino;
struct dentry *expiring, *active;
int oz_mode;
int status = 0;
DPRINTK("name = %.*s",
dentry->d_name.len, dentry->d_name.name);
/* File name too long to exist */
if (dentry->d_name.len > NAME_MAX)
return ERR_PTR(-ENAMETOOLONG);
sbi = autofs4_sbi(dir->i_sb);
oz_mode = autofs4_oz_mode(sbi);
DPRINTK("pid = %u, pgrp = %u, catatonic = %d, oz_mode = %d",
current->pid, task_pgrp_nr(current), sbi->catatonic, oz_mode);
spin_lock(&sbi->fs_lock);
active = autofs4_lookup_active(dentry);
if (active) {
dentry = active;
ino = autofs4_dentry_ino(dentry);
/* If this came from revalidate, rehash it */
autofs4_revalidate_rehash(dentry);
spin_unlock(&sbi->fs_lock);
} else {
spin_unlock(&sbi->fs_lock);
ino = init_new_dentry(sbi, dentry, oz_mode);
if (IS_ERR(ino))
return (struct dentry *) ino;
}
autofs4_add_active(dentry);
if (!oz_mode) {
mutex_unlock(&dir->i_mutex);
expiring = autofs4_lookup_expiring(dentry);
mutex_unlock(&dir->i_mutex);
if (expiring) {
/*
* If we are racing with expire the request might not
@ -580,23 +744,22 @@ static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, s
* so it must have been successful, so just wait for it.
*/
autofs4_expire_wait(expiring);
autofs4_del_expiring(expiring);
dput(expiring);
}
spin_lock(&sbi->fs_lock);
ino->flags |= AUTOFS_INF_PENDING;
spin_unlock(&sbi->fs_lock);
if (dentry->d_op && dentry->d_op->d_revalidate)
(dentry->d_op->d_revalidate)(dentry, nd);
status = try_to_fill_dentry(dentry);
mutex_lock(&dir->i_mutex);
spin_lock(&sbi->fs_lock);
ino->flags &= ~AUTOFS_INF_PENDING;
spin_unlock(&sbi->fs_lock);
}
autofs4_del_active(dentry);
/*
* If we are still pending, check if we had to handle
* If we had a mount fail, check if we had to handle
* a signal. If so we can force a restart..
*/
if (ino->flags & AUTOFS_INF_PENDING) {
if (status) {
/* See if we were interrupted */
if (signal_pending(current)) {
sigset_t *sigset = &current->pending.signal;
@ -608,42 +771,45 @@ static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, s
return ERR_PTR(-ERESTARTNOINTR);
}
}
if (!oz_mode) {
spin_lock(&sbi->fs_lock);
ino->flags &= ~AUTOFS_INF_PENDING;
spin_unlock(&sbi->fs_lock);
}
}
/*
* If this dentry is unhashed, then we shouldn't honour this
* lookup. Returning ENOENT here doesn't do the right thing
* for all system calls, but it should be OK for the operations
* we permit from an autofs.
* User space can (and has done in the past) remove and re-create
* this directory during the callback. This can leave us with an
* unhashed dentry, but a successful mount! So we need to
* perform another cached lookup in case the dentry now exists.
*/
if (!oz_mode && d_unhashed(dentry)) {
/*
* A user space application can (and has done in the past)
* remove and re-create this directory during the callback.
* This can leave us with an unhashed dentry, but a
* successful mount! So we need to perform another
* cached lookup in case the dentry now exists.
*/
struct dentry *parent = dentry->d_parent;
struct dentry *new = d_lookup(parent, &dentry->d_name);
if (new != NULL)
dentry = new;
else
dentry = ERR_PTR(-ENOENT);
if (!oz_mode && !have_submounts(dentry)) {
struct dentry *new;
new = d_lookup(dentry->d_parent, &dentry->d_name);
if (new) {
if (active)
dput(active);
return dentry;
return new;
} else {
if (!status)
status = -ENOENT;
}
}
/*
* If we had a mount failure, return status to user space.
* If the mount succeeded and we used a dentry from the active queue
* return it.
*/
if (status) {
dentry = ERR_PTR(status);
if (active)
dput(active);
return dentry;
} else {
/*
* Valid successful mount, return active dentry or NULL
* for a new dentry.
*/
if (active)
return active;
}
return NULL;
}
@ -668,8 +834,6 @@ static int autofs4_dir_symlink(struct inode *dir,
if (!ino)
return -ENOMEM;
autofs4_del_active(dentry);
ino->size = strlen(symname);
cp = kmalloc(ino->size + 1, GFP_KERNEL);
if (!cp) {
@ -746,7 +910,6 @@ static int autofs4_dir_unlink(struct inode *dir, struct dentry *dentry)
dir->i_mtime = CURRENT_TIME;
spin_lock(&dcache_lock);
autofs4_add_expiring(dentry);
spin_lock(&dentry->d_lock);
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
@ -772,7 +935,6 @@ static int autofs4_dir_rmdir(struct inode *dir, struct dentry *dentry)
spin_unlock(&dcache_lock);
return -ENOTEMPTY;
}
autofs4_add_expiring(dentry);
spin_lock(&dentry->d_lock);
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
@ -810,8 +972,6 @@ static int autofs4_dir_mkdir(struct inode *dir, struct dentry *dentry, int mode)
if (!ino)
return -ENOMEM;
autofs4_del_active(dentry);
inode = autofs4_get_inode(dir->i_sb, ino);
if (!inode) {
if (!dentry->d_fsdata)