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autofs4: Add d_manage() dentry operation

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This patch required a previous patch to add the ->d_automount()
dentry operation.

Add a function to use the newly defined ->d_manage() dentry operation
for blocking during mount and expire.

Whether the VFS calls the dentry operations d_automount() and d_manage()
is controled by the DMANAGED_AUTOMOUNT and DMANAGED_TRANSIT flags. autofs
uses the d_automount() operation to callback to user space to request
mount operations and the d_manage() operation to block walks into mounts
that are under construction or destruction.

In order to prevent these functions from being called unnecessarily the
DMANAGED_* flags are cleared for cases which would cause this. In the
common case the DMANAGED_AUTOMOUNT and DMANAGED_TRANSIT flags are both
set for dentrys waiting to be mounted. The DMANAGED_TRANSIT flag is
cleared upon successful mount request completion and set during expire
runs, both during the dentry expire check, and if selected for expire,
is left set until a subsequent successful mount request completes.

The exception to this is the so-called rootless multi-mount which has
no actual mount at its base. In this case the DMANAGED_AUTOMOUNT flag
is cleared upon successful mount request completion as well and set
again after a successful expire.

Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Ian Kent 2011-01-14 18:46:03 +00:00 committed by Al Viro
parent 10584211e4
commit b5b801779d
4 changed files with 159 additions and 40 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

50
fs/autofs4/autofs_i.h
View File

@ -99,7 +99,6 @@ 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 */
struct autofs_wait_queue {
@ -221,6 +220,7 @@ extern const struct file_operations autofs4_root_operations;
/* Operations methods */
struct vfsmount *autofs4_d_automount(struct path *);
int autofs4_d_manage(struct dentry *, bool);
/* VFS automount flags management functions */
@ -248,6 +248,54 @@ static inline void managed_dentry_clear_automount(struct dentry *dentry)
spin_unlock(&dentry->d_lock);
}
static inline void __managed_dentry_set_transit(struct dentry *dentry)
{
dentry->d_flags |= DCACHE_MANAGE_TRANSIT;
}
static inline void managed_dentry_set_transit(struct dentry *dentry)
{
spin_lock(&dentry->d_lock);
__managed_dentry_set_transit(dentry);
spin_unlock(&dentry->d_lock);
}
static inline void __managed_dentry_clear_transit(struct dentry *dentry)
{
dentry->d_flags &= ~DCACHE_MANAGE_TRANSIT;
}
static inline void managed_dentry_clear_transit(struct dentry *dentry)
{
spin_lock(&dentry->d_lock);
__managed_dentry_clear_transit(dentry);
spin_unlock(&dentry->d_lock);
}
static inline void __managed_dentry_set_managed(struct dentry *dentry)
{
dentry->d_flags |= (DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT);
}
static inline void managed_dentry_set_managed(struct dentry *dentry)
{
spin_lock(&dentry->d_lock);
__managed_dentry_set_managed(dentry);
spin_unlock(&dentry->d_lock);
}
static inline void __managed_dentry_clear_managed(struct dentry *dentry)
{
dentry->d_flags &= ~(DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT);
}
static inline void managed_dentry_clear_managed(struct dentry *dentry)
{
spin_lock(&dentry->d_lock);
__managed_dentry_clear_managed(dentry);
spin_unlock(&dentry->d_lock);
}
/* Initializing function */
int autofs4_fill_super(struct super_block *, void *, int);

51
fs/autofs4/expire.c
View File

@ -26,10 +26,6 @@ static inline int autofs4_can_expire(struct dentry *dentry,
if (ino == NULL)
return 0;
/* No point expiring a pending mount */
if (ino->flags & AUTOFS_INF_PENDING)
return 0;
if (!do_now) {
/* Too young to die */
if (!timeout || time_after(ino->last_used + timeout, now))
@ -283,6 +279,7 @@ struct dentry *autofs4_expire_direct(struct super_block *sb,
unsigned long timeout;
struct dentry *root = dget(sb->s_root);
int do_now = how & AUTOFS_EXP_IMMEDIATE;
struct autofs_info *ino;
if (!root)
return NULL;
@ -291,20 +288,21 @@ struct dentry *autofs4_expire_direct(struct super_block *sb,
timeout = sbi->exp_timeout;
spin_lock(&sbi->fs_lock);
ino = autofs4_dentry_ino(root);
/* No point expiring a pending mount */
if (ino->flags & AUTOFS_INF_PENDING) {
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);
if (d_mountpoint(root)) {
ino->flags |= AUTOFS_INF_MOUNTPOINT;
spin_lock(&root->d_lock);
root->d_flags &= ~DCACHE_MOUNTED;
spin_unlock(&root->d_lock);
}
ino->flags |= AUTOFS_INF_EXPIRING;
managed_dentry_set_automount(root);
init_completion(&ino->expire_complete);
spin_unlock(&sbi->fs_lock);
return root;
}
managed_dentry_clear_transit(root);
spin_unlock(&sbi->fs_lock);
dput(root);
@ -341,6 +339,10 @@ struct dentry *autofs4_expire_indirect(struct super_block *sb,
while ((dentry = get_next_positive_dentry(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 cont;
managed_dentry_set_transit(dentry);
/*
* Case 1: (i) indirect mount or top level pseudo direct mount
@ -400,6 +402,8 @@ struct dentry *autofs4_expire_indirect(struct super_block *sb,
}
}
next:
managed_dentry_clear_transit(dentry);
cont:
spin_unlock(&sbi->fs_lock);
}
return NULL;
@ -409,7 +413,6 @@ found:
expired, (int)expired->d_name.len, expired->d_name.name);
ino = autofs4_dentry_ino(expired);
ino->flags |= AUTOFS_INF_EXPIRING;
managed_dentry_set_automount(expired);
init_completion(&ino->expire_complete);
spin_unlock(&sbi->fs_lock);
spin_lock(&autofs4_lock);
@ -482,7 +485,7 @@ int autofs4_expire_run(struct super_block *sb,
ino = autofs4_dentry_ino(dentry);
ino->flags &= ~AUTOFS_INF_EXPIRING;
if (!d_unhashed(dentry))
managed_dentry_clear_automount(dentry);
managed_dentry_clear_transit(dentry);
complete_all(&ino->expire_complete);
spin_unlock(&sbi->fs_lock);
@ -508,20 +511,18 @@ int autofs4_do_expire_multi(struct super_block *sb, struct vfsmount *mnt,
ret = autofs4_wait(sbi, dentry, NFY_EXPIRE);
spin_lock(&sbi->fs_lock);
if (ino->flags & AUTOFS_INF_MOUNTPOINT) {
spin_lock(&sb->s_root->d_lock);
/*
* If we haven't been expired away, then reset
* mounted status.
*/
if (mnt->mnt_parent != mnt)
sb->s_root->d_flags |= DCACHE_MOUNTED;
spin_unlock(&sb->s_root->d_lock);
ino->flags &= ~AUTOFS_INF_MOUNTPOINT;
}
ino->flags &= ~AUTOFS_INF_EXPIRING;
spin_lock(&dentry->d_lock);
if (ret)
managed_dentry_clear_automount(dentry);
__managed_dentry_clear_transit(dentry);
else {
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);

3
fs/autofs4/inode.c
View File

@ -253,6 +253,7 @@ static struct autofs_info *autofs4_mkroot(struct autofs_sb_info *sbi)
static const struct dentry_operations autofs4_sb_dentry_operations = {
.d_automount = autofs4_d_automount,
.d_manage = autofs4_d_manage,
.d_release = autofs4_dentry_release,
};
@ -322,7 +323,7 @@ int autofs4_fill_super(struct super_block *s, void *data, int silent)
}
if (autofs_type_trigger(sbi->type))
__managed_dentry_set_automount(root);
__managed_dentry_set_managed(root);
root_inode->i_fop = &autofs4_root_operations;
root_inode->i_op = autofs_type_trigger(sbi->type) ?

95
fs/autofs4/root.c
View File

@ -424,6 +424,7 @@ static const struct dentry_operations autofs4_root_dentry_operations = {
/* For other dentries */
static const struct dentry_operations autofs4_dentry_operations = {
.d_automount = autofs4_d_automount,
.d_manage = autofs4_d_manage,
.d_release = autofs4_dentry_release,
};
@ -604,6 +605,18 @@ 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;
@ -633,31 +646,63 @@ struct vfsmount *autofs4_d_automount(struct path *path)
/*
* If the dentry is a symlink it's equivalent to a directory
* having d_mounted() true, so there's no need to call back
* 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))
goto done;
spin_lock(&dentry->d_lock);
if (!d_mountpoint(dentry) && list_empty(&dentry->d_subdirs)) {
if (!d_mountpoint(dentry)) {
/*
* It's possible that user space hasn't removed directories
* after umounting a rootless multi-mount, although it
* should. For v5 have_submounts() is sufficient to handle
* this because the leaves of the directory tree under the
* mount never trigger mounts themselves (they have an autofs
* trigger mount mounted on them). But v4 pseudo direct mounts
* do need the leaves to to trigger mounts. In this case we
* have no choice but to use the list_empty() check and
* require user space behave.
*/
if (sbi->version > 4) {
if (have_submounts(dentry))
goto done;
} else {
spin_lock(&dentry->d_lock);
if (!list_empty(&dentry->d_subdirs)) {
spin_unlock(&dentry->d_lock);
goto done;
}
spin_unlock(&dentry->d_lock);
}
ino->flags |= AUTOFS_INF_PENDING;
spin_unlock(&dentry->d_lock);
spin_unlock(&sbi->fs_lock);
status = autofs4_mount_wait(dentry);
if (status)
return ERR_PTR(status);
spin_lock(&sbi->fs_lock);
ino->flags &= ~AUTOFS_INF_PENDING;
goto done;
}
spin_unlock(&dentry->d_lock);
done:
/*
* 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().
*/
managed_dentry_clear_automount(dentry);
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().
*/
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
* an actual mount so ->d_automount() won't be called during
* the follow.
*/
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);
/* Mount succeeded, check if we ended up with a new dentry */
@ -668,6 +713,30 @@ done:
return NULL;
}
int autofs4_d_manage(struct dentry *dentry, bool mounting_here)
{
struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
DPRINTK("dentry=%p %.*s",
dentry, dentry->d_name.len, dentry->d_name.name);
/* The daemon never waits. */
if (autofs4_oz_mode(sbi) || mounting_here) {
if (!d_mountpoint(dentry))
return -EISDIR;
return 0;
}
/* Wait for pending expires */
do_expire_wait(dentry);
/*
* This dentry may be under construction so wait on mount
* completion.
*/
return autofs4_mount_wait(dentry);
}
/* Lookups in the root directory */
static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
{
@ -704,7 +773,7 @@ static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, s
/* Mark entries in the root as mount triggers */
if (autofs_type_indirect(sbi->type) && IS_ROOT(dentry->d_parent)) {
d_set_d_op(dentry, &autofs4_dentry_operations);
managed_dentry_set_automount(dentry);
__managed_dentry_set_managed(dentry);
}
ino = autofs4_init_ino(NULL, sbi, 0555);