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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
Download Patch File Download Diff File Expand all files Collapse all files

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);