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autofs4 - dont clear DCACHE_NEED_AUTOMOUNT on rootless mount

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The DCACHE_NEED_AUTOMOUNT flag is cleared on mount and set on expire
for autofs rootless multi-mount dentrys to prevent unnecessary calls
to ->d_automount().

Since DCACHE_MANAGE_TRANSIT is always set on autofs dentrys ->d_managed()
is always called so the check can be done in ->d_manage() without the
need to change the flag. This still avoids unnecessary calls to
->d_automount(), adds negligible overhead and eliminates a seriously
ugly check in the expire code.

Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Ian Kent 2012-12-14 10:23:23 +08:00 committed by Linus Torvalds
parent 29594404d7
commit f55fb0c243
2 changed files with 36 additions and 34 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

9
fs/autofs4/expire.c
View file

@ -548,15 +548,6 @@ 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) {
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);

61
fs/autofs4/root.c
View file

@ -355,7 +355,6 @@ static struct vfsmount *autofs4_d_automount(struct path *path)
status = autofs4_mount_wait(dentry);
if (status)
return ERR_PTR(status);
spin_lock(&sbi->fs_lock);
goto done;
}
@ -364,8 +363,11 @@ static struct vfsmount *autofs4_d_automount(struct path *path)
* 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))
if (dentry->d_inode && S_ISLNK(dentry->d_inode->i_mode)) {
spin_unlock(&sbi->fs_lock);
goto done;
}
if (!d_mountpoint(dentry)) {
/*
* It's possible that user space hasn't removed directories
@ -379,8 +381,10 @@ static struct vfsmount *autofs4_d_automount(struct path *path)
* require user space behave.
*/
if (sbi->version > 4) {
if (have_submounts(dentry))
if (have_submounts(dentry)) {
spin_unlock(&sbi->fs_lock);
goto done;
}
} else {
spin_lock(&dentry->d_lock);
if (!list_empty(&dentry->d_subdirs)) {
@ -399,28 +403,8 @@ static struct vfsmount *autofs4_d_automount(struct path *path)
return ERR_PTR(status);
}
}
done:
if (!(ino->flags & AUTOFS_INF_EXPIRING)) {
/*
* 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.
*
* 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.
*/
spin_lock(&dentry->d_lock);
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);
done:
/* Mount succeeded, check if we ended up with a new dentry */
dentry = autofs4_mountpoint_changed(path);
if (!dentry)
@ -432,6 +416,8 @@ done:
int autofs4_d_manage(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;
DPRINTK("dentry=%p %.*s",
dentry, dentry->d_name.len, dentry->d_name.name);
@ -456,7 +442,32 @@ int autofs4_d_manage(struct dentry *dentry, bool rcu_walk)
* This dentry may be under construction so wait on mount
* completion.
*/
return autofs4_mount_wait(dentry);
status = autofs4_mount_wait(dentry);
if (status)
return status;
spin_lock(&sbi->fs_lock);
/*
* If the dentry has been selected for expire while we slept
* on the lock then it might go away. We'll deal with that in
* ->d_automount() and wait on a new mount if the expire
* succeeds or return here if it doesn't (since there's no
* mount to follow with a rootless multi-mount).
*/
if (!(ino->flags & AUTOFS_INF_EXPIRING)) {
/*
* Any needed mounting has been completed and the path
* updated so check if this is a rootless multi-mount so
* we can avoid needless calls ->d_automount() and avoid
* an incorrect ELOOP error return.
*/
if ((!d_mountpoint(dentry) && !simple_empty(dentry)) ||
(dentry->d_inode && S_ISLNK(dentry->d_inode->i_mode)))
status = -EISDIR;
}
spin_unlock(&sbi->fs_lock);
return status;
}
/* Lookups in the root directory */