From f55fb0c24386cee8b78f60d60186716bd0909493 Mon Sep 17 00:00:00 2001 From: Ian Kent Date: Fri, 14 Dec 2012 10:23:23 +0800 Subject: [PATCH 1/2] autofs4 - dont clear DCACHE_NEED_AUTOMOUNT on rootless mount 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 Signed-off-by: Linus Torvalds --- fs/autofs4/expire.c | 9 ------- fs/autofs4/root.c | 61 ++++++++++++++++++++++++++------------------- 2 files changed, 36 insertions(+), 34 deletions(-) diff --git a/fs/autofs4/expire.c b/fs/autofs4/expire.c index 842d00048a6..01443ce43ee 100644 --- a/fs/autofs4/expire.c +++ b/fs/autofs4/expire.c @@ -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); diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c index 91b11650722..30a6ab66e99 100644 --- a/fs/autofs4/root.c +++ b/fs/autofs4/root.c @@ -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 */ From 0259cb02c4004d3088b0999799f8f5c8801f6b97 Mon Sep 17 00:00:00 2001 From: Ian Kent Date: Fri, 14 Dec 2012 10:23:29 +0800 Subject: [PATCH 2/2] autofs4 - use simple_empty() for empty directory check For direct (and offset) mounts, if an automounted mount is manually umounted the trigger mount dentry can appear non-empty causing it to not trigger mounts. This can also happen if there is a file handle leak in a user space automounting application. This happens because, when a ioctl control file handle is opened on the mount, a cursor dentry is created which causes list_empty() to see the dentry as non-empty. Since there is a case where listing the directory of these dentrys is needed, the use of dcache_dir_*() functions for .open() and .release() is needed. Consequently simple_empty() must be used instead of list_empty() when checking for an empty directory. Signed-off-by: Ian Kent Signed-off-by: Linus Torvalds --- fs/autofs4/root.c | 22 +++++----------------- 1 file changed, 5 insertions(+), 17 deletions(-) diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c index 30a6ab66e99..c93447604da 100644 --- a/fs/autofs4/root.c +++ b/fs/autofs4/root.c @@ -124,13 +124,10 @@ static int autofs4_dir_open(struct inode *inode, struct file *file) * it. */ spin_lock(&sbi->lookup_lock); - spin_lock(&dentry->d_lock); - if (!d_mountpoint(dentry) && list_empty(&dentry->d_subdirs)) { - spin_unlock(&dentry->d_lock); + if (!d_mountpoint(dentry) && simple_empty(dentry)) { spin_unlock(&sbi->lookup_lock); return -ENOENT; } - spin_unlock(&dentry->d_lock); spin_unlock(&sbi->lookup_lock); out: @@ -386,12 +383,8 @@ static struct vfsmount *autofs4_d_automount(struct path *path) goto done; } } else { - spin_lock(&dentry->d_lock); - if (!list_empty(&dentry->d_subdirs)) { - spin_unlock(&dentry->d_lock); + if (!simple_empty(dentry)) goto done; - } - spin_unlock(&dentry->d_lock); } ino->flags |= AUTOFS_INF_PENDING; spin_unlock(&sbi->fs_lock); @@ -610,9 +603,7 @@ static int autofs4_dir_unlink(struct inode *dir, struct dentry *dentry) spin_lock(&sbi->lookup_lock); __autofs4_add_expiring(dentry); - spin_lock(&dentry->d_lock); - __d_drop(dentry); - spin_unlock(&dentry->d_lock); + d_drop(dentry); spin_unlock(&sbi->lookup_lock); return 0; @@ -683,15 +674,12 @@ static int autofs4_dir_rmdir(struct inode *dir, struct dentry *dentry) return -EACCES; spin_lock(&sbi->lookup_lock); - spin_lock(&dentry->d_lock); - if (!list_empty(&dentry->d_subdirs)) { - spin_unlock(&dentry->d_lock); + if (!simple_empty(dentry)) { spin_unlock(&sbi->lookup_lock); return -ENOTEMPTY; } __autofs4_add_expiring(dentry); - __d_drop(dentry); - spin_unlock(&dentry->d_lock); + d_drop(dentry); spin_unlock(&sbi->lookup_lock); if (sbi->version < 5)