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Merge branch 'work.autofs' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

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Pull autofs updates from Al Viro:
 "The most interesting part here is getting rid of the last trylock loop
  on dentry->d_lock.

  The ones in fs/dcache.c had been dealt with several years ago, but
  there'd been leftovers in fs/autofs/expire.c"

* 'work.autofs' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  autofs_lookup(): hold ->d_lock over playing with ->d_flags
  get rid of autofs_info->active_count
  autofs: simplify get_next_positive_...(), get rid of trylocks
This commit is contained in:
Linus Torvalds 2019-09-19 10:14:22 -07:00
commit 8e6ee05d8a
3 changed files with 44 additions and 104 deletions
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1
fs/autofs/autofs_i.h
View File

@ -58,7 +58,6 @@ struct autofs_info {
struct completion expire_complete;
struct list_head active;
int active_count;
struct list_head expiring;

103
fs/autofs/expire.c
View File

@ -70,6 +70,27 @@ static int autofs_mount_busy(struct vfsmount *mnt,
return status;
}
/* p->d_lock held */
static struct dentry *positive_after(struct dentry *p, struct dentry *child)
{
if (child)
child = list_next_entry(child, d_child);
else
child = list_first_entry(&p->d_subdirs, struct dentry, d_child);
list_for_each_entry_from(child, &p->d_subdirs, d_child) {
spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
if (simple_positive(child)) {
dget_dlock(child);
spin_unlock(&child->d_lock);
return child;
}
spin_unlock(&child->d_lock);
}
return NULL;
}
/*
* Calculate and dget next entry in the subdirs list under root.
*/
@ -77,43 +98,14 @@ static struct dentry *get_next_positive_subdir(struct dentry *prev,
struct dentry *root)
{
struct autofs_sb_info *sbi = autofs_sbi(root->d_sb);
struct list_head *next;
struct dentry *q;
spin_lock(&sbi->lookup_lock);
spin_lock(&root->d_lock);
if (prev)
next = prev->d_child.next;
else {
prev = dget_dlock(root);
next = prev->d_subdirs.next;
}
cont:
if (next == &root->d_subdirs) {
spin_unlock(&root->d_lock);
spin_unlock(&sbi->lookup_lock);
dput(prev);
return NULL;
}
q = list_entry(next, struct dentry, d_child);
spin_lock_nested(&q->d_lock, DENTRY_D_LOCK_NESTED);
/* Already gone or negative dentry (under construction) - try next */
if (!d_count(q) || !simple_positive(q)) {
spin_unlock(&q->d_lock);
next = q->d_child.next;
goto cont;
}
dget_dlock(q);
spin_unlock(&q->d_lock);
q = positive_after(root, prev);
spin_unlock(&root->d_lock);
spin_unlock(&sbi->lookup_lock);
dput(prev);
return q;
}
@ -124,59 +116,28 @@ static struct dentry *get_next_positive_dentry(struct dentry *prev,
struct dentry *root)
{
struct autofs_sb_info *sbi = autofs_sbi(root->d_sb);
struct list_head *next;
struct dentry *p, *ret;
struct dentry *p = prev, *ret = NULL, *d = NULL;
if (prev == NULL)
return dget(root);
spin_lock(&sbi->lookup_lock);
relock:
p = prev;
spin_lock(&p->d_lock);
again:
next = p->d_subdirs.next;
if (next == &p->d_subdirs) {
while (1) {
struct dentry *parent;
while (1) {
struct dentry *parent;
if (p == root) {
spin_unlock(&p->d_lock);
spin_unlock(&sbi->lookup_lock);
dput(prev);
return NULL;
}
parent = p->d_parent;
if (!spin_trylock(&parent->d_lock)) {
spin_unlock(&p->d_lock);
cpu_relax();
goto relock;
}
spin_unlock(&p->d_lock);
next = p->d_child.next;
p = parent;
if (next != &parent->d_subdirs)
break;
}
}
ret = list_entry(next, struct dentry, d_child);
spin_lock_nested(&ret->d_lock, DENTRY_D_LOCK_NESTED);
/* Negative dentry - try next */
if (!simple_positive(ret)) {
ret = positive_after(p, d);
if (ret || p == root)
break;
parent = p->d_parent;
spin_unlock(&p->d_lock);
lock_set_subclass(&ret->d_lock.dep_map, 0, _RET_IP_);
p = ret;
goto again;
spin_lock(&parent->d_lock);
d = p;
p = parent;
}
dget_dlock(ret);
spin_unlock(&ret->d_lock);
spin_unlock(&p->d_lock);
spin_unlock(&sbi->lookup_lock);
dput(prev);
return ret;
}

44
fs/autofs/root.c
View File

@ -60,38 +60,15 @@ const struct dentry_operations autofs_dentry_operations = {
.d_release = autofs_dentry_release,
};
static void autofs_add_active(struct dentry *dentry)
{
struct autofs_sb_info *sbi = autofs_sbi(dentry->d_sb);
struct autofs_info *ino;
ino = autofs_dentry_ino(dentry);
if (ino) {
spin_lock(&sbi->lookup_lock);
if (!ino->active_count) {
if (list_empty(&ino->active))
list_add(&ino->active, &sbi->active_list);
}
ino->active_count++;
spin_unlock(&sbi->lookup_lock);
}
}
static void autofs_del_active(struct dentry *dentry)
{
struct autofs_sb_info *sbi = autofs_sbi(dentry->d_sb);
struct autofs_info *ino;
ino = autofs_dentry_ino(dentry);
if (ino) {
spin_lock(&sbi->lookup_lock);
ino->active_count--;
if (!ino->active_count) {
if (!list_empty(&ino->active))
list_del_init(&ino->active);
}
spin_unlock(&sbi->lookup_lock);
}
spin_lock(&sbi->lookup_lock);
list_del_init(&ino->active);
spin_unlock(&sbi->lookup_lock);
}
static int autofs_dir_open(struct inode *inode, struct file *file)
@ -527,19 +504,22 @@ static struct dentry *autofs_lookup(struct inode *dir,
if (!autofs_oz_mode(sbi) && !IS_ROOT(dentry->d_parent))
return ERR_PTR(-ENOENT);
/* Mark entries in the root as mount triggers */
if (IS_ROOT(dentry->d_parent) &&
autofs_type_indirect(sbi->type))
__managed_dentry_set_managed(dentry);
ino = autofs_new_ino(sbi);
if (!ino)
return ERR_PTR(-ENOMEM);
spin_lock(&sbi->lookup_lock);
spin_lock(&dentry->d_lock);
/* Mark entries in the root as mount triggers */
if (IS_ROOT(dentry->d_parent) &&
autofs_type_indirect(sbi->type))
__managed_dentry_set_managed(dentry);
dentry->d_fsdata = ino;
ino->dentry = dentry;
autofs_add_active(dentry);
list_add(&ino->active, &sbi->active_list);
spin_unlock(&sbi->lookup_lock);
spin_unlock(&dentry->d_lock);
}
return NULL;
}