The VFS no longer needs the directory to be locked when performing
updates in the directory (create/remove/rename). We only lock
directories during these ops because the filesystem might expect that.
Some filesystems may not need it. Allow the filesystem to opt out by
setting no_dir_lock in inode_operations.
Signed-off-by: NeilBrown <neil@xxxxxxxxxx>
---
fs/namei.c | 75 ++++++++++++++++++++++++++++++++--------------
include/linux/fs.h | 1 +
2 files changed, 54 insertions(+), 22 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c
index 5c9279657b32..55ea67b4f891 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2001,7 +2001,8 @@ struct dentry *lookup_and_lock_hashed(struct qstr *last,
{
struct dentry *dentry;
- inode_lock_nested(base->d_inode, I_MUTEX_PARENT);
+ if (!d_inode(base)->i_op->no_dir_lock)
+ inode_lock_nested(base->d_inode, I_MUTEX_PARENT);
retry:
dentry = lookup_one_qstr(last, base, lookup_flags);
@@ -2011,7 +2012,8 @@ struct dentry *lookup_and_lock_hashed(struct qstr *last,
goto retry;
}
- if (IS_ERR(dentry))
+ if (IS_ERR(dentry) &&
+ !d_inode(base)->i_op->no_dir_lock)
inode_unlock(base->d_inode);
return dentry;
}
@@ -2066,11 +2068,13 @@ struct dentry *lookup_and_lock_noperm(struct qstr *last,
{
struct dentry *dentry;
- inode_lock_nested(base->d_inode, I_MUTEX_PARENT);
+ if (!d_inode(base)->i_op->no_dir_lock)
+ inode_lock_nested(base->d_inode, I_MUTEX_PARENT);
dentry = lookup_and_lock_noperm_locked(last, base, lookup_flags,
DLOCK_NORMAL);
- if (IS_ERR(dentry))
+ if (IS_ERR(dentry) &&
+ !d_inode(base)->i_op->no_dir_lock)
inode_unlock(base->d_inode);
return dentry;
}
@@ -2097,9 +2101,11 @@ struct dentry *lookup_and_lock_noperm_nested(struct qstr *last,
{
struct dentry *dentry;
- inode_lock_nested(base->d_inode, I_MUTEX_PARENT);
+ if (!d_inode(base)->i_op->no_dir_lock)
+ inode_lock_nested(base->d_inode, I_MUTEX_PARENT);
dentry = lookup_and_lock_noperm_locked(last, base, lookup_flags, class);
- if (IS_ERR(dentry))
+ if (IS_ERR(dentry) &&
+ !d_inode(base)->i_op->no_dir_lock)
inode_unlock(base->d_inode);
return dentry;
}
@@ -2160,9 +2166,12 @@ struct dentry *lookup_and_lock_killable(struct mnt_idmap *idmap,
struct dentry *dentry;
int err;
- err = down_write_killable_nested(&base->d_inode->i_rwsem, I_MUTEX_PARENT);
- if (err)
- return ERR_PTR(err);
+ if (!d_inode(base)->i_op->no_dir_lock) {
+ err = down_write_killable_nested(&base->d_inode->i_rwsem,
+ I_MUTEX_PARENT);
+ if (err)
+ return ERR_PTR(err);
+ }
err = lookup_one_common(idmap, last, base);
if (err < 0)
return ERR_PTR(err);
@@ -2176,7 +2185,8 @@ struct dentry *lookup_and_lock_killable(struct mnt_idmap *idmap,
return ERR_PTR(-ERESTARTSYS);
goto retry;
}
- if (IS_ERR(dentry))
+ if (IS_ERR(dentry) &&
+ !d_inode(base)->i_op->no_dir_lock)
inode_unlock(base->d_inode);
return dentry;
}
@@ -2205,7 +2215,8 @@ bool lock_and_check_dentry(struct dentry *child, struct dentry *parent)
}
/* get the child to balance with dentry_unlock() which puts it. */
dget(child);
- inode_lock_nested(d_inode(parent), I_MUTEX_PARENT);
+ if (!d_inode(parent)->i_op->no_dir_lock)
+ inode_lock_nested(d_inode(parent), I_MUTEX_PARENT);
return true;
}
EXPORT_SYMBOL(lock_and_check_dentry);
@@ -2230,7 +2241,8 @@ void dentry_unlock(struct dentry *dentry)
{
if (!IS_ERR(dentry)) {
d_lookup_done(dentry);
- inode_unlock(dentry->d_parent->d_inode);
+ if (!dentry->d_parent->d_inode->i_op->no_dir_lock)
+ inode_unlock(dentry->d_parent->d_inode);
dentry_unlock_dir_locked(dentry);
}
}
@@ -2342,9 +2354,11 @@ static struct dentry *lookup_slow(const struct qstr *name,
{
struct inode *inode = dir->d_inode;
struct dentry *res;
- inode_lock_shared(inode);
+ if (!inode->i_op->no_dir_lock)
+ inode_lock_shared(inode);
res = __lookup_slow(name, dir, flags);
- inode_unlock_shared(inode);
+ if (!inode->i_op->no_dir_lock)
+ inode_unlock_shared(inode);
return res;
}
@@ -3721,6 +3735,9 @@ static struct dentry *lock_two_directories(struct dentry *p1, struct dentry *p2)
*/
static struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
{
+ if (d_inode(p1)->i_op->no_dir_lock)
+ return NULL;
+
if (p1 == p2) {
inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
return NULL;
@@ -3735,6 +3752,9 @@ static struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
*/
static struct dentry *lock_rename_child(struct dentry *c1, struct dentry *p2)
{
+ if (d_inode(c1)->i_op->no_dir_lock)
+ return NULL;
+
if (READ_ONCE(c1->d_parent) == p2) {
/*
* hopefully won't need to touch ->s_vfs_rename_mutex at all.
@@ -3773,6 +3793,8 @@ static struct dentry *lock_rename_child(struct dentry *c1, struct dentry *p2)
static void unlock_rename(struct dentry *p1, struct dentry *p2)
{
+ if (d_inode(p1)->i_op->no_dir_lock)
+ return;
inode_unlock(p1->d_inode);
if (p1 != p2) {
inode_unlock(p2->d_inode);
@@ -3880,6 +3902,10 @@ static struct dentry *lock_ancestors(struct dentry *d1, struct dentry *d2)
{
struct dentry *locked, *ancestor;
+ if (!d_inode(d1)->i_op->no_dir_lock)
+ /* s_vfs_rename_mutex is being used, so skip this locking */
+ return NULL;
+
if (d1->d_parent == d2->d_parent)
/* Nothing to lock */
return NULL;
@@ -4194,6 +4220,7 @@ void dentry_unlock_rename(struct renamedata *rd)
renaming_unlock(rd->old_dir, rd->new_dir, rd->ancestor,
rd->old_dentry, rd->new_dentry);
+ if (!d_inode(rd->old_dir)->i_op->no_dir_lock)
unlock_rename(rd->old_dir, rd->new_dir);
dput(rd->old_dir);
@@ -4697,19 +4724,23 @@ static const char *open_last_lookups(struct nameidata *nd,
* dropping this one anyway.
*/
}
- if (open_flag & O_CREAT)
- inode_lock(dir->d_inode);
- else
- inode_lock_shared(dir->d_inode);
+ if (!d_inode(dir)->i_op->no_dir_lock) {
+ if (open_flag & O_CREAT)
+ inode_lock(dir->d_inode);
+ else
+ inode_lock_shared(dir->d_inode);
+ }
dentry = lookup_open(nd, file, op, got_write);
if (!IS_ERR(dentry)) {
if (file->f_mode & FMODE_OPENED)
fsnotify_open(file);
}
- if (open_flag & O_CREAT)
- inode_unlock(dir->d_inode);
- else
- inode_unlock_shared(dir->d_inode);
+ if (!d_inode(dir)->i_op->no_dir_lock) {
+ if (open_flag & O_CREAT)
+ inode_unlock(dir->d_inode);
+ else
+ inode_unlock_shared(dir->d_inode);
+ }
if (got_write)
mnt_drop_write(nd->path.mnt);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 6b4a1a1f4786..b213993c486a 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2225,6 +2225,7 @@ int wrap_directory_iterator(struct file *, struct dir_context *,
{ return wrap_directory_iterator(file, ctx, x); }
struct inode_operations {
+ bool no_dir_lock:1;
struct dentry * (*lookup) (struct inode *,struct dentry *, unsigned int);
const char * (*get_link) (struct dentry *, struct inode *, struct delayed_call *);
int (*permission) (struct mnt_idmap *, struct inode *, int);
--
2.49.0
