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Message-ID: <20250206054504.2950516-17-neilb@suse.de>
Date: Thu, 6 Feb 2025 16:42:53 +1100
From: NeilBrown <neilb@...e.de>
To: Alexander Viro <viro@...iv.linux.org.uk>,
Christian Brauner <brauner@...nel.org>,
Jan Kara <jack@...e.cz>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Jeff Layton <jlayton@...nel.org>,
Dave Chinner <david@...morbit.com>
Cc: linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH 16/19] VFS: add lookup_and_lock_rename()
lookup_and_lock_rename() combines locking and lookup for two names.
It uses the new lock_two_directories_shared() if that is appropriate for
the filesystem.
unlock_rename_shared() does either a shared unlock or an exclusive
unlock depending on how the filesystem wants rename to be handled.
lookup_and_lock_rename_one() and done_lookup_and_lock_rename() are
exported for other modules to use.
As a rename can continue asynchronously after the inode lock is dropped,
lock_two_directories() and lock_two_directories_shared() must ensure
that is not happening before looking at ->d_parent. This requires a
call to d_update_wait(). Note that is the dentry is locked for update
it must be a rename. It cannot be a create or a (successful) rmdir as
these dentries are not empty - except possibly the target directory, but
waiting for the rmdir there is still needed of course.
Signed-off-by: NeilBrown <neilb@...e.de>
---
fs/namei.c | 230 +++++++++++++++++++++++++++++++++++-------
include/linux/namei.h | 7 ++
2 files changed, 199 insertions(+), 38 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c
index c7b7445c770e..771e9d7b620c 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3451,8 +3451,14 @@ static struct dentry *lock_two_directories(struct dentry *p1, struct dentry *p2)
{
struct dentry *p = p1, *q = p2, *r;
- while ((r = p->d_parent) != p2 && r != p)
+ /* Ensure d_update_wait() tests are safe - one barrier for all */
+ smp_mb();
+
+ d_update_wait(p, I_MUTEX_NORMAL);
+ while ((r = p->d_parent) != p2 && r != p) {
p = r;
+ d_update_wait(p, I_MUTEX_NORMAL);
+ }
if (r == p2) {
// p is a child of p2 and an ancestor of p1 or p1 itself
inode_lock_nested(p2->d_inode, I_MUTEX_PARENT);
@@ -3461,8 +3467,11 @@ static struct dentry *lock_two_directories(struct dentry *p1, struct dentry *p2)
}
// p is the root of connected component that contains p1
// p2 does not occur on the path from p to p1
- while ((r = q->d_parent) != p1 && r != p && r != q)
+ d_update_wait(q, I_MUTEX_NORMAL);
+ while ((r = q->d_parent) != p1 && r != p && r != q) {
q = r;
+ d_update_wait(q, I_MUTEX_NORMAL);
+ }
if (r == p1) {
// q is a child of p1 and an ancestor of p2 or p2 itself
inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
@@ -3479,6 +3488,46 @@ static struct dentry *lock_two_directories(struct dentry *p1, struct dentry *p2)
}
}
+static struct dentry *lock_two_directories_shared(struct dentry *p1, struct dentry *p2)
+{
+ struct dentry *p = p1, *q = p2, *r;
+
+ /* Ensure d_update_wait() tests are safe - one barrier for all */
+ smp_mb();
+
+ d_update_wait(p1, I_MUTEX_NORMAL);
+ while ((r = p->d_parent) != p2 && r != p) {
+ p = r;
+ d_update_wait(p, I_MUTEX_NORMAL);
+ }
+ if (r == p2) {
+ // p is a child of p2 and an ancestor of p1 or p1 itself
+ inode_lock_shared_nested(p2->d_inode, I_MUTEX_PARENT);
+ inode_lock_shared_nested(p1->d_inode, I_MUTEX_PARENT2);
+ return p;
+ }
+ // p is the root of connected component that contains p1
+ // p2 does not occur on the path from p to p1
+ d_update_wait(q, I_MUTEX_NORMAL);
+ while ((r = q->d_parent) != p1 && r != p && r != q) {
+ q = r;
+ d_update_wait(q, I_MUTEX_NORMAL);
+ }
+ if (r == p1) {
+ // q is a child of p1 and an ancestor of p2 or p2 itself
+ inode_lock_shared_nested(p1->d_inode, I_MUTEX_PARENT);
+ inode_lock_shared_nested(p2->d_inode, I_MUTEX_PARENT2);
+ return q;
+ } else if (likely(r == p)) {
+ // both p2 and p1 are descendents of p
+ inode_lock_shared_nested(p1->d_inode, I_MUTEX_PARENT);
+ inode_lock_shared_nested(p2->d_inode, I_MUTEX_PARENT2);
+ return NULL;
+ } else { // no common ancestor at the time we'd been called
+ return ERR_PTR(-EXDEV);
+ }
+}
+
/*
* p1 and p2 should be directories on the same fs.
*/
@@ -3494,6 +3543,134 @@ struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
}
EXPORT_SYMBOL(lock_rename);
+static void unlock_rename_shared(struct dentry *p1, struct dentry *p2)
+{
+ if (!(p1->d_inode->i_flags & S_ASYNC_RENAME))
+ unlock_rename(p1, p2);
+ else {
+ inode_unlock_shared(p1->d_inode);
+ if (p1 != p2) {
+ inode_unlock_shared(p2->d_inode);
+ mutex_unlock(&p1->d_sb->s_vfs_rename_mutex);
+ }
+ }
+}
+
+static int
+lookup_and_lock_rename(struct dentry *p1, struct dentry *p2,
+ struct dentry **d1p, struct dentry **d2p,
+ struct qstr *last1, struct qstr *last2,
+ unsigned int flags1, unsigned int flags2)
+{
+ struct dentry *p = NULL;
+ struct dentry *d1, *d2;
+ bool ok1, ok2;
+
+ if (p1->d_inode->i_flags & S_ASYNC_RENAME) {
+ if (p1 == p2) {
+ /* same parent - only one parent lock needed and
+ * no s_vfs_rename_mutex */
+ inode_lock_shared_nested(p1->d_inode, I_MUTEX_PARENT);
+ } else {
+ mutex_lock(&p1->d_sb->s_vfs_rename_mutex);
+
+ p = lock_two_directories_shared(p1, p2);
+ if (IS_ERR(p)) {
+ mutex_unlock(&p1->d_sb->s_vfs_rename_mutex);
+ return PTR_ERR(p);
+ }
+ }
+ } else
+ lock_rename(p1, p2);
+retry:
+ d1 = lookup_one_qstr(last1, p1, flags1);
+ if (IS_ERR(d1))
+ goto out_unlock_1;
+ d2 = lookup_one_qstr(last2, p2, flags2);
+ if (IS_ERR(d2))
+ goto out_unlock_2;
+
+ if (d1 == p) {
+ dput(d1); dput(d2);
+ unlock_rename_shared(p1, p2);
+ if (flags1 & LOOKUP_CREATE)
+ return -EINVAL;
+ else
+ return -ENOTEMPTY;
+ }
+
+ if (d2 == p) {
+ dput(d1); dput(d2);
+ unlock_rename_shared(p1, p2);
+ if (flags2 & LOOKUP_CREATE)
+ return -EINVAL;
+ else
+ return -ENOTEMPTY;
+ }
+
+ if (d1 < d2) {
+ ok1 = d_update_lock(d1, p1, last1, I_MUTEX_PARENT);
+ ok2 = d_update_lock(d2, p2, last2, I_MUTEX_PARENT2);
+ } else if (d1 > d2) {
+ ok2 = d_update_lock(d2, p2, last2, I_MUTEX_PARENT);
+ ok1 = d_update_lock(d1, p1, last1, I_MUTEX_PARENT2);
+ } else {
+ ok1 = ok2 = d_update_lock(d1, p1, last1, I_MUTEX_PARENT);
+ }
+ if (!ok1 || !ok2) {
+ if (ok1)
+ d_update_unlock(d1);
+ if (ok2 && d2 != d1)
+ d_update_unlock(d2);
+ dput(d1);
+ dput(d2);
+ goto retry;
+ }
+ *d1p = d1; *d2p = d2;
+ return 0;
+
+out_unlock_2:
+ dput(d1);
+ d1 = d2;
+out_unlock_1:
+ unlock_rename_shared(p1, p2);
+ return PTR_ERR(d1);
+}
+
+int lookup_and_lock_rename_one(struct dentry *p1, struct dentry *p2,
+ struct dentry **d1p, struct dentry **d2p,
+ const char *name1, int nlen1,
+ const char *name2, int nlen2,
+ unsigned int flags1, unsigned int flags2)
+{
+ struct qstr this1, this2;
+ int err;
+
+ err = lookup_one_common(&nop_mnt_idmap, name1, p1, nlen1, &this1);
+ if (err)
+ return err;
+ err = lookup_one_common(&nop_mnt_idmap, name2, p2, nlen2, &this2);
+ if (err)
+ return err;
+ return lookup_and_lock_rename(p1, p2, d1p, d2p, &this1, &this2,
+ flags1, flags2);
+}
+EXPORT_SYMBOL(lookup_and_lock_rename_one);
+
+void done_lookup_and_lock_rename(struct dentry *p1, struct dentry *p2,
+ struct dentry *d1, struct dentry *d2)
+{
+ d_lookup_done(d1);
+ d_lookup_done(d2);
+ d_update_unlock(d1);
+ if (d2 != d1)
+ d_update_unlock(d2);
+ unlock_rename_shared(p1, p2);
+ dput(d1);
+ dput(d2);
+}
+EXPORT_SYMBOL(done_lookup_and_lock_rename);
+
/*
* c1 and p2 should be on the same fs.
*/
@@ -5497,7 +5674,6 @@ int do_renameat2(int olddfd, struct filename *from, int newdfd,
{
struct renamedata rd;
struct dentry *old_dentry, *new_dentry;
- struct dentry *trap;
struct path old_path, new_path;
struct qstr old_last, new_last;
int old_type, new_type;
@@ -5548,51 +5724,33 @@ int do_renameat2(int olddfd, struct filename *from, int newdfd,
goto exit2;
retry_deleg:
- trap = lock_rename(new_path.dentry, old_path.dentry);
- if (IS_ERR(trap)) {
- error = PTR_ERR(trap);
+ error = lookup_and_lock_rename(old_path.dentry, new_path.dentry,
+ &old_dentry, &new_dentry,
+ &old_last, &new_last,
+ lookup_flags, lookup_flags | target_flags);
+ if (error)
goto exit_lock_rename;
- }
- old_dentry = lookup_one_qstr(&old_last, old_path.dentry,
- lookup_flags);
- error = PTR_ERR(old_dentry);
- if (IS_ERR(old_dentry))
- goto exit3;
- new_dentry = lookup_one_qstr(&new_last, new_path.dentry,
- lookup_flags | target_flags);
- error = PTR_ERR(new_dentry);
- if (IS_ERR(new_dentry))
- goto exit4;
if (flags & RENAME_EXCHANGE) {
if (!d_is_dir(new_dentry)) {
error = -ENOTDIR;
if (new_last.name[new_last.len])
- goto exit5;
+ goto exit_unlock;
}
}
/* unless the source is a directory trailing slashes give -ENOTDIR */
if (!d_is_dir(old_dentry)) {
error = -ENOTDIR;
if (old_last.name[old_last.len])
- goto exit5;
+ goto exit_unlock;
if (!(flags & RENAME_EXCHANGE) && new_last.name[new_last.len])
- goto exit5;
- }
- /* source should not be ancestor of target */
- error = -EINVAL;
- if (old_dentry == trap)
- goto exit5;
- /* target should not be an ancestor of source */
- if (!(flags & RENAME_EXCHANGE))
- error = -ENOTEMPTY;
- if (new_dentry == trap)
- goto exit5;
+ goto exit_unlock;
+ }
error = security_path_rename(&old_path, old_dentry,
&new_path, new_dentry, flags);
if (error)
- goto exit5;
+ goto exit_unlock;
rd.old_dir = old_path.dentry->d_inode;
rd.old_dentry = old_dentry;
@@ -5603,13 +5761,9 @@ int do_renameat2(int olddfd, struct filename *from, int newdfd,
rd.delegated_inode = &delegated_inode;
rd.flags = flags;
error = vfs_rename(&rd);
-exit5:
- d_lookup_done(new_dentry);
- dput(new_dentry);
-exit4:
- dput(old_dentry);
-exit3:
- unlock_rename(new_path.dentry, old_path.dentry);
+exit_unlock:
+ done_lookup_and_lock_rename(new_path.dentry, old_path.dentry,
+ new_dentry, old_dentry);
exit_lock_rename:
if (delegated_inode) {
error = break_deleg_wait(&delegated_inode);
diff --git a/include/linux/namei.h b/include/linux/namei.h
index 72e351640406..8ef7aa6ed64c 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -104,6 +104,13 @@ extern int follow_up(struct path *);
extern struct dentry *lock_rename(struct dentry *, struct dentry *);
extern struct dentry *lock_rename_child(struct dentry *, struct dentry *);
extern void unlock_rename(struct dentry *, struct dentry *);
+int lookup_and_lock_rename_one(struct dentry *p1, struct dentry *p2,
+ struct dentry **d1p, struct dentry **d2p,
+ const char *name1, int nlen1,
+ const char *name2, int nlen2,
+ unsigned int flags1, unsigned int flags2);
+void done_lookup_and_lock_rename(struct dentry *p1, struct dentry *p2,
+ struct dentry *d1, struct dentry *d2);
/**
* mode_strip_umask - handle vfs umask stripping
--
2.47.1
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