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Message-ID: <20250217053727.3368579-4-neilb@suse.de>
Date: Mon, 17 Feb 2025 16:30:05 +1100
From: NeilBrown <neilb@...e.de>
To: Christian Brauner <brauner@...nel.org>,
Alexander Viro <viro@...iv.linux.org.uk>,
Jan Kara <jack@...e.cz>
Cc: linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH 3/3] VFS: Change vfs_mkdir() to return the dentry.
vfs_mkdir() does not currently guarantee to leave the child dentry
hashed or make it positive on success. It may leave it unhashed and
negative and then the caller needs to perform a lookup to find the
target dentry, if it needs it.
This patch changes vfs_mkdir() to return the dentry provided by the
filesystems which is hashed and positive when provided. This reduces
the need for lookup code which is now included in vfs_mkdir() rather
than at various call-sites. The included lookup does not include the
permission check that some of the existing code included in e.g.
lookup_one_len(). This should not be necessary for lookup up a
directory which has just be successfully created.
If a different dentry is returned, the first one is put. If necessary
the fact that it is new can be determined by comparing pointers. A new
dentry will certainly have a new pointer (as the old is put after the
new is obtained).
The dentry returned by vfs_mkdir(), when not an error, *is* now
guaranteed to be hashed and positive.
A few callers do not need the dentry, but will now sometimes perform the
lookup anyway. This should be cheap except possibly in the case of cifs.
Signed-off-by: NeilBrown <neilb@...e.de>
---
drivers/base/devtmpfs.c | 7 ++--
fs/cachefiles/namei.c | 10 +++---
fs/ecryptfs/inode.c | 14 +++++---
fs/init.c | 7 ++--
fs/namei.c | 70 +++++++++++++++++++++++++++++++---------
fs/nfsd/nfs4recover.c | 7 ++--
fs/nfsd/vfs.c | 28 +++++-----------
fs/overlayfs/dir.c | 37 +++------------------
fs/overlayfs/overlayfs.h | 15 ++++-----
fs/overlayfs/super.c | 7 ++--
fs/smb/server/vfs.c | 31 ++++++------------
fs/xfs/scrub/orphanage.c | 9 +++---
include/linux/fs.h | 4 +--
13 files changed, 121 insertions(+), 125 deletions(-)
diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c
index c9e34842139f..8ec756b5dec4 100644
--- a/drivers/base/devtmpfs.c
+++ b/drivers/base/devtmpfs.c
@@ -160,18 +160,17 @@ static int dev_mkdir(const char *name, umode_t mode)
{
struct dentry *dentry;
struct path path;
- int err;
dentry = kern_path_create(AT_FDCWD, name, &path, LOOKUP_DIRECTORY);
if (IS_ERR(dentry))
return PTR_ERR(dentry);
- err = vfs_mkdir(&nop_mnt_idmap, d_inode(path.dentry), dentry, mode);
- if (!err)
+ dentry = vfs_mkdir(&nop_mnt_idmap, d_inode(path.dentry), dentry, mode);
+ if (!IS_ERR(dentry))
/* mark as kernel-created inode */
d_inode(dentry)->i_private = &thread;
done_path_create(&path, dentry);
- return err;
+ return PTR_ERR_OR_ZERO(dentry);
}
static int create_path(const char *nodepath)
diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
index 7cf59713f0f7..8a8337d1be05 100644
--- a/fs/cachefiles/namei.c
+++ b/fs/cachefiles/namei.c
@@ -95,7 +95,6 @@ struct dentry *cachefiles_get_directory(struct cachefiles_cache *cache,
/* search the current directory for the element name */
inode_lock_nested(d_inode(dir), I_MUTEX_PARENT);
-retry:
ret = cachefiles_inject_read_error();
if (ret == 0)
subdir = lookup_one_len(dirname, dir, strlen(dirname));
@@ -128,10 +127,11 @@ struct dentry *cachefiles_get_directory(struct cachefiles_cache *cache,
ret = security_path_mkdir(&path, subdir, 0700);
if (ret < 0)
goto mkdir_error;
- ret = cachefiles_inject_write_error();
- if (ret == 0)
- ret = vfs_mkdir(&nop_mnt_idmap, d_inode(dir), subdir, 0700);
- if (ret < 0) {
+ subdir = ERR_PTR(cachefiles_inject_write_error());
+ if (!IS_ERR(subdir))
+ subdir = vfs_mkdir(&nop_mnt_idmap, d_inode(dir), subdir, 0700);
+ ret = PTR_ERR(subdir);
+ if (IS_ERR(subdir)) {
trace_cachefiles_vfs_error(NULL, d_inode(dir), ret,
cachefiles_trace_mkdir_error);
goto mkdir_error;
diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
index 6315dd194228..51a5c54eb740 100644
--- a/fs/ecryptfs/inode.c
+++ b/fs/ecryptfs/inode.c
@@ -511,10 +511,16 @@ static struct dentry *ecryptfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
struct inode *lower_dir;
rc = lock_parent(dentry, &lower_dentry, &lower_dir);
- if (!rc)
- rc = vfs_mkdir(&nop_mnt_idmap, lower_dir,
- lower_dentry, mode);
- if (rc || d_really_is_negative(lower_dentry))
+ if (rc)
+ goto out;
+
+ lower_dentry = vfs_mkdir(&nop_mnt_idmap, lower_dir,
+ lower_dentry, mode);
+ rc = PTR_ERR(lower_dentry);
+ if (IS_ERR(lower_dentry))
+ goto out;
+ rc = 0;
+ if (d_unhashed(lower_dentry))
goto out;
rc = ecryptfs_interpose(lower_dentry, dentry, dir->i_sb);
if (rc)
diff --git a/fs/init.c b/fs/init.c
index e9387b6c4f30..eef5124885e3 100644
--- a/fs/init.c
+++ b/fs/init.c
@@ -230,9 +230,12 @@ int __init init_mkdir(const char *pathname, umode_t mode)
return PTR_ERR(dentry);
mode = mode_strip_umask(d_inode(path.dentry), mode);
error = security_path_mkdir(&path, dentry, mode);
- if (!error)
- error = vfs_mkdir(mnt_idmap(path.mnt), path.dentry->d_inode,
+ if (!error) {
+ dentry = vfs_mkdir(mnt_idmap(path.mnt), path.dentry->d_inode,
dentry, mode);
+ if (IS_ERR(dentry))
+ error = PTR_ERR(dentry);
+ }
done_path_create(&path, dentry);
return error;
}
diff --git a/fs/namei.c b/fs/namei.c
index 19d5ea340a18..f76fee6df369 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -4132,7 +4132,8 @@ EXPORT_SYMBOL(kern_path_create);
void done_path_create(struct path *path, struct dentry *dentry)
{
- dput(dentry);
+ if (!IS_ERR(dentry))
+ dput(dentry);
inode_unlock(path->dentry->d_inode);
mnt_drop_write(path->mnt);
path_put(path);
@@ -4278,7 +4279,7 @@ SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, d
}
/**
- * vfs_mkdir - create directory
+ * vfs_mkdir - create directory returning correct dentry is possible
* @idmap: idmap of the mount the inode was found from
* @dir: inode of the parent directory
* @dentry: dentry of the child directory
@@ -4291,9 +4292,20 @@ SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, d
* care to map the inode according to @idmap before checking permissions.
* On non-idmapped mounts or if permission checking is to be performed on the
* raw inode simply pass @nop_mnt_idmap.
+ *
+ * In the event that the filesystem does not use the *@...try but leaves it
+ * negative or unhashes it and possibly splices a different one returning it,
+ * the original dentry is dput() and the alternate is returned.
+ *
+ * If the file-system reports success but leaves the dentry unhashed or
+ * negative, a lookup is performed and providing that is positive and
+ * a directory, it will be returned. If the lookup is not successful
+ * the original dentry is unhashed and returned.
+ *
+ * In case of an error the dentry is dput() and an ERR_PTR() is returned.
*/
-int vfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
- struct dentry *dentry, umode_t mode)
+struct dentry *vfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
+ struct dentry *dentry, umode_t mode)
{
int error;
unsigned max_links = dir->i_sb->s_max_links;
@@ -4301,30 +4313,54 @@ int vfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
error = may_create(idmap, dir, dentry);
if (error)
- return error;
+ goto err;
+ error = -EPERM;
if (!dir->i_op->mkdir)
- return -EPERM;
+ goto err;
mode = vfs_prepare_mode(idmap, dir, mode, S_IRWXUGO | S_ISVTX, 0);
error = security_inode_mkdir(dir, dentry, mode);
if (error)
- return error;
+ goto err;
+ error = -EMLINK;
if (max_links && dir->i_nlink >= max_links)
- return -EMLINK;
+ goto err;
de = dir->i_op->mkdir(idmap, dir, dentry, mode);
+ error = PTR_ERR(de);
if (IS_ERR(de))
- return PTR_ERR(de);
+ goto err;
+ if (!de && (d_unhashed(dentry) || d_is_negative(dentry))) {
+ /* A few filesystems leave the dentry negative on success,
+ * currently cifs(with posix extensions), kernfs, tracefs, hostfs.
+ * They rely on a subsequent lookup which we perform here.
+ */
+ const struct qstr *d_name = (void*)&dentry->d_name;
+ de = lookup_dcache(d_name, dentry->d_parent, 0);
+ if (!de)
+ de = __lookup_slow(d_name, dentry->d_parent, 0);
+ if (IS_ERR(de))
+ de = NULL;
+ else if (unlikely(d_is_negative(de) || !d_is_dir(de))) {
+ dput(de);
+ de = NULL;
+ }
+ if (!de)
+ /* Ensure caller can easily detect that dentry is not useful */
+ d_drop(dentry);
+ }
if (de) {
- fsnotify_mkdir(dir, de);
- /* Cannot return de yet */
- dput(de);
- } else
- fsnotify_mkdir(dir, dentry);
+ dput(dentry);
+ dentry = de;
+ }
+ fsnotify_mkdir(dir, dentry);
+ return dentry;
- return 0;
+err:
+ dput(dentry);
+ return ERR_PTR(error);
}
EXPORT_SYMBOL(vfs_mkdir);
@@ -4344,8 +4380,10 @@ int do_mkdirat(int dfd, struct filename *name, umode_t mode)
error = security_path_mkdir(&path, dentry,
mode_strip_umask(path.dentry->d_inode, mode));
if (!error) {
- error = vfs_mkdir(mnt_idmap(path.mnt), path.dentry->d_inode,
+ dentry = vfs_mkdir(mnt_idmap(path.mnt), path.dentry->d_inode,
dentry, mode);
+ if (IS_ERR(dentry))
+ error = PTR_ERR(dentry);
}
done_path_create(&path, dentry);
if (retry_estale(error, lookup_flags)) {
diff --git a/fs/nfsd/nfs4recover.c b/fs/nfsd/nfs4recover.c
index 28f4d5311c40..c1d9bd07285f 100644
--- a/fs/nfsd/nfs4recover.c
+++ b/fs/nfsd/nfs4recover.c
@@ -233,9 +233,12 @@ nfsd4_create_clid_dir(struct nfs4_client *clp)
* as well be forgiving and just succeed silently.
*/
goto out_put;
- status = vfs_mkdir(&nop_mnt_idmap, d_inode(dir), dentry, S_IRWXU);
+ dentry = vfs_mkdir(&nop_mnt_idmap, d_inode(dir), dentry, S_IRWXU);
+ if (IS_ERR(dentry))
+ status = PTR_ERR(dentry);
out_put:
- dput(dentry);
+ if (!status)
+ dput(dentry);
out_unlock:
inode_unlock(d_inode(dir));
if (status == 0) {
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 29cb7b812d71..205b07f21e8d 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1461,7 +1461,7 @@ nfsd_create_locked(struct svc_rqst *rqstp, struct svc_fh *fhp,
struct inode *dirp;
struct iattr *iap = attrs->na_iattr;
__be32 err;
- int host_err;
+ int host_err = 0;
dentry = fhp->fh_dentry;
dirp = d_inode(dentry);
@@ -1488,26 +1488,13 @@ nfsd_create_locked(struct svc_rqst *rqstp, struct svc_fh *fhp,
nfsd_check_ignore_resizing(iap);
break;
case S_IFDIR:
- host_err = vfs_mkdir(&nop_mnt_idmap, dirp, dchild, iap->ia_mode);
- if (!host_err && unlikely(d_unhashed(dchild))) {
- struct dentry *d;
- d = lookup_one_len(dchild->d_name.name,
- dchild->d_parent,
- dchild->d_name.len);
- if (IS_ERR(d)) {
- host_err = PTR_ERR(d);
- break;
- }
- if (unlikely(d_is_negative(d))) {
- dput(d);
- err = nfserr_serverfault;
- goto out;
- }
+ dchild = vfs_mkdir(&nop_mnt_idmap, dirp, dchild, iap->ia_mode);
+ if (IS_ERR(dchild))
+ host_err = PTR_ERR(dchild);
+ else if (unlikely(dchild != resfhp->fh_dentry)) {
dput(resfhp->fh_dentry);
- resfhp->fh_dentry = dget(d);
+ resfhp->fh_dentry = dget(dchild);
err = fh_update(resfhp);
- dput(dchild);
- dchild = d;
if (err)
goto out;
}
@@ -1530,7 +1517,8 @@ nfsd_create_locked(struct svc_rqst *rqstp, struct svc_fh *fhp,
err = nfsd_create_setattr(rqstp, fhp, resfhp, attrs);
out:
- dput(dchild);
+ if (!IS_ERR(dchild))
+ dput(dchild);
return err;
out_nfserr:
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index 21c3aaf7b274..fe493f3ed6b6 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -138,37 +138,6 @@ int ovl_cleanup_and_whiteout(struct ovl_fs *ofs, struct inode *dir,
goto out;
}
-int ovl_mkdir_real(struct ovl_fs *ofs, struct inode *dir,
- struct dentry **newdentry, umode_t mode)
-{
- int err;
- struct dentry *d, *dentry = *newdentry;
-
- err = ovl_do_mkdir(ofs, dir, dentry, mode);
- if (err)
- return err;
-
- if (likely(!d_unhashed(dentry)))
- return 0;
-
- /*
- * vfs_mkdir() may succeed and leave the dentry passed
- * to it unhashed and negative. If that happens, try to
- * lookup a new hashed and positive dentry.
- */
- d = ovl_lookup_upper(ofs, dentry->d_name.name, dentry->d_parent,
- dentry->d_name.len);
- if (IS_ERR(d)) {
- pr_warn("failed lookup after mkdir (%pd2, err=%i).\n",
- dentry, err);
- return PTR_ERR(d);
- }
- dput(dentry);
- *newdentry = d;
-
- return 0;
-}
-
struct dentry *ovl_create_real(struct ovl_fs *ofs, struct inode *dir,
struct dentry *newdentry, struct ovl_cattr *attr)
{
@@ -191,7 +160,8 @@ struct dentry *ovl_create_real(struct ovl_fs *ofs, struct inode *dir,
case S_IFDIR:
/* mkdir is special... */
- err = ovl_mkdir_real(ofs, dir, &newdentry, attr->mode);
+ newdentry = ovl_do_mkdir(ofs, dir, newdentry, attr->mode);
+ err = PTR_ERR_OR_ZERO(newdentry);
break;
case S_IFCHR:
@@ -219,7 +189,8 @@ struct dentry *ovl_create_real(struct ovl_fs *ofs, struct inode *dir,
}
out:
if (err) {
- dput(newdentry);
+ if (!IS_ERR(newdentry))
+ dput(newdentry);
return ERR_PTR(err);
}
return newdentry;
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 0021e2025020..6f2f8f4cfbbc 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -241,13 +241,14 @@ static inline int ovl_do_create(struct ovl_fs *ofs,
return err;
}
-static inline int ovl_do_mkdir(struct ovl_fs *ofs,
- struct inode *dir, struct dentry *dentry,
- umode_t mode)
+static inline struct dentry *ovl_do_mkdir(struct ovl_fs *ofs,
+ struct inode *dir,
+ struct dentry *dentry,
+ umode_t mode)
{
- int err = vfs_mkdir(ovl_upper_mnt_idmap(ofs), dir, dentry, mode);
- pr_debug("mkdir(%pd2, 0%o) = %i\n", dentry, mode, err);
- return err;
+ dentry = vfs_mkdir(ovl_upper_mnt_idmap(ofs), dir, dentry, mode);
+ pr_debug("mkdir(%pd2, 0%o) = %i\n", dentry, mode, PTR_ERR_OR_ZERO(dentry));
+ return dentry;
}
static inline int ovl_do_mknod(struct ovl_fs *ofs,
@@ -838,8 +839,6 @@ struct ovl_cattr {
#define OVL_CATTR(m) (&(struct ovl_cattr) { .mode = (m) })
-int ovl_mkdir_real(struct ovl_fs *ofs, struct inode *dir,
- struct dentry **newdentry, umode_t mode);
struct dentry *ovl_create_real(struct ovl_fs *ofs,
struct inode *dir, struct dentry *newdentry,
struct ovl_cattr *attr);
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 86ae6f6da36b..a381765802e9 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -327,9 +327,10 @@ static struct dentry *ovl_workdir_create(struct ovl_fs *ofs,
goto retry;
}
- err = ovl_mkdir_real(ofs, dir, &work, attr.ia_mode);
- if (err)
- goto out_dput;
+ work = ovl_do_mkdir(ofs, dir, work, attr.ia_mode);
+ err = PTR_ERR(work);
+ if (IS_ERR(work))
+ goto out_err;
/* Weird filesystem returning with hashed negative (kernfs)? */
err = -EINVAL;
diff --git a/fs/smb/server/vfs.c b/fs/smb/server/vfs.c
index fe29acef5872..d682443b14ac 100644
--- a/fs/smb/server/vfs.c
+++ b/fs/smb/server/vfs.c
@@ -206,7 +206,7 @@ int ksmbd_vfs_mkdir(struct ksmbd_work *work, const char *name, umode_t mode)
{
struct mnt_idmap *idmap;
struct path path;
- struct dentry *dentry;
+ struct dentry *dentry, *d;
int err;
dentry = ksmbd_vfs_kern_path_create(work, name,
@@ -222,31 +222,18 @@ int ksmbd_vfs_mkdir(struct ksmbd_work *work, const char *name, umode_t mode)
idmap = mnt_idmap(path.mnt);
mode |= S_IFDIR;
- err = vfs_mkdir(idmap, d_inode(path.dentry), dentry, mode);
- if (!err && d_unhashed(dentry)) {
- struct dentry *d;
-
- d = lookup_one(idmap, dentry->d_name.name, dentry->d_parent,
- dentry->d_name.len);
- if (IS_ERR(d)) {
- err = PTR_ERR(d);
- goto out_err;
- }
- if (unlikely(d_is_negative(d))) {
- dput(d);
- err = -ENOENT;
- goto out_err;
- }
-
+ d = dentry;
+ entry = vfs_mkdir(idmap, d_inode(path.dentry), dentry, mode);
+ err = PTR_ERR(dentry);
+ if (!IS_ERR(dentry) && dentry != d)
ksmbd_vfs_inherit_owner(work, d_inode(path.dentry), d_inode(d));
- dput(d);
- }
-out_err:
done_path_create(&path, dentry);
- if (err)
+ if (IS_ERR(dentry)) {
pr_err("mkdir(%s): creation failed (err:%d)\n", name, err);
- return err;
+ return err;
+ }
+ return 0;
}
static ssize_t ksmbd_vfs_getcasexattr(struct mnt_idmap *idmap,
diff --git a/fs/xfs/scrub/orphanage.c b/fs/xfs/scrub/orphanage.c
index c287c755f2c5..3537f3cca6d5 100644
--- a/fs/xfs/scrub/orphanage.c
+++ b/fs/xfs/scrub/orphanage.c
@@ -167,10 +167,11 @@ xrep_orphanage_create(
* directory to control access to a file we put in here.
*/
if (d_really_is_negative(orphanage_dentry)) {
- error = vfs_mkdir(&nop_mnt_idmap, root_inode, orphanage_dentry,
- 0750);
- if (error)
- goto out_dput_orphanage;
+ orphanage_dentry = vfs_mkdir(&nop_mnt_idmap, root_inode,
+ orphanage_dentry, 0750);
+ error = PTR_ERR(orphanage_dentry);
+ if (IS_ERR(orphanage_dentry))
+ goto out_unlock_root;
}
/* Not a directory? Bail out. */
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 45269608ee23..beae24bc990d 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1981,8 +1981,8 @@ bool inode_owner_or_capable(struct mnt_idmap *idmap,
*/
int vfs_create(struct mnt_idmap *, struct inode *,
struct dentry *, umode_t, bool);
-int vfs_mkdir(struct mnt_idmap *, struct inode *,
- struct dentry *, umode_t);
+struct dentry *vfs_mkdir(struct mnt_idmap *, struct inode *,
+ struct dentry *, umode_t);
int vfs_mknod(struct mnt_idmap *, struct inode *, struct dentry *,
umode_t, dev_t);
int vfs_symlink(struct mnt_idmap *, struct inode *,
--
2.47.1
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