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Message-ID: <20250812235228.3072318-9-neil@brown.name>
Date: Tue, 12 Aug 2025 12:25:11 +1000
From: NeilBrown <neil@...wn.name>
To: Alexander Viro <viro@...iv.linux.org.uk>,
Christian Brauner <brauner@...nel.org>,
Jan Kara <jack@...e.cz>
Cc: David Howells <dhowells@...hat.com>,
Marc Dionne <marc.dionne@...istor.com>,
Xiubo Li <xiubli@...hat.com>,
Ilya Dryomov <idryomov@...il.com>,
Tyler Hicks <code@...icks.com>,
Miklos Szeredi <miklos@...redi.hu>,
Richard Weinberger <richard@....at>,
Anton Ivanov <anton.ivanov@...bridgegreys.com>,
Johannes Berg <johannes@...solutions.net>,
Trond Myklebust <trondmy@...nel.org>,
Anna Schumaker <anna@...nel.org>,
Chuck Lever <chuck.lever@...cle.com>,
Jeff Layton <jlayton@...nel.org>,
Amir Goldstein <amir73il@...il.com>,
Steve French <sfrench@...ba.org>,
Namjae Jeon <linkinjeon@...nel.org>,
Carlos Maiolino <cem@...nel.org>,
linux-fsdevel@...r.kernel.org,
linux-afs@...ts.infradead.org,
netfs@...ts.linux.dev,
ceph-devel@...r.kernel.org,
ecryptfs@...r.kernel.org,
linux-um@...ts.infradead.org,
linux-nfs@...r.kernel.org,
linux-unionfs@...r.kernel.org,
linux-cifs@...r.kernel.org,
linux-xfs@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH 08/11] VFS: allow d_splice_alias() and d_add() to work on hashed dentries.
Proposed locking changes will require a dentry to remain hashed during
all directory operations which are currently protected by i_rwsem, or
for there to be a controlled transition from one hashed dentry to
another which maintains the lock - which will then be on the dentry.
The current practice of dropping (unhashing) a dentry before calling
d_splice_alias() and d_add() defeats this need.
This patch changes d_splice_alias() and d_add() to accept a hashed
dentry and to only drop it when necessary immediately before an
alternate dentry is hashed. These functions will, in a subsequent patch,
transfer the dentry locking across so that the name remains locked in
the directory.
Signed-off-by: NeilBrown <neil@...wn.name>
---
Documentation/filesystems/vfs.rst | 4 ++--
fs/ceph/file.c | 2 --
fs/ceph/inode.c | 3 ---
fs/dcache.c | 8 +++++---
fs/fuse/dir.c | 1 -
fs/hostfs/hostfs_kern.c | 1 -
fs/nfs/dir.c | 5 +----
fs/nfs/nfs4proc.c | 1 -
fs/smb/client/dir.c | 1 -
9 files changed, 8 insertions(+), 18 deletions(-)
diff --git a/Documentation/filesystems/vfs.rst b/Documentation/filesystems/vfs.rst
index 486a91633474..642dd6afb139 100644
--- a/Documentation/filesystems/vfs.rst
+++ b/Documentation/filesystems/vfs.rst
@@ -580,8 +580,8 @@ otherwise noted.
dentry before the first mkdir returns.
If there is any chance this could happen, then the new inode
- should be d_drop()ed and attached with d_splice_alias(). The
- returned dentry (if any) should be returned by ->mkdir().
+ should be attached with d_splice_alias(). The returned dentry
+ (if any) should be returned by ->mkdir().
``rmdir``
called by the rmdir(2) system call. Only required if you want
diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index c02f100f8552..27eb1ac06177 100644
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -755,8 +755,6 @@ static int ceph_finish_async_create(struct inode *dir, struct inode *inode,
unlock_new_inode(inode);
}
if (d_in_lookup(dentry) || d_really_is_negative(dentry)) {
- if (!d_unhashed(dentry))
- d_drop(dentry);
dn = d_splice_alias(inode, dentry);
WARN_ON_ONCE(dn && dn != dentry);
}
diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
index fc543075b827..7acd6ac0d50f 100644
--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -1480,9 +1480,6 @@ static int splice_dentry(struct dentry **pdn, struct inode *in)
}
}
- /* dn must be unhashed */
- if (!d_unhashed(dn))
- d_drop(dn);
realdn = d_splice_alias(in, dn);
if (IS_ERR(realdn)) {
pr_err_client(cl, "error %ld %p inode %p ino %llx.%llx\n",
diff --git a/fs/dcache.c b/fs/dcache.c
index 60046ae23d51..0db256098adb 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -2709,7 +2709,11 @@ static inline void __d_add(struct dentry *dentry, struct inode *inode,
raw_write_seqcount_end(&dentry->d_seq);
fsnotify_update_flags(dentry);
}
- __d_rehash(dentry);
+ if (d_unhashed(dentry))
+ __d_rehash(dentry);
+ else if (inode && (dentry->d_flags &
+ (DCACHE_LRU_LIST|DCACHE_SHRINK_LIST)) == DCACHE_LRU_LIST)
+ this_cpu_dec(nr_dentry_negative);
if (dir)
end_dir_add(dir, n, d_wait);
spin_unlock(&dentry->d_lock);
@@ -2990,8 +2994,6 @@ struct dentry *d_splice_alias_ops(struct inode *inode, struct dentry *dentry,
if (IS_ERR(inode))
return ERR_CAST(inode);
- BUG_ON(!d_unhashed(dentry));
-
if (!inode)
goto out;
diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 2d817d7cab26..60e7763da8c8 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -834,7 +834,6 @@ static struct dentry *create_new_entry(struct mnt_idmap *idmap, struct fuse_moun
}
kfree(forget);
- d_drop(entry);
d = d_splice_alias(inode, entry);
if (IS_ERR(d))
return d;
diff --git a/fs/hostfs/hostfs_kern.c b/fs/hostfs/hostfs_kern.c
index 01e516175bcd..8e51fc623301 100644
--- a/fs/hostfs/hostfs_kern.c
+++ b/fs/hostfs/hostfs_kern.c
@@ -700,7 +700,6 @@ static struct dentry *hostfs_mkdir(struct mnt_idmap *idmap, struct inode *ino,
dentry = ERR_PTR(err);
} else {
inode = hostfs_iget(dentry->d_sb, file);
- d_drop(dentry);
dentry = d_splice_alias(inode, dentry);
}
__putname(file);
diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index d81217923936..250a826d5480 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -2136,7 +2136,6 @@ int nfs_atomic_open(struct inode *dir, struct dentry *dentry,
err = PTR_ERR(inode);
trace_nfs_atomic_open_exit(dir, ctx, open_flags, err);
put_nfs_open_context(ctx);
- d_drop(dentry);
switch (err) {
case -ENOENT:
d_splice_alias(NULL, dentry);
@@ -2157,6 +2156,7 @@ int nfs_atomic_open(struct inode *dir, struct dentry *dentry,
default:
break;
}
+ d_drop(dentry);
goto out;
}
file->f_mode |= FMODE_CAN_ODIRECT;
@@ -2304,8 +2304,6 @@ nfs_add_or_obtain(struct dentry *dentry, struct nfs_fh *fhandle,
struct dentry *d;
int error;
- d_drop(dentry);
-
if (fhandle->size == 0) {
error = NFS_PROTO(dir)->lookup(dir, dentry, &dentry->d_name,
fhandle, fattr);
@@ -2652,7 +2650,6 @@ nfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
old_dentry, dentry);
trace_nfs_link_enter(inode, dir, dentry);
- d_drop(dentry);
if (S_ISREG(inode->i_mode))
nfs_sync_inode(inode);
error = NFS_PROTO(dir)->link(inode, dir, &dentry->d_name);
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 7d2b67e06cc3..d8739c286a99 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -3175,7 +3175,6 @@ static int _nfs4_open_and_get_state(struct nfs4_opendata *opendata,
dentry = opendata->dentry;
if (d_really_is_negative(dentry)) {
struct dentry *alias;
- d_drop(dentry);
alias = d_splice_alias(igrab(state->inode), dentry);
/* d_splice_alias() can't fail here - it's a non-directory */
if (alias) {
diff --git a/fs/smb/client/dir.c b/fs/smb/client/dir.c
index 5223edf6d11a..8cbc284c5005 100644
--- a/fs/smb/client/dir.c
+++ b/fs/smb/client/dir.c
@@ -439,7 +439,6 @@ static int cifs_do_create(struct inode *inode, struct dentry *direntry, unsigned
goto out_err;
}
- d_drop(direntry);
d_add(direntry, newinode);
out:
--
2.50.0.107.gf914562f5916.dirty
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