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Message-ID: <20250206054504.2950516-4-neilb@suse.de>
Date: Thu, 6 Feb 2025 16:42:40 +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 03/19] VFS: use d_alloc_parallel() in lookup_one_qstr_excl() and rename it.
lookup_one_qstr_excl() is used for lookups prior to directory
modifications, whether create, unlink, rename, or whatever.
To prepare for allowing modification to happen in parallel, change
lookup_one_qstr_excl() to use d_alloc_parallel().
To reflect this, name is changed to lookup_one_qtr() - as the directory
may be locked shared.
If any for the "intent" LOOKUP flags are passed, the caller must ensure
d_lookup_done() is called at an appropriate time. If none are passed
then we can be sure ->lookup() will do a real lookup and d_lookup_done()
is called internally.
Signed-off-by: NeilBrown <neilb@...e.de>
---
fs/namei.c | 47 +++++++++++++++++++++++++------------------
fs/smb/server/vfs.c | 7 ++++---
include/linux/namei.h | 9 ++++++---
3 files changed, 37 insertions(+), 26 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c
index 5cdbd2eb4056..d684102d873d 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1665,15 +1665,13 @@ static struct dentry *lookup_dcache(const struct qstr *name,
}
/*
- * Parent directory has inode locked exclusive. This is one
- * and only case when ->lookup() gets called on non in-lookup
- * dentries - as the matter of fact, this only gets called
- * when directory is guaranteed to have no in-lookup children
- * at all.
+ * Parent directory has inode locked: exclusive or shared.
+ * If @flags contains any LOOKUP_INTENT_FLAGS then d_lookup_done()
+ * must be called after the intended operation is performed - or aborted.
*/
-struct dentry *lookup_one_qstr_excl(const struct qstr *name,
- struct dentry *base,
- unsigned int flags)
+struct dentry *lookup_one_qstr(const struct qstr *name,
+ struct dentry *base,
+ unsigned int flags)
{
struct dentry *dentry = lookup_dcache(name, base, flags);
struct dentry *old;
@@ -1686,18 +1684,25 @@ struct dentry *lookup_one_qstr_excl(const struct qstr *name,
if (unlikely(IS_DEADDIR(dir)))
return ERR_PTR(-ENOENT);
- dentry = d_alloc(base, name);
- if (unlikely(!dentry))
+ dentry = d_alloc_parallel(base, name);
+ if (unlikely(IS_ERR_OR_NULL(dentry)))
return ERR_PTR(-ENOMEM);
+ if (!d_in_lookup(dentry))
+ /* Raced with another thread which did the lookup */
+ return dentry;
old = dir->i_op->lookup(dir, dentry, flags);
if (unlikely(old)) {
+ d_lookup_done(dentry);
dput(dentry);
dentry = old;
}
+ if ((flags & LOOKUP_INTENT_FLAGS) == 0)
+ /* ->lookup must have given final answer */
+ d_lookup_done(dentry);
return dentry;
}
-EXPORT_SYMBOL(lookup_one_qstr_excl);
+EXPORT_SYMBOL(lookup_one_qstr);
/**
* lookup_fast - do fast lockless (but racy) lookup of a dentry
@@ -2739,7 +2744,7 @@ static struct dentry *__kern_path_locked(int dfd, struct filename *name, struct
return ERR_PTR(-EINVAL);
}
inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT);
- d = lookup_one_qstr_excl(&last, path->dentry, 0);
+ d = lookup_one_qstr(&last, path->dentry, 0);
if (IS_ERR(d)) {
inode_unlock(path->dentry->d_inode);
path_put(path);
@@ -4078,8 +4083,8 @@ static struct dentry *filename_create(int dfd, struct filename *name,
if (last.name[last.len] && !want_dir)
create_flags = 0;
inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT);
- dentry = lookup_one_qstr_excl(&last, path->dentry,
- reval_flag | create_flags);
+ dentry = lookup_one_qstr(&last, path->dentry,
+ reval_flag | create_flags);
if (IS_ERR(dentry))
goto unlock;
@@ -4103,6 +4108,7 @@ static struct dentry *filename_create(int dfd, struct filename *name,
}
return dentry;
fail:
+ d_lookup_done(dentry);
dput(dentry);
dentry = ERR_PTR(error);
unlock:
@@ -4508,7 +4514,7 @@ int do_rmdir(int dfd, struct filename *name)
goto exit2;
inode_lock_nested(path.dentry->d_inode, I_MUTEX_PARENT);
- dentry = lookup_one_qstr_excl(&last, path.dentry, lookup_flags);
+ dentry = lookup_one_qstr(&last, path.dentry, lookup_flags);
error = PTR_ERR(dentry);
if (IS_ERR(dentry))
goto exit3;
@@ -4641,7 +4647,7 @@ int do_unlinkat(int dfd, struct filename *name)
goto exit2;
retry_deleg:
inode_lock_nested(path.dentry->d_inode, I_MUTEX_PARENT);
- dentry = lookup_one_qstr_excl(&last, path.dentry, lookup_flags);
+ dentry = lookup_one_qstr(&last, path.dentry, lookup_flags);
error = PTR_ERR(dentry);
if (!IS_ERR(dentry)) {
@@ -5231,8 +5237,8 @@ int do_renameat2(int olddfd, struct filename *from, int newdfd,
goto exit_lock_rename;
}
- old_dentry = lookup_one_qstr_excl(&old_last, old_path.dentry,
- lookup_flags);
+ old_dentry = lookup_one_qstr(&old_last, old_path.dentry,
+ lookup_flags);
error = PTR_ERR(old_dentry);
if (IS_ERR(old_dentry))
goto exit3;
@@ -5240,8 +5246,8 @@ int do_renameat2(int olddfd, struct filename *from, int newdfd,
error = -ENOENT;
if (d_is_negative(old_dentry))
goto exit4;
- new_dentry = lookup_one_qstr_excl(&new_last, new_path.dentry,
- lookup_flags | target_flags);
+ 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;
@@ -5292,6 +5298,7 @@ int do_renameat2(int olddfd, struct filename *from, int newdfd,
rd.flags = flags;
error = vfs_rename(&rd);
exit5:
+ d_lookup_done(new_dentry);
dput(new_dentry);
exit4:
dput(old_dentry);
diff --git a/fs/smb/server/vfs.c b/fs/smb/server/vfs.c
index 4e580bb7baf8..89b3823f6405 100644
--- a/fs/smb/server/vfs.c
+++ b/fs/smb/server/vfs.c
@@ -109,7 +109,7 @@ static int ksmbd_vfs_path_lookup_locked(struct ksmbd_share_config *share_conf,
}
inode_lock_nested(parent_path->dentry->d_inode, I_MUTEX_PARENT);
- d = lookup_one_qstr_excl(&last, parent_path->dentry, 0);
+ d = lookup_one_qstr(&last, parent_path->dentry, 0);
if (IS_ERR(d))
goto err_out;
@@ -726,8 +726,8 @@ int ksmbd_vfs_rename(struct ksmbd_work *work, const struct path *old_path,
ksmbd_fd_put(work, parent_fp);
}
- new_dentry = lookup_one_qstr_excl(&new_last, new_path.dentry,
- lookup_flags | LOOKUP_RENAME_TARGET);
+ new_dentry = lookup_one_qstr(&new_last, new_path.dentry,
+ lookup_flags | LOOKUP_RENAME_TARGET);
if (IS_ERR(new_dentry)) {
err = PTR_ERR(new_dentry);
goto out3;
@@ -771,6 +771,7 @@ int ksmbd_vfs_rename(struct ksmbd_work *work, const struct path *old_path,
ksmbd_debug(VFS, "vfs_rename failed err %d\n", err);
out4:
+ d_lookup_done(new_dentry);
dput(new_dentry);
out3:
dput(old_parent);
diff --git a/include/linux/namei.h b/include/linux/namei.h
index 8ec8fed3bce8..06bb3ea65beb 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -34,6 +34,9 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT};
#define LOOKUP_EXCL 0x0400 /* ... in exclusive creation */
#define LOOKUP_RENAME_TARGET 0x0800 /* ... in destination of rename() */
+#define LOOKUP_INTENT_FLAGS (LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_EXCL | \
+ LOOKUP_RENAME_TARGET)
+
/* internal use only */
#define LOOKUP_PARENT 0x0010
@@ -52,9 +55,9 @@ extern int path_pts(struct path *path);
extern int user_path_at(int, const char __user *, unsigned, struct path *);
-struct dentry *lookup_one_qstr_excl(const struct qstr *name,
- struct dentry *base,
- unsigned int flags);
+struct dentry *lookup_one_qstr(const struct qstr *name,
+ struct dentry *base,
+ unsigned int flags);
extern int kern_path(const char *, unsigned, struct path *);
extern struct dentry *kern_path_create(int, const char *, struct path *, unsigned int);
--
2.47.1
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