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VFS: move mnt_want_write() and locking into lookup_open()

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The mnt_want_write() call and the parent inode locking in
open_last_lookups() are only needed for lookup_open().  So we can move
them and all the got_write handling into lookup_open().

Note that we need to also check create_error when determining whether to
unlock shared or not, as O_CREAT can be cleared, but create_error is
only set of O_CREAT was set.

The fsnotify calls come too as they must be in the locked region.

Also use the existing dir_inode uniformly for dir->d_inode.

This is a step towards exporting an better "open/create" interface to nfsd.

Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jori Koolstra <jkoolstra@xs4all.nl>
Signed-off-by: NeilBrown <neil@brown.name>
Link: https://patch.msgid.link/20260714230534.776886-2-neilb@ownmail.net
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
This commit is contained in:
NeilBrown
2026-07-15 09:04:12 +10:00
committed by Christian Brauner
parent dc59e4fea9
commit ddb6e6c72a
1 changed files with 41 additions and 36 deletions
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77
fs/namei.c
View File

@@ -4403,7 +4403,7 @@ static struct dentry *atomic_open(const struct path *path, struct dentry *dentry
*/
static struct dentry *lookup_open(struct nameidata *nd, struct file *file,
const struct open_flags *op,
bool got_write, struct delegated_inode *delegated_inode)
struct delegated_inode *delegated_inode)
{
struct mnt_idmap *idmap;
struct dentry *dir = nd->path.dentry;
@@ -4412,9 +4412,25 @@ static struct dentry *lookup_open(struct nameidata *nd, struct file *file,
struct dentry *dentry;
int error, create_error = 0;
umode_t mode = op->mode;
bool got_write = false;
if (unlikely(IS_DEADDIR(dir_inode)))
return ERR_PTR(-ENOENT);
if (open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) {
got_write = !mnt_want_write(nd->path.mnt);
/*
* do _not_ fail yet - we might not need that or fail with
* a different error; let lookup_open() decide; we'll be
* dropping this one anyway.
*/
}
if (open_flag & O_CREAT)
inode_lock(dir_inode);
else
inode_lock_shared(dir_inode);
if (unlikely(IS_DEADDIR(dir_inode))) {
dentry = ERR_PTR(-ENOENT);
goto out;
}
file->f_mode &= ~FMODE_CREATED;
dentry = d_lookup(dir, &nd->last);
@@ -4422,7 +4438,7 @@ static struct dentry *lookup_open(struct nameidata *nd, struct file *file,
if (!dentry) {
dentry = d_alloc_parallel(dir, &nd->last);
if (IS_ERR(dentry))
return dentry;
goto out;
}
if (d_in_lookup(dentry))
break;
@@ -4438,7 +4454,7 @@ static struct dentry *lookup_open(struct nameidata *nd, struct file *file,
}
if (dentry->d_inode) {
/* Cached positive dentry: will open in f_op->open */
return dentry;
goto out;
}
if (open_flag & O_CREAT)
@@ -4459,7 +4475,7 @@ static struct dentry *lookup_open(struct nameidata *nd, struct file *file,
if (open_flag & O_CREAT) {
if (open_flag & O_EXCL)
open_flag &= ~O_TRUNC;
mode = vfs_prepare_mode(idmap, dir->d_inode, mode, mode, mode);
mode = vfs_prepare_mode(idmap, dir_inode, mode, mode, mode);
if (likely(got_write))
create_error = may_o_create(idmap, &nd->path,
dentry, mode);
@@ -4474,7 +4490,7 @@ static struct dentry *lookup_open(struct nameidata *nd, struct file *file,
dentry = atomic_open(&nd->path, dentry, file, open_flag, mode);
if (unlikely(create_error) && dentry == ERR_PTR(-ENOENT))
dentry = ERR_PTR(create_error);
return dentry;
goto out;
}
if (d_in_lookup(dentry)) {
@@ -4514,11 +4530,27 @@ static struct dentry *lookup_open(struct nameidata *nd, struct file *file,
error = create_error;
goto out_dput;
}
out:
if (!IS_ERR(dentry)) {
if (file->f_mode & FMODE_CREATED)
fsnotify_create(dir_inode, dentry);
if (file->f_mode & FMODE_OPENED)
fsnotify_open(file);
}
if ((open_flag & O_CREAT) || create_error)
inode_unlock(dir_inode);
else
inode_unlock_shared(dir_inode);
if (got_write)
mnt_drop_write(nd->path.mnt);
return dentry;
out_dput:
dput(dentry);
return ERR_PTR(error);
dentry = ERR_PTR(error);
goto out;
}
static inline bool trailing_slashes(struct nameidata *nd)
@@ -4561,9 +4593,7 @@ static const char *open_last_lookups(struct nameidata *nd,
struct file *file, const struct open_flags *op)
{
struct delegated_inode delegated_inode = { };
struct dentry *dir = nd->path.dentry;
int open_flag = op->open_flag;
bool got_write = false;
struct dentry *dentry;
const char *res;
@@ -4593,32 +4623,7 @@ static const char *open_last_lookups(struct nameidata *nd,
}
}
retry:
if (open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) {
got_write = !mnt_want_write(nd->path.mnt);
/*
* do _not_ fail yet - we might not need that or fail with
* a different error; let lookup_open() decide; we'll be
* dropping this one anyway.
*/
}
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, &delegated_inode);
if (!IS_ERR(dentry)) {
if (file->f_mode & FMODE_CREATED)
fsnotify_create(dir->d_inode, 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 (got_write)
mnt_drop_write(nd->path.mnt);
dentry = lookup_open(nd, file, op, &delegated_inode);
if (IS_ERR(dentry)) {
if (is_delegated(&delegated_inode)) {