Re: [PATCH 06/06] 9p fid refcount: cleanup p9_fid_put calls

From: Tyler Hicks
Date: Mon Jun 13 2022 - 15:31:03 EST

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In reply to: Dominique Martinet: "[PATCH 06/06] 9p fid refcount: cleanup p9_fid_put calls"
Next in thread: Dominique Martinet: "Re: [PATCH 06/06] 9p fid refcount: cleanup p9_fid_put calls"
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On 2022-06-12 17:53:29, Dominique Martinet wrote:
> Simplify p9_fid_put cleanup path in many 9p functions since the function
> is noop on null or error fids.
>
> Also make the *_add_fid() helpers "steal" the fid by nulling its
> pointer, so put after them will be noop.
>
> This should lead to no change of behaviour

Another really nice cleanup. Only one small comment below.

>
> Signed-off-by: Dominique Martinet <asmadeus@xxxxxxxxxxxxx>
> ---
> fs/9p/fid.c | 24 +++++++++++------
> fs/9p/fid.h | 4 +--
> fs/9p/vfs_file.c | 5 ++--
> fs/9p/vfs_inode.c | 61 +++++++++++++++++-------------------------
> fs/9p/vfs_inode_dotl.c | 58 +++++++++++++--------------------------
> fs/9p/vfs_super.c | 2 +-
> 6 files changed, 64 insertions(+), 90 deletions(-)
>
> diff --git a/fs/9p/fid.c b/fs/9p/fid.c
> index d792499349c4..289a85eae2ae 100644
> --- a/fs/9p/fid.c
> +++ b/fs/9p/fid.c
> @@ -31,11 +31,15 @@ static inline void __add_fid(struct dentry *dentry, struct p9_fid *fid)
> * @fid: fid to add
> *
> */
> -void v9fs_fid_add(struct dentry *dentry, struct p9_fid *fid)
> +void v9fs_fid_add(struct dentry *dentry, struct p9_fid **pfid)
> {
> + struct p9_fid *fid = *pfid;
> +
> spin_lock(&dentry->d_lock);
> __add_fid(dentry, fid);
> spin_unlock(&dentry->d_lock);
> +
> + *pfid = NULL;
> }
>
> /**
> @@ -72,11 +76,15 @@ static struct p9_fid *v9fs_fid_find_inode(struct inode *inode, kuid_t uid)
> *
> */
>
> -void v9fs_open_fid_add(struct inode *inode, struct p9_fid *fid)
> +void v9fs_open_fid_add(struct inode *inode, struct p9_fid **pfid)
> {
> + struct p9_fid *fid = *pfid;
> +
> spin_lock(&inode->i_lock);
> hlist_add_head(&fid->ilist, (struct hlist_head *)&inode->i_private);
> spin_unlock(&inode->i_lock);
> +
> + *pfid = NULL;
> }
>
>
> @@ -189,13 +197,13 @@ static struct p9_fid *v9fs_fid_lookup_with_uid(struct dentry *dentry,
> else
> uname = v9ses->uname;
>
> - root_fid = p9_client_attach(v9ses->clnt, NULL, uname, uid,
> - v9ses->aname);
> - if (IS_ERR(root_fid))
> - return root_fid;
> + fid = p9_client_attach(v9ses->clnt, NULL, uname, uid,

To keep the readability benefits in my "9p: Track the root fid with its
own variable during lookups" patch, I think root_fid should be assigned
here and then used in the error check and return statement.

> + v9ses->aname);
> + if (IS_ERR(fid))
> + return fid;
>
> - p9_fid_get(root_fid);
> - v9fs_fid_add(dentry->d_sb->s_root, root_fid);
> + root_fid = p9_fid_get(fid);
> + v9fs_fid_add(dentry->d_sb->s_root, &fid);

root_fid should be used in the two lines above, too.

With these changes,

Reviewed-by: Tyler Hicks <tyhicks@xxxxxxxxxxxxxxxxxxx>

Tyler

> }
> /* If we are root ourself just return that */
> if (dentry->d_sb->s_root == dentry)
> diff --git a/fs/9p/fid.h b/fs/9p/fid.h
> index 3168dfad510e..8a4e8cd12ca2 100644
> --- a/fs/9p/fid.h
> +++ b/fs/9p/fid.h
> @@ -13,9 +13,9 @@ static inline struct p9_fid *v9fs_parent_fid(struct dentry *dentry)
> {
> return v9fs_fid_lookup(dentry->d_parent);
> }
> -void v9fs_fid_add(struct dentry *dentry, struct p9_fid *fid);
> +void v9fs_fid_add(struct dentry *dentry, struct p9_fid **fid);
> struct p9_fid *v9fs_writeback_fid(struct dentry *dentry);
> -void v9fs_open_fid_add(struct inode *inode, struct p9_fid *fid);
> +void v9fs_open_fid_add(struct inode *inode, struct p9_fid **fid);
> static inline struct p9_fid *clone_fid(struct p9_fid *fid)
> {
> return IS_ERR(fid) ? fid : p9_client_walk(fid, 0, NULL, 1);
> diff --git a/fs/9p/vfs_file.c b/fs/9p/vfs_file.c
> index 8276f3af35d7..aec43ba83799 100644
> --- a/fs/9p/vfs_file.c
> +++ b/fs/9p/vfs_file.c
> @@ -69,9 +69,10 @@ int v9fs_file_open(struct inode *inode, struct file *file)
> if ((file->f_flags & O_APPEND) &&
> (!v9fs_proto_dotu(v9ses) && !v9fs_proto_dotl(v9ses)))
> generic_file_llseek(file, 0, SEEK_END);
> +
> + file->private_data = fid;
> }
>
> - file->private_data = fid;
> mutex_lock(&v9inode->v_mutex);
> if ((v9ses->cache == CACHE_LOOSE || v9ses->cache == CACHE_FSCACHE) &&
> !v9inode->writeback_fid &&
> @@ -95,7 +96,7 @@ int v9fs_file_open(struct inode *inode, struct file *file)
> if (v9ses->cache == CACHE_LOOSE || v9ses->cache == CACHE_FSCACHE)
> fscache_use_cookie(v9fs_inode_cookie(v9inode),
> file->f_mode & FMODE_WRITE);
> - v9fs_open_fid_add(inode, fid);
> + v9fs_open_fid_add(inode, &fid);
> return 0;
> out_error:
> p9_fid_put(file->private_data);
> diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
> index 38186d1a1440..1b11a92208fd 100644
> --- a/fs/9p/vfs_inode.c
> +++ b/fs/9p/vfs_inode.c
> @@ -398,10 +398,8 @@ void v9fs_evict_inode(struct inode *inode)
>
> fscache_relinquish_cookie(v9fs_inode_cookie(v9inode), false);
> /* clunk the fid stashed in writeback_fid */
> - if (v9inode->writeback_fid) {
> - p9_fid_put(v9inode->writeback_fid);
> - v9inode->writeback_fid = NULL;
> - }
> + p9_fid_put(v9inode->writeback_fid);
> + v9inode->writeback_fid = NULL;
> }
>
> static int v9fs_test_inode(struct inode *inode, void *data)
> @@ -632,14 +630,12 @@ v9fs_create(struct v9fs_session_info *v9ses, struct inode *dir,
> if (IS_ERR(ofid)) {
> err = PTR_ERR(ofid);
> p9_debug(P9_DEBUG_VFS, "p9_client_walk failed %d\n", err);
> - p9_fid_put(dfid);
> - return ERR_PTR(err);
> + goto error;
> }
>
> err = p9_client_fcreate(ofid, name, perm, mode, extension);
> if (err < 0) {
> p9_debug(P9_DEBUG_VFS, "p9_client_fcreate failed %d\n", err);
> - p9_fid_put(dfid);
> goto error;
> }
>
> @@ -650,8 +646,6 @@ v9fs_create(struct v9fs_session_info *v9ses, struct inode *dir,
> err = PTR_ERR(fid);
> p9_debug(P9_DEBUG_VFS,
> "p9_client_walk failed %d\n", err);
> - fid = NULL;
> - p9_fid_put(dfid);
> goto error;
> }
> /*
> @@ -662,21 +656,17 @@ v9fs_create(struct v9fs_session_info *v9ses, struct inode *dir,
> err = PTR_ERR(inode);
> p9_debug(P9_DEBUG_VFS,
> "inode creation failed %d\n", err);
> - p9_fid_put(dfid);
> goto error;
> }
> - v9fs_fid_add(dentry, fid);
> + v9fs_fid_add(dentry, &fid);
> d_instantiate(dentry, inode);
> }
> p9_fid_put(dfid);
> return ofid;
> error:
> - if (ofid)
> - p9_fid_put(ofid);
> -
> - if (fid)
> - p9_fid_put(fid);
> -
> + p9_fid_put(dfid);
> + p9_fid_put(ofid);
> + p9_fid_put(fid);
> return ERR_PTR(err);
> }
>
> @@ -803,9 +793,9 @@ struct dentry *v9fs_vfs_lookup(struct inode *dir, struct dentry *dentry,
> res = d_splice_alias(inode, dentry);
> if (!IS_ERR(fid)) {
> if (!res)
> - v9fs_fid_add(dentry, fid);
> + v9fs_fid_add(dentry, &fid);
> else if (!IS_ERR(res))
> - v9fs_fid_add(res, fid);
> + v9fs_fid_add(res, &fid);
> else
> p9_fid_put(fid);
> }
> @@ -846,7 +836,6 @@ v9fs_vfs_atomic_open(struct inode *dir, struct dentry *dentry,
> v9fs_proto_dotu(v9ses)));
> if (IS_ERR(fid)) {
> err = PTR_ERR(fid);
> - fid = NULL;
> goto error;
> }
>
> @@ -881,7 +870,7 @@ v9fs_vfs_atomic_open(struct inode *dir, struct dentry *dentry,
> if (v9ses->cache == CACHE_LOOSE || v9ses->cache == CACHE_FSCACHE)
> fscache_use_cookie(v9fs_inode_cookie(v9inode),
> file->f_mode & FMODE_WRITE);
> - v9fs_open_fid_add(inode, fid);
> + v9fs_open_fid_add(inode, &fid);
>
> file->f_mode |= FMODE_CREATED;
> out:
> @@ -889,8 +878,7 @@ v9fs_vfs_atomic_open(struct inode *dir, struct dentry *dentry,
> return err;
>
> error:
> - if (fid)
> - p9_fid_put(fid);
> + p9_fid_put(fid);
> goto out;
> }
>
> @@ -938,9 +926,9 @@ v9fs_vfs_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
> struct inode *old_inode;
> struct inode *new_inode;
> struct v9fs_session_info *v9ses;
> - struct p9_fid *oldfid, *dfid;
> - struct p9_fid *olddirfid;
> - struct p9_fid *newdirfid;
> + struct p9_fid *oldfid = NULL, *dfid = NULL;
> + struct p9_fid *olddirfid = NULL;
> + struct p9_fid *newdirfid = NULL;
> struct p9_wstat wstat;
>
> if (flags)
> @@ -957,21 +945,22 @@ v9fs_vfs_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
>
> dfid = v9fs_parent_fid(old_dentry);
> olddirfid = clone_fid(dfid);
> - if (dfid && !IS_ERR(dfid))
> - p9_fid_put(dfid);
> + p9_fid_put(dfid);
> + dfid = NULL;
>
> if (IS_ERR(olddirfid)) {
> retval = PTR_ERR(olddirfid);
> - goto done;
> + goto error;
> }
>
> dfid = v9fs_parent_fid(new_dentry);
> newdirfid = clone_fid(dfid);
> p9_fid_put(dfid);
> + dfid = NULL;
>
> if (IS_ERR(newdirfid)) {
> retval = PTR_ERR(newdirfid);
> - goto clunk_olddir;
> + goto error;
> }
>
> down_write(&v9ses->rename_sem);
> @@ -982,7 +971,7 @@ v9fs_vfs_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
> retval = p9_client_rename(oldfid, newdirfid,
> new_dentry->d_name.name);
> if (retval != -EOPNOTSUPP)
> - goto clunk_newdir;
> + goto error_locked;
> }
> if (old_dentry->d_parent != new_dentry->d_parent) {
> /*
> @@ -991,14 +980,14 @@ v9fs_vfs_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
>
> p9_debug(P9_DEBUG_ERROR, "old dir and new dir are different\n");
> retval = -EXDEV;
> - goto clunk_newdir;
> + goto error_locked;
> }
> v9fs_blank_wstat(&wstat);
> wstat.muid = v9ses->uname;
> wstat.name = new_dentry->d_name.name;
> retval = p9_client_wstat(oldfid, &wstat);
>
> -clunk_newdir:
> +error_locked:
> if (!retval) {
> if (new_inode) {
> if (S_ISDIR(new_inode->i_mode))
> @@ -1019,12 +1008,10 @@ v9fs_vfs_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
> d_move(old_dentry, new_dentry);
> }
> up_write(&v9ses->rename_sem);
> +
> +error:
> p9_fid_put(newdirfid);
> -
> -clunk_olddir:
> p9_fid_put(olddirfid);
> -
> -done:
> p9_fid_put(oldfid);
> return retval;
> }
> diff --git a/fs/9p/vfs_inode_dotl.c b/fs/9p/vfs_inode_dotl.c
> index 09b124fe349c..5cfa4b4f070f 100644
> --- a/fs/9p/vfs_inode_dotl.c
> +++ b/fs/9p/vfs_inode_dotl.c
> @@ -238,7 +238,7 @@ v9fs_vfs_atomic_open_dotl(struct inode *dir, struct dentry *dentry,
> struct inode *inode;
> struct p9_fid *fid = NULL;
> struct v9fs_inode *v9inode;
> - struct p9_fid *dfid, *ofid, *inode_fid;
> + struct p9_fid *dfid = NULL, *ofid = NULL, *inode_fid = NULL;
> struct v9fs_session_info *v9ses;
> struct posix_acl *pacl = NULL, *dacl = NULL;
> struct dentry *res = NULL;
> @@ -274,7 +274,6 @@ v9fs_vfs_atomic_open_dotl(struct inode *dir, struct dentry *dentry,
> if (IS_ERR(ofid)) {
> err = PTR_ERR(ofid);
> p9_debug(P9_DEBUG_VFS, "p9_client_walk failed %d\n", err);
> - p9_fid_put(dfid);
> goto out;
> }
>
> @@ -286,38 +285,34 @@ v9fs_vfs_atomic_open_dotl(struct inode *dir, struct dentry *dentry,
> if (err) {
> p9_debug(P9_DEBUG_VFS, "Failed to get acl values in creat %d\n",
> err);
> - p9_fid_put(dfid);
> - goto error;
> + goto out;
> }
> err = p9_client_create_dotl(ofid, name, v9fs_open_to_dotl_flags(flags),
> mode, gid, &qid);
> if (err < 0) {
> p9_debug(P9_DEBUG_VFS, "p9_client_open_dotl failed in creat %d\n",
> err);
> - p9_fid_put(dfid);
> - goto error;
> + goto out;
> }
> v9fs_invalidate_inode_attr(dir);
>
> /* instantiate inode and assign the unopened fid to the dentry */
> fid = p9_client_walk(dfid, 1, &name, 1);
> - p9_fid_put(dfid);
> if (IS_ERR(fid)) {
> err = PTR_ERR(fid);
> p9_debug(P9_DEBUG_VFS, "p9_client_walk failed %d\n", err);
> - fid = NULL;
> - goto error;
> + goto out;
> }
> inode = v9fs_get_new_inode_from_fid(v9ses, fid, dir->i_sb);
> if (IS_ERR(inode)) {
> err = PTR_ERR(inode);
> p9_debug(P9_DEBUG_VFS, "inode creation failed %d\n", err);
> - goto error;
> + goto out;
> }
> /* Now set the ACL based on the default value */
> v9fs_set_create_acl(inode, fid, dacl, pacl);
>
> - v9fs_fid_add(dentry, fid);
> + v9fs_fid_add(dentry, &fid);
> d_instantiate(dentry, inode);
>
> v9inode = V9FS_I(inode);
> @@ -336,7 +331,7 @@ v9fs_vfs_atomic_open_dotl(struct inode *dir, struct dentry *dentry,
> if (IS_ERR(inode_fid)) {
> err = PTR_ERR(inode_fid);
> mutex_unlock(&v9inode->v_mutex);
> - goto err_clunk_old_fid;
> + goto out;
> }
> v9inode->writeback_fid = (void *) inode_fid;
> }
> @@ -344,25 +339,20 @@ v9fs_vfs_atomic_open_dotl(struct inode *dir, struct dentry *dentry,
> /* Since we are opening a file, assign the open fid to the file */
> err = finish_open(file, dentry, generic_file_open);
> if (err)
> - goto err_clunk_old_fid;
> + goto out;
> file->private_data = ofid;
> if (v9ses->cache == CACHE_LOOSE || v9ses->cache == CACHE_FSCACHE)
> fscache_use_cookie(v9fs_inode_cookie(v9inode),
> file->f_mode & FMODE_WRITE);
> - v9fs_open_fid_add(inode, ofid);
> + v9fs_open_fid_add(inode, &ofid);
> file->f_mode |= FMODE_CREATED;
> out:
> + p9_fid_put(dfid);
> + p9_fid_put(ofid);
> + p9_fid_put(fid);
> v9fs_put_acl(dacl, pacl);
> dput(res);
> return err;
> -
> -error:
> - if (fid)
> - p9_fid_put(fid);
> -err_clunk_old_fid:
> - if (ofid)
> - p9_fid_put(ofid);
> - goto out;
> }
>
> /**
> @@ -400,7 +390,6 @@ static int v9fs_vfs_mkdir_dotl(struct user_namespace *mnt_userns,
> if (IS_ERR(dfid)) {
> err = PTR_ERR(dfid);
> p9_debug(P9_DEBUG_VFS, "fid lookup failed %d\n", err);
> - dfid = NULL;
> goto error;
> }
>
> @@ -422,7 +411,6 @@ static int v9fs_vfs_mkdir_dotl(struct user_namespace *mnt_userns,
> err = PTR_ERR(fid);
> p9_debug(P9_DEBUG_VFS, "p9_client_walk failed %d\n",
> err);
> - fid = NULL;
> goto error;
> }
>
> @@ -435,10 +423,9 @@ static int v9fs_vfs_mkdir_dotl(struct user_namespace *mnt_userns,
> err);
> goto error;
> }
> - v9fs_fid_add(dentry, fid);
> + v9fs_fid_add(dentry, &fid);
> v9fs_set_create_acl(inode, fid, dacl, pacl);
> d_instantiate(dentry, inode);
> - fid = NULL;
> err = 0;
> } else {
> /*
> @@ -457,8 +444,7 @@ static int v9fs_vfs_mkdir_dotl(struct user_namespace *mnt_userns,
> inc_nlink(dir);
> v9fs_invalidate_inode_attr(dir);
> error:
> - if (fid)
> - p9_fid_put(fid);
> + p9_fid_put(fid);
> v9fs_put_acl(dacl, pacl);
> p9_fid_put(dfid);
> return err;
> @@ -743,7 +729,6 @@ v9fs_vfs_symlink_dotl(struct user_namespace *mnt_userns, struct inode *dir,
> err = PTR_ERR(fid);
> p9_debug(P9_DEBUG_VFS, "p9_client_walk failed %d\n",
> err);
> - fid = NULL;
> goto error;
> }
>
> @@ -755,9 +740,8 @@ v9fs_vfs_symlink_dotl(struct user_namespace *mnt_userns, struct inode *dir,
> err);
> goto error;
> }
> - v9fs_fid_add(dentry, fid);
> + v9fs_fid_add(dentry, &fid);
> d_instantiate(dentry, inode);
> - fid = NULL;
> err = 0;
> } else {
> /* Not in cached mode. No need to populate inode with stat */
> @@ -770,9 +754,7 @@ v9fs_vfs_symlink_dotl(struct user_namespace *mnt_userns, struct inode *dir,
> }
>
> error:
> - if (fid)
> - p9_fid_put(fid);
> -
> + p9_fid_put(fid);
> p9_fid_put(dfid);
> return err;
> }
> @@ -866,7 +848,6 @@ v9fs_vfs_mknod_dotl(struct user_namespace *mnt_userns, struct inode *dir,
> if (IS_ERR(dfid)) {
> err = PTR_ERR(dfid);
> p9_debug(P9_DEBUG_VFS, "fid lookup failed %d\n", err);
> - dfid = NULL;
> goto error;
> }
>
> @@ -891,7 +872,6 @@ v9fs_vfs_mknod_dotl(struct user_namespace *mnt_userns, struct inode *dir,
> err = PTR_ERR(fid);
> p9_debug(P9_DEBUG_VFS, "p9_client_walk failed %d\n",
> err);
> - fid = NULL;
> goto error;
> }
>
> @@ -905,9 +885,8 @@ v9fs_vfs_mknod_dotl(struct user_namespace *mnt_userns, struct inode *dir,
> goto error;
> }
> v9fs_set_create_acl(inode, fid, dacl, pacl);
> - v9fs_fid_add(dentry, fid);
> + v9fs_fid_add(dentry, &fid);
> d_instantiate(dentry, inode);
> - fid = NULL;
> err = 0;
> } else {
> /*
> @@ -923,8 +902,7 @@ v9fs_vfs_mknod_dotl(struct user_namespace *mnt_userns, struct inode *dir,
> d_instantiate(dentry, inode);
> }
> error:
> - if (fid)
> - p9_fid_put(fid);
> + p9_fid_put(fid);
> v9fs_put_acl(dacl, pacl);
> p9_fid_put(dfid);
>
> diff --git a/fs/9p/vfs_super.c b/fs/9p/vfs_super.c
> index bf350fad9500..2d9ee073d12c 100644
> --- a/fs/9p/vfs_super.c
> +++ b/fs/9p/vfs_super.c
> @@ -184,7 +184,7 @@ static struct dentry *v9fs_mount(struct file_system_type *fs_type, int flags,
> retval = v9fs_get_acl(inode, fid);
> if (retval)
> goto release_sb;
> - v9fs_fid_add(root, fid);
> + v9fs_fid_add(root, &fid);
>
> p9_debug(P9_DEBUG_VFS, " simple set mount, return 0\n");
> return dget(sb->s_root);
> --
> 2.35.1
>

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