From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7240E2F872 for ; Thu, 2 Oct 2025 17:02:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759424543; cv=none; b=S7DGRTBWHEpL7JCo1fp3yXReauM34+wBG036qlxE1qAeohVX0DDsNeQO4/tshLkXRN5RcAtIpvooobbEk3GK66hMcnZOWvDUjKvmSAQ1VLwpXZzQhd9VwvGe/WVMwBot/3t3FlC49a0byIrXCxh2k2xtk+zpvaUYe3s3iL5R+aM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759424543; c=relaxed/simple; bh=W7Mhfv1IaHuNCglFjLSlDnErWGWub++cX4XVVQk8XmU=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=ukUyK8ZHvEW+BTaV0yhNxlmBFyBLU3AgBrLv7Ao6Os2pPfpnq/MTYE75C672LlWT4GXgqNOnTGKF2USh6HL4UlfIi0Q1AxhyJ83M3qOmcy6T9HpLEP7D4VRBzHUGRu0eUY3JKA5Wntn3duuZY9H455AWwvRYHTGxQvxcnhZ1KtI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=QYwTPx1b; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="QYwTPx1b" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 776F1C4CEF4; Thu, 2 Oct 2025 17:02:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1759424542; bh=W7Mhfv1IaHuNCglFjLSlDnErWGWub++cX4XVVQk8XmU=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=QYwTPx1bdptiFf5AgxGPXy7SCP7BnOCltZL1Vd0lEe4f6ip4zFjF1kr87lD/U0i5o HJ2jnQg3XBhUNUXKlWJfbxznXpumyQf5QUXa6flW0Nhzbx3nt4vSzMUfGixZ5n+xJt N1xaNA9MAXlMqFzv0RocSme8lp/BYkc6oJRlx676lKm4YIB36jyRjipGp2e4FFuSoZ 1SKcjvBTpVx4VDM5/BcA3zndDzt2ya0mNGivhTKDuu+/ZWm86Bx90twNBaDrW0UKbH D1CnAEAtw6iFdnXO8GJFzk44Gx0Ae99eOzH2bgnV8EHFlzSqQEQy6+bJQ16krv+XoM L+h2Uk+gXCnDw== Message-ID: Subject: Re: [PATCH 04/11] VFS/nfsd/cachefiles/ovl: introduce start_removing() and end_removing() From: Jeff Layton To: NeilBrown , Alexander Viro , Christian Brauner , Amir Goldstein Cc: Jan Kara , linux-fsdevel@vger.kernel.org Date: Thu, 02 Oct 2025 13:02:20 -0400 In-Reply-To: <20250926025015.1747294-5-neilb@ownmail.net> References: <20250926025015.1747294-1-neilb@ownmail.net> <20250926025015.1747294-5-neilb@ownmail.net> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV T2h6v8i8YqsATFPwO4nuiTmL6I40ZofxVd+9wdRI4Db8yUNA4ZSP2nqLcLtFjClYRBoJvRWvsv4lm 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2tAMJUvFTdDbfe3zKlPDTuVsyNsALBGclPLagJ5ZTP+Vp2irAN9uwBuacBOTtmOdz4ZN2tdvNgozz uxp4CHBDVzAslUi2idy+xpsp47DWPxYFIRP3M8QG/aNW052LaPc0cedYxp8+9eiVUNpxF4SiU4i9J DfX/sn9XcfoVZIxMpCRE750zvJvcCUz9HojsrMQ1NFc7MFT1z3MOW2/RlzPcog7xvR5ENPH19ojRD CHqumUHRry+RF0lH00clzX/W8OrQJZtoBPXv9ahka/Vp7kEulcBJr1cH5Wz/WprhsIM7U9pse1f1g Yy9YbXtWctUz8uvDR7shsQxAhX3qO7DilMtuGo1v97I/Kx4gXQ52syh/w6EBny71CZrOgD6kJwPVV AaM1LRC28muq91WCFhs/nzHozpbzcheyGtMUI2Ao4K6mnY+3zIuXPygZMFr9KXE6fF7HzKxKuZMJO aEZCiDOq0anx6FmOzs5E6Jqdpo/mtI8beK+BE7Va6ni7YrQlnT0i3vaTVMTiCThbqsB20VrbMjlhp f8lfK1XVNbRq/R7GZ9zHESlsa35ha60yd/j3pu5hT2xyy8krV8vGhHvnJ1XRMJBAB/UYb6FyC7S+m QZIQXVeAA+smfTT0tDrisj1U5x6ZB9b3nBg65kc= Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.56.2 (3.56.2-2.fc42) Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Fri, 2025-09-26 at 12:49 +1000, NeilBrown wrote: > From: NeilBrown >=20 > start_removing() is similar to start_creating() but will only return a > positive dentry with the expectation that it will be removed. This is > used by nfsd, cachefiles, and overlayfs. They are changed to also use > end_removing() to terminate the action begun by start_removing(). This > is a simple alias for end_dirop(). >=20 > Apart from changes to the error paths, as we no longer need to unlock on > a lookup error, an effect on callers is that they don't need to test if > the found dentry is positive or negative - they can be sure it is > positive. >=20 > Signed-off-by: NeilBrown > --- > fs/cachefiles/namei.c | 25 ++++++++++--------------- > fs/namei.c | 27 +++++++++++++++++++++++++++ > fs/nfsd/nfs4recover.c | 18 +++++------------- > fs/nfsd/vfs.c | 26 ++++++++++---------------- > fs/overlayfs/dir.c | 15 +++++++-------- > fs/overlayfs/overlayfs.h | 8 ++++++++ > include/linux/namei.h | 17 +++++++++++++++++ > 7 files changed, 84 insertions(+), 52 deletions(-) >=20 > diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c > index 965b22b2f58d..3064d439807b 100644 > --- a/fs/cachefiles/namei.c > +++ b/fs/cachefiles/namei.c > @@ -260,6 +260,7 @@ static int cachefiles_unlink(struct cachefiles_cache = *cache, > * - File backed objects are unlinked > * - Directory backed objects are stuffed into the graveyard for userspa= ce to > * delete > + * On entry dir must be locked. It will be unlocked on exit. > */ > int cachefiles_bury_object(struct cachefiles_cache *cache, > struct cachefiles_object *object, > @@ -275,7 +276,8 @@ int cachefiles_bury_object(struct cachefiles_cache *c= ache, > _enter(",'%pd','%pd'", dir, rep); > =20 > if (rep->d_parent !=3D dir) { > - inode_unlock(d_inode(dir)); > + dget(rep); > + end_removing(rep); > _leave(" =3D -ESTALE"); > return -ESTALE; > } > @@ -286,16 +288,16 @@ int cachefiles_bury_object(struct cachefiles_cache = *cache, > * by a file struct. > */ > ret =3D cachefiles_unlink(cache, object, dir, rep, why); > - dput(rep); > + end_removing(rep); > =20 > - inode_unlock(d_inode(dir)); > _leave(" =3D %d", ret); > return ret; > } > =20 > /* directories have to be moved to the graveyard */ > _debug("move stale object to graveyard"); > - inode_unlock(d_inode(dir)); > + dget(rep); > + end_removing(rep); > =20 > try_again: > /* first step is to make up a grave dentry in the graveyard */ > @@ -745,26 +747,20 @@ static struct dentry *cachefiles_lookup_for_cull(st= ruct cachefiles_cache *cache, > struct dentry *victim; > int ret =3D -ENOENT; > =20 > - inode_lock_nested(d_inode(dir), I_MUTEX_PARENT); > + victim =3D start_removing(&nop_mnt_idmap, dir, &QSTR(filename)); > =20 > - victim =3D lookup_one(&nop_mnt_idmap, &QSTR(filename), dir); > if (IS_ERR(victim)) > goto lookup_error; > - if (d_is_negative(victim)) > - goto lookup_put; > if (d_inode(victim)->i_flags & S_KERNEL_FILE) > goto lookup_busy; > return victim; > =20 > lookup_busy: > ret =3D -EBUSY; > -lookup_put: > - inode_unlock(d_inode(dir)); > - dput(victim); > + end_removing(victim); > return ERR_PTR(ret); > =20 > lookup_error: > - inode_unlock(d_inode(dir)); > ret =3D PTR_ERR(victim); > if (ret =3D=3D -ENOENT) > return ERR_PTR(-ESTALE); /* Probably got retired by the netfs */ > @@ -812,18 +808,17 @@ int cachefiles_cull(struct cachefiles_cache *cache,= struct dentry *dir, > =20 > ret =3D cachefiles_bury_object(cache, NULL, dir, victim, > FSCACHE_OBJECT_WAS_CULLED); > + dput(victim); > if (ret < 0) > goto error; > =20 > fscache_count_culled(); > - dput(victim); > _leave(" =3D 0"); > return 0; > =20 > error_unlock: > - inode_unlock(d_inode(dir)); > + end_removing(victim); > error: > - dput(victim); > if (ret =3D=3D -ENOENT) > return -ESTALE; /* Probably got retired by the netfs */ > =20 > diff --git a/fs/namei.c b/fs/namei.c > index 064cb44a3a46..0d9e98961758 100644 > --- a/fs/namei.c > +++ b/fs/namei.c > @@ -3269,6 +3269,33 @@ struct dentry *start_creating(struct mnt_idmap *id= map, struct dentry *parent, > } > EXPORT_SYMBOL(start_creating); > =20 > +/** > + * start_removing - prepare to remove a given name with permission check= ing > + * @idmap - idmap of the mount > + * @parent - directory in which to find the name > + * @name - the name to be removed > + * > + * Locks are taken and a lookup in performed prior to removing > + * an object from a directory. Permission checking (MAY_EXEC) is perfor= med > + * against @idmap. > + * > + * If the name doesn't exist, an error is returned. > + * > + * end_removing() should be called when removal is complete, or aborted. > + * > + * Returns: a positive dentry, or an error. > + */ > +struct dentry *start_removing(struct mnt_idmap *idmap, struct dentry *pa= rent, > + struct qstr *name) > +{ > + int err =3D lookup_one_common(idmap, name, parent); > + > + if (err) > + return ERR_PTR(err); > + return start_dirop(parent, name, 0); > +} > +EXPORT_SYMBOL(start_removing); > + > #ifdef CONFIG_UNIX98_PTYS > int path_pts(struct path *path) > { > diff --git a/fs/nfsd/nfs4recover.c b/fs/nfsd/nfs4recover.c > index 93b2a3e764db..0f33e13a9da2 100644 > --- a/fs/nfsd/nfs4recover.c > +++ b/fs/nfsd/nfs4recover.c > @@ -345,20 +345,12 @@ nfsd4_unlink_clid_dir(char *name, struct nfsd_net *= nn) > dprintk("NFSD: nfsd4_unlink_clid_dir. name %s\n", name); > =20 > dir =3D nn->rec_file->f_path.dentry; > - inode_lock_nested(d_inode(dir), I_MUTEX_PARENT); > - dentry =3D lookup_one(&nop_mnt_idmap, &QSTR(name), dir); > - if (IS_ERR(dentry)) { > - status =3D PTR_ERR(dentry); > - goto out_unlock; > - } > - status =3D -ENOENT; > - if (d_really_is_negative(dentry)) > - goto out; > + dentry =3D start_removing(&nop_mnt_idmap, dir, &QSTR(name)); > + if (IS_ERR(dentry)) > + return PTR_ERR(dentry); > + > status =3D vfs_rmdir(&nop_mnt_idmap, d_inode(dir), dentry); > -out: > - dput(dentry); > -out_unlock: > - inode_unlock(d_inode(dir)); > + end_removing(dentry); > return status; > } > =20 > diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c > index 90c830c59c60..d5b4550fd8f6 100644 > --- a/fs/nfsd/vfs.c > +++ b/fs/nfsd/vfs.c > @@ -2021,7 +2021,7 @@ nfsd_unlink(struct svc_rqst *rqstp, struct svc_fh *= fhp, int type, > { > struct dentry *dentry, *rdentry; > struct inode *dirp; > - struct inode *rinode; > + struct inode *rinode =3D NULL; > __be32 err; > int host_err; > =20 > @@ -2040,24 +2040,21 @@ nfsd_unlink(struct svc_rqst *rqstp, struct svc_fh= *fhp, int type, > =20 > dentry =3D fhp->fh_dentry; > dirp =3D d_inode(dentry); > - inode_lock_nested(dirp, I_MUTEX_PARENT); > =20 > - rdentry =3D lookup_one(&nop_mnt_idmap, &QSTR_LEN(fname, flen), dentry); > + rdentry =3D start_removing(&nop_mnt_idmap, dentry, &QSTR_LEN(fname, fle= n)); > + > host_err =3D PTR_ERR(rdentry); > if (IS_ERR(rdentry)) > - goto out_unlock; > + goto out_drop_write; > =20 > - if (d_really_is_negative(rdentry)) { > - dput(rdentry); > - host_err =3D -ENOENT; > - goto out_unlock; > - } > - rinode =3D d_inode(rdentry); > err =3D fh_fill_pre_attrs(fhp); > if (err !=3D nfs_ok) > goto out_unlock; > =20 > + rinode =3D d_inode(rdentry); > + /* Prevent truncation until after locks dropped */ > ihold(rinode); > + > if (!type) > type =3D d_inode(rdentry)->i_mode & S_IFMT; > =20 > @@ -2079,10 +2076,10 @@ nfsd_unlink(struct svc_rqst *rqstp, struct svc_fh= *fhp, int type, > } > fh_fill_post_attrs(fhp); > =20 > - inode_unlock(dirp); > - if (!host_err) > +out_unlock: > + end_removing(rdentry); > + if (!err && !host_err) > host_err =3D commit_metadata(fhp); > - dput(rdentry); > iput(rinode); /* truncate the inode here */ > =20 > out_drop_write: > @@ -2100,9 +2097,6 @@ nfsd_unlink(struct svc_rqst *rqstp, struct svc_fh *= fhp, int type, > } > out: > return err !=3D nfs_ok ? err : nfserrno(host_err); > -out_unlock: > - inode_unlock(dirp); > - goto out_drop_write; > } >=20 >=20 I like how the new helper simplifies this code. > =20 > /* > diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c > index 0ae79efbfce7..c4057b4a050d 100644 > --- a/fs/overlayfs/dir.c > +++ b/fs/overlayfs/dir.c > @@ -841,17 +841,17 @@ static int ovl_remove_upper(struct dentry *dentry, = bool is_dir, > goto out; > } > =20 > - inode_lock_nested(dir, I_MUTEX_PARENT); > - upper =3D ovl_lookup_upper(ofs, dentry->d_name.name, upperdir, > - dentry->d_name.len); > + upper =3D ovl_start_removing_upper(ofs, upperdir, > + &QSTR_LEN(dentry->d_name.name, > + dentry->d_name.len)); > err =3D PTR_ERR(upper); > if (IS_ERR(upper)) > - goto out_unlock; > + goto out_dput; > =20 > err =3D -ESTALE; > if ((opaquedir && upper !=3D opaquedir) || > (!opaquedir && !ovl_matches_upper(dentry, upper))) > - goto out_dput_upper; > + goto out_unlock; > =20 > if (is_dir) > err =3D ovl_do_rmdir(ofs, dir, upper); > @@ -867,10 +867,9 @@ static int ovl_remove_upper(struct dentry *dentry, b= ool is_dir, > */ > if (!err) > d_drop(dentry); > -out_dput_upper: > - dput(upper); > out_unlock: > - inode_unlock(dir); > + end_removing(upper); > +out_dput: > dput(opaquedir); > out: > return err; > diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h > index c24c2da953bd..915af58459b7 100644 > --- a/fs/overlayfs/overlayfs.h > +++ b/fs/overlayfs/overlayfs.h > @@ -423,6 +423,14 @@ static inline struct dentry *ovl_start_creating_uppe= r(struct ovl_fs *ofs, > parent, name); > } > =20 > +static inline struct dentry *ovl_start_removing_upper(struct ovl_fs *ofs= , > + struct dentry *parent, > + struct qstr *name) > +{ > + return start_removing(ovl_upper_mnt_idmap(ofs), > + parent, name); > +} > + > static inline bool ovl_open_flags_need_copy_up(int flags) > { > if (!flags) > diff --git a/include/linux/namei.h b/include/linux/namei.h > index 4cbe930054a1..63941fdbc23d 100644 > --- a/include/linux/namei.h > +++ b/include/linux/namei.h > @@ -90,6 +90,8 @@ struct dentry *lookup_one_positive_killable(struct mnt_= idmap *idmap, > =20 > struct dentry *start_creating(struct mnt_idmap *idmap, struct dentry *pa= rent, > struct qstr *name); > +struct dentry *start_removing(struct mnt_idmap *idmap, struct dentry *pa= rent, > + struct qstr *name); > =20 > /* end_creating - finish action started with start_creating > * @child - dentry returned by start_creating() > @@ -106,6 +108,21 @@ static inline void end_creating(struct dentry *child= , struct dentry *parent) > end_dirop_mkdir(child, parent); > } > =20 > +/* end_removing - finish action started with start_removing > + * @child - dentry returned by start_removing() > + * @parent - dentry given to start_removing() > + * > + * Unlock and release the child. > + * > + * This is identical to end_dirop(). It can be passed the result of > + * start_removing() whether that was successful or not, but it not neede= d > + * if start_removing() failed. > + */ > +static inline void end_removing(struct dentry *child) > +{ > + end_dirop(child); > +} > + > extern int follow_down_one(struct path *); > extern int follow_down(struct path *path, unsigned int flags); > extern int follow_up(struct path *); Reviewed-by: Jeff Layton