From nobody Sun Feb 8 01:51:48 2026 Received: from mail-m49197.qiye.163.com (mail-m49197.qiye.163.com [45.254.49.197]) (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 BF89F1E32A2; Mon, 19 Jan 2026 08:38:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.254.49.197 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768811892; cv=none; b=bAX4s3yduE7N1AxooSkOD5Lgny7c/+ygVPvX+f2KMnWYUqJ5fIVowa6wRBPbK+XczTBGVTDiTou9ySjeyzdpqjKvo8Kwe+gVHar0r6q8WQ1yYyXpL8oqdq7zblRd4IlZNOMvozpHBG00HxSmhlb+ZRUWYxaByRHvJ79k/5QOyJA= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768811892; c=relaxed/simple; bh=2cSfdHeedI/T42Za45EvNfauDrNmA1WD2QccVqafIMc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=WwzgXSXJ4+sC9J/BsvpDgatk1HaauKRvzv5W2hPoDEi1OgKWWLhygFADbVbztwSmCoRTl5XG8Z8CKFRnTFt1pL7pie4FeLsHxTViKcOoIOpfKMth8AEfJyxow9g+Qfg6w8djWkNXAR8rQ0kx5pN3fSz+88m9FQLzVjtI32byk8o= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=ustc.edu; spf=pass smtp.mailfrom=ustc.edu; arc=none smtp.client-ip=45.254.49.197 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=ustc.edu Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ustc.edu Received: from localhost (unknown [14.22.11.162]) by smtp.qiye.163.com (Hmail) with ESMTP id 3122c8158; Mon, 19 Jan 2026 16:38:06 +0800 (GMT+08:00) From: Chunsheng Luo To: miklos@szeredi.hu Cc: amir73il@gmail.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Chunsheng Luo Subject: [PATCH v3 1/2] fuse: add ioctl to cleanup all backing files Date: Mon, 19 Jan 2026 16:37:48 +0800 Message-ID: <20260119083750.2055-2-luochunsheng@ustc.edu> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260119083750.2055-1-luochunsheng@ustc.edu> References: <20260119083750.2055-1-luochunsheng@ustc.edu> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-HM-Tid: 0a9bd56777bc03a2kunm42914fd4316265 X-HM-MType: 10 X-HM-Spam-Status: e1kfGhgUHx5ZQUtXWQgPGg8OCBgUHx5ZQUlOS1dZFg8aDwILHllBWSg2Ly tZV1koWUFITzdXWS1ZQUlXWQ8JGhUIEh9ZQVlCQ0wZVkJCShoYHh9OQhhLGVYeHw5VEwETFhoSFy QUDg9ZV1kYEgtZQVlKT1VJSVVKSlVKTUlZV1kWGg8SFR0UWUFZS1VLVUtVS1kG Content-Type: text/plain; charset="utf-8" To simplify crash recovery and reduce performance impact, backing_ids are not persisted across daemon restarts. After crash recovery, this may lead to resource leaks if backing file resources are not properly cleaned up. Add FUSE_DEV_IOC_BACKING_CLOSE_ALL ioctl to release all backing_ids and put backing files. When the FUSE daemon restarts, it can use this ioctl to cleanup all backing file resources. Reviewed-by: Amir Goldstein Signed-off-by: Chunsheng Luo --- fs/fuse/backing.c | 76 +++++++++++++++++++++++++++++++++++---- fs/fuse/dev.c | 16 +++++++++ fs/fuse/fuse_i.h | 5 +-- fs/fuse/inode.c | 11 +++--- include/uapi/linux/fuse.h | 1 + 5 files changed, 94 insertions(+), 15 deletions(-) diff --git a/fs/fuse/backing.c b/fs/fuse/backing.c index 4afda419dd14..31ad6a60a085 100644 --- a/fs/fuse/backing.c +++ b/fs/fuse/backing.c @@ -32,19 +32,29 @@ void fuse_backing_put(struct fuse_backing *fb) fuse_backing_free(fb); } =20 -void fuse_backing_files_init(struct fuse_conn *fc) +int fuse_backing_files_init(struct fuse_conn *fc) { - idr_init(&fc->backing_files_map); + struct idr *idr; + + idr =3D kzalloc(sizeof(*idr), GFP_KERNEL); + if (!idr) + return -ENOMEM; + idr_init(idr); + rcu_assign_pointer(fc->backing_files_map, idr); + return 0; } =20 static int fuse_backing_id_alloc(struct fuse_conn *fc, struct fuse_backing= *fb) { + struct idr *idr; int id; =20 idr_preload(GFP_KERNEL); spin_lock(&fc->lock); + idr =3D rcu_dereference_protected(fc->backing_files_map, + lockdep_is_held(&fc->lock)); /* FIXME: xarray might be space inefficient */ - id =3D idr_alloc_cyclic(&fc->backing_files_map, fb, 1, 0, GFP_ATOMIC); + id =3D idr_alloc_cyclic(idr, fb, 1, 0, GFP_ATOMIC); spin_unlock(&fc->lock); idr_preload_end(); =20 @@ -55,10 +65,13 @@ static int fuse_backing_id_alloc(struct fuse_conn *fc, = struct fuse_backing *fb) static struct fuse_backing *fuse_backing_id_remove(struct fuse_conn *fc, int id) { + struct idr *idr; struct fuse_backing *fb; =20 spin_lock(&fc->lock); - fb =3D idr_remove(&fc->backing_files_map, id); + idr =3D rcu_dereference_protected(fc->backing_files_map, + lockdep_is_held(&fc->lock)); + fb =3D idr_remove(idr, id); spin_unlock(&fc->lock); =20 return fb; @@ -75,8 +88,13 @@ static int fuse_backing_id_free(int id, void *p, void *d= ata) =20 void fuse_backing_files_free(struct fuse_conn *fc) { - idr_for_each(&fc->backing_files_map, fuse_backing_id_free, NULL); - idr_destroy(&fc->backing_files_map); + struct idr *idr =3D rcu_dereference_protected(fc->backing_files_map, 1); + + if (idr) { + idr_for_each(idr, fuse_backing_id_free, NULL); + idr_destroy(idr); + kfree(idr); + } } =20 int fuse_backing_open(struct fuse_conn *fc, struct fuse_backing_map *map) @@ -166,12 +184,56 @@ int fuse_backing_close(struct fuse_conn *fc, int back= ing_id) return err; } =20 +int fuse_backing_close_all(struct fuse_conn *fc) +{ + struct idr *old_idr, *new_idr; + struct fuse_backing *fb; + int id; + + if (!fc->passthrough || !capable(CAP_SYS_ADMIN)) + return -EPERM; + + new_idr =3D kzalloc(sizeof(*new_idr), GFP_KERNEL); + if (!new_idr) + return -ENOMEM; + + idr_init(new_idr); + + /* + * Atomically exchange the old IDR with a new empty one under lock. + * This avoids long lock hold times and races with concurrent + * open/close operations. + */ + spin_lock(&fc->lock); + old_idr =3D rcu_replace_pointer(fc->backing_files_map, new_idr, + lockdep_is_held(&fc->lock)); + spin_unlock(&fc->lock); + + /* + * Ensure all concurrent RCU readers complete before releasing backing + * files, so any in-flight lookups can safely take references. + */ + synchronize_rcu(); + + if (old_idr) { + idr_for_each_entry(old_idr, fb, id) + fuse_backing_put(fb); + + idr_destroy(old_idr); + kfree(old_idr); + } + + return 0; +} + struct fuse_backing *fuse_backing_lookup(struct fuse_conn *fc, int backing= _id) { + struct idr *idr; struct fuse_backing *fb; =20 rcu_read_lock(); - fb =3D idr_find(&fc->backing_files_map, backing_id); + idr =3D rcu_dereference(fc->backing_files_map); + fb =3D idr ? idr_find(idr, backing_id) : NULL; fb =3D fuse_backing_get(fb); rcu_read_unlock(); =20 diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c index 6d59cbc877c6..f05d55302598 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -2654,6 +2654,19 @@ static long fuse_dev_ioctl_backing_close(struct file= *file, __u32 __user *argp) return fuse_backing_close(fud->fc, backing_id); } =20 +static long fuse_dev_ioctl_backing_close_all(struct file *file) +{ + struct fuse_dev *fud =3D fuse_get_dev(file); + + if (IS_ERR(fud)) + return PTR_ERR(fud); + + if (!IS_ENABLED(CONFIG_FUSE_PASSTHROUGH)) + return -EOPNOTSUPP; + + return fuse_backing_close_all(fud->fc); +} + static long fuse_dev_ioctl_sync_init(struct file *file) { int err =3D -EINVAL; @@ -2682,6 +2695,9 @@ static long fuse_dev_ioctl(struct file *file, unsigne= d int cmd, case FUSE_DEV_IOC_BACKING_CLOSE: return fuse_dev_ioctl_backing_close(file, argp); =20 + case FUSE_DEV_IOC_BACKING_CLOSE_ALL: + return fuse_dev_ioctl_backing_close_all(file); + case FUSE_DEV_IOC_SYNC_INIT: return fuse_dev_ioctl_sync_init(file); =20 diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h index 7f16049387d1..f45c5042e31a 100644 --- a/fs/fuse/fuse_i.h +++ b/fs/fuse/fuse_i.h @@ -979,7 +979,7 @@ struct fuse_conn { =20 #ifdef CONFIG_FUSE_PASSTHROUGH /** IDR for backing files ids */ - struct idr backing_files_map; + struct idr __rcu *backing_files_map; #endif =20 #ifdef CONFIG_FUSE_IO_URING @@ -1569,10 +1569,11 @@ static inline struct fuse_backing *fuse_backing_loo= kup(struct fuse_conn *fc, } #endif =20 -void fuse_backing_files_init(struct fuse_conn *fc); +int fuse_backing_files_init(struct fuse_conn *fc); void fuse_backing_files_free(struct fuse_conn *fc); int fuse_backing_open(struct fuse_conn *fc, struct fuse_backing_map *map); int fuse_backing_close(struct fuse_conn *fc, int backing_id); +int fuse_backing_close_all(struct fuse_conn *fc); =20 /* passthrough.c */ static inline struct fuse_backing *fuse_inode_backing(struct fuse_inode *f= i) diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c index 819e50d66622..b63a067d50f8 100644 --- a/fs/fuse/inode.c +++ b/fs/fuse/inode.c @@ -1001,9 +1001,6 @@ void fuse_conn_init(struct fuse_conn *fc, struct fuse= _mount *fm, fc->name_max =3D FUSE_NAME_LOW_MAX; fc->timeout.req_timeout =3D 0; =20 - if (IS_ENABLED(CONFIG_FUSE_PASSTHROUGH)) - fuse_backing_files_init(fc); - INIT_LIST_HEAD(&fc->mounts); list_add(&fm->fc_entry, &fc->mounts); fm->fc =3D fc; @@ -1439,9 +1436,11 @@ static void process_init_reply(struct fuse_mount *fm= , struct fuse_args *args, arg->max_stack_depth > 0 && arg->max_stack_depth <=3D FILESYSTEM_MAX_STACK_DEPTH && !(flags & FUSE_WRITEBACK_CACHE)) { - fc->passthrough =3D 1; - fc->max_stack_depth =3D arg->max_stack_depth; - fm->sb->s_stack_depth =3D arg->max_stack_depth; + if (fuse_backing_files_init(fc) =3D=3D 0) { + fc->passthrough =3D 1; + fc->max_stack_depth =3D arg->max_stack_depth; + fm->sb->s_stack_depth =3D arg->max_stack_depth; + } } if (flags & FUSE_NO_EXPORT_SUPPORT) fm->sb->s_export_op =3D &fuse_export_fid_operations; diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h index c13e1f9a2f12..e4ff28a4ff40 100644 --- a/include/uapi/linux/fuse.h +++ b/include/uapi/linux/fuse.h @@ -1139,6 +1139,7 @@ struct fuse_backing_map { struct fuse_backing_map) #define FUSE_DEV_IOC_BACKING_CLOSE _IOW(FUSE_DEV_IOC_MAGIC, 2, uint32_t) #define FUSE_DEV_IOC_SYNC_INIT _IO(FUSE_DEV_IOC_MAGIC, 3) +#define FUSE_DEV_IOC_BACKING_CLOSE_ALL _IO(FUSE_DEV_IOC_MAGIC, 4) =20 struct fuse_lseek_in { uint64_t fh; --=20 2.41.0 From nobody Sun Feb 8 01:51:48 2026 Received: from mail-m49197.qiye.163.com (mail-m49197.qiye.163.com [45.254.49.197]) (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 6BC72341055; 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charset="utf-8" To simplify crash recovery and reduce performance impact, backing_ids are not persisted across daemon restarts. However, when the daemon restarts and another process open the same FUSE file and assigning it the same backing file (with the same inode) will also cause the fuse_inode_uncached_io_start() function to fail due to a mismatch in the fb pointer. So Relax the validation in fuse_inode_uncached_io_start() to compare backing inodes instead of fuse_backing pointers. Reviewed-by: Amir Goldstein Signed-off-by: Chunsheng Luo --- fs/fuse/iomode.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/fuse/iomode.c b/fs/fuse/iomode.c index 3728933188f3..ca7619958b0d 100644 --- a/fs/fuse/iomode.c +++ b/fs/fuse/iomode.c @@ -90,7 +90,7 @@ int fuse_inode_uncached_io_start(struct fuse_inode *fi, s= truct fuse_backing *fb) spin_lock(&fi->lock); /* deny conflicting backing files on same fuse inode */ oldfb =3D fuse_inode_backing(fi); - if (fb && oldfb && oldfb !=3D fb) { + if (fb && oldfb && file_inode(oldfb->file) !=3D file_inode(fb->file)) { err =3D -EBUSY; goto unlock; } --=20 2.41.0