From: Zizhi Wo Date: Sat, 4 Jul 2026 01:53:20 +0000 (+0800) Subject: smb: client: fix busy dentry warning on unmount after DIO X-Git-Tag: v7.2-rc3~22^2~9 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=75f5c412fa867efa0bf9b646bffe0d912109e84a;p=thirdparty%2Fkernel%2Flinux.git smb: client: fix busy dentry warning on unmount after DIO Commit c68337442f03 ("cifs: Fix busy dentry used after unmounting") fixed the issue in cifs where deferred close of a file led to a dentry reference count not being released in umount, by flushing deferredclose_wq in cifs_kill_sb() to solve it. However, the cifs DIO path suffers from the same busy-dentry problem caused by a delayed dentry reference-count release: [dio] [cifsd] [close + umount] netfs_unbuffered_write_iter_locked ... cifs_demultiplex_thread netfs_unbuffered_write cifs_issue_write netfs_wait_for_in_progress_stream [1] ... netfs_write_subrequest_terminated netfs_subreq_clear_in_progress netfs_wake_collector // wake [1] netfs_put_subrequest netfs_put_request queue_work(system_dfl_wq, xxx) [2] // dio write return cifs_close _cifsFileInfo_put // cfile->count 2->1 --cfile->count [3] // umount cifs_kill_sb kill_anon_super // warning triggered! shrink_dcache_for_umount [4] [system_dfl_wq] [5] netfs_free_request ... _cifsFileInfo_put // cfile->count 1->0 --cfile->count queue_work(fileinfo_put_wq, xxx) [fileinfo_put_wq] [6] cifsFileInfo_put_work cifsFileInfo_put_final dput If the umount path is triggered before [5], it results warning: BUG: Dentry 00000000eab1f070{i=9a917b66ae404fec,n=test} still in use (1) [unmount of cifs cifs] The existing per-inode ictx->io_count wait in cifs_evict_inode() does not help: it lives in the inode eviction path, which runs after shrink_dcache_for_umount() has already warned about the busy dentries. Fix it by adding a per-superblock outstanding-rreq counter that is incremented in cifs_init_request() and decremented in cifs_free_request(). In cifs_kill_sb(), before kill_anon_super(), wait for this counter to reach 0 - which guarantees that all cleanup_work for this sb have run and thus all relevant cfile puts are queued on fileinfo_put_wq or serverclose_wq. Then drain the workqueue so the dentry refs are dropped. This is a targeted wait, not a flush of the system-wide system_dfl_wq. Fixes: 340cea84f691c ("cifs: open files should not hold ref on superblock") Signed-off-by: Zizhi Wo Signed-off-by: Steve French --- diff --git a/fs/smb/client/cifs_fs_sb.h b/fs/smb/client/cifs_fs_sb.h index 84e7e366b0ff..d6494e1d93cc 100644 --- a/fs/smb/client/cifs_fs_sb.h +++ b/fs/smb/client/cifs_fs_sb.h @@ -56,6 +56,7 @@ struct cifs_sb_info { struct smb3_fs_context *ctx; atomic_t active; atomic_t mnt_cifs_flags; + atomic_t outstanding_rreq; /* nr of rreqs not yet fully deinitialized */ struct delayed_work prune_tlinks; struct rcu_head rcu; diff --git a/fs/smb/client/cifsfs.c b/fs/smb/client/cifsfs.c index ea4fc0fa68ca..4df6ca03a8de 100644 --- a/fs/smb/client/cifsfs.c +++ b/fs/smb/client/cifsfs.c @@ -311,6 +311,18 @@ static void cifs_kill_sb(struct super_block *sb) /* Wait for all opened files to release */ flush_workqueue(deferredclose_wq); + /* + * Wait for all in-flight netfs I/O requests to finish their + * cleanup_work so that any cifsFileInfo final puts they queue + * to fileinfo_put_wq/serverclose_wq have been queued, then + * drain the workqueue so the cfile dentry refs are dropped to + * avoid the busy dentry warning. + */ + wait_var_event(&cifs_sb->outstanding_rreq, + !atomic_read(&cifs_sb->outstanding_rreq)); + flush_workqueue(serverclose_wq); + flush_workqueue(fileinfo_put_wq); + /* finally release root dentry */ dput(cifs_sb->root); cifs_sb->root = NULL; diff --git a/fs/smb/client/connect.c b/fs/smb/client/connect.c index 85aec302c89e..a187398fbabd 100644 --- a/fs/smb/client/connect.c +++ b/fs/smb/client/connect.c @@ -3485,6 +3485,7 @@ int cifs_setup_cifs_sb(struct cifs_sb_info *cifs_sb) spin_lock_init(&cifs_sb->tlink_tree_lock); cifs_sb->tlink_tree = RB_ROOT; + atomic_set(&cifs_sb->outstanding_rreq, 0); cifs_dbg(FYI, "file mode: %04ho dir mode: %04ho\n", ctx->file_mode, ctx->dir_mode); diff --git a/fs/smb/client/file.c b/fs/smb/client/file.c index 6a4aa57d58c3..968740e7c9c3 100644 --- a/fs/smb/client/file.c +++ b/fs/smb/client/file.c @@ -288,6 +288,7 @@ static int cifs_init_request(struct netfs_io_request *rreq, struct file *file) return smb_EIO1(smb_eio_trace_not_netfs_writeback, rreq->origin); } + atomic_inc(&cifs_sb->outstanding_rreq); return 0; } @@ -309,9 +310,13 @@ static void cifs_rreq_done(struct netfs_io_request *rreq) static void cifs_free_request(struct netfs_io_request *rreq) { struct cifs_io_request *req = container_of(rreq, struct cifs_io_request, rreq); + struct cifs_sb_info *cifs_sb = CIFS_SB(rreq->inode->i_sb); if (req->cfile) cifsFileInfo_put(req->cfile); + + if (atomic_dec_and_test(&cifs_sb->outstanding_rreq)) + wake_up_var(&cifs_sb->outstanding_rreq); } static void cifs_free_subrequest(struct netfs_io_subrequest *subreq)