From 796aa0547557e63338657ed1c487906f9fac4c73 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Tue, 8 Sep 2026 17:53:20 -0600 Subject: [PATCH] io_uring/rw: end write accounting from ->ki_complete Commit b000145e9907 moved both the fsnotify calls and the write accounting out of the kiocb completion handler and into the io_req_rw_complete() task_work. However, only the fsnotify part actually needed to move as it may sleep. Ending the write accounting is just a percpu_up_read() on the superblock writers sem. Deferring it is a problem, because it makes dropping SB_FREEZE_WRITE protection depend on the ring owner getting to running task_work. But the task may be blocked in freeze_super(), causing it to never get to that: task io-wq worker -------------------------------------------------------------- io_write() io_kiocb_start_write() (takes sb_writers, hidden from lockdep by __sb_writers_release) write_iter() -> -EIOCBQUEUED ioctl(FS_IOC_SHUTDOWN) bdev_freeze() freeze_super() percpu_down_write() <- waits for the reader above io_write() kiocb_start_write() percpu_down_read() <- queued behind the writer io_complete_rw() queues io_req_rw_complete() <- never runs, task is in D state End the write from io_complete_rw() instead, and leave only the fsnotify calls in task_work. Reported-by: syzbot+2eb3d983669d3e49d4fa@syzkaller.appspotmail.com Cc: stable@vger.kernel.org Fixes: b000145e9907 ("io_uring/rw: defer fsnotify calls to task context") Signed-off-by: Jens Axboe --- io_uring/rw.c | 29 +++++++++++++++++++---------- 1 file changed, 19 insertions(+), 10 deletions(-) diff --git a/io_uring/rw.c b/io_uring/rw.c index 95106dd1d7eb..3e22f294bdf2 100644 --- a/io_uring/rw.c +++ b/io_uring/rw.c @@ -517,20 +517,25 @@ static void io_req_end_write(struct io_kiocb *req) } } -/* - * Trigger the notifications after having done some IO, and finish the write - * accounting, if any. - */ +/* Trigger the notifications after having done some IO. */ +static void io_req_io_notify(struct io_kiocb *req) +{ + struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw); + + if (rw->kiocb.ki_flags & IOCB_WRITE) + fsnotify_modify(req->file); + else + fsnotify_access(req->file); +} + +/* Finish write accounting and notify, for inline completions only. */ static void io_req_io_end(struct io_kiocb *req) { struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw); - if (rw->kiocb.ki_flags & IOCB_WRITE) { + if (rw->kiocb.ki_flags & IOCB_WRITE) io_req_end_write(req); - fsnotify_modify(req->file); - } else { - fsnotify_access(req->file); - } + io_req_io_notify(req); } static void __io_complete_rw_common(struct io_kiocb *req, long res) @@ -563,7 +568,7 @@ void io_req_rw_complete(struct io_tw_req tw_req, io_tw_token_t tw) { struct io_kiocb *req = tw_req.req; - io_req_io_end(req); + io_req_io_notify(req); if (req->flags & (REQ_F_BUFFER_SELECTED|REQ_F_BUFFER_RING)) req->cqe.flags |= io_put_kbuf(req, max(req->cqe.res, 0), NULL); @@ -577,6 +582,10 @@ static void io_complete_rw(struct kiocb *kiocb, long res) struct io_rw *rw = container_of(kiocb, struct io_rw, kiocb); struct io_kiocb *req = cmd_to_io_kiocb(rw); + /* ring owner may block in freeze_super() before task_work runs */ + if (kiocb->ki_flags & IOCB_WRITE) + io_req_end_write(req); + __io_complete_rw_common(req, res); io_req_set_res(req, io_fixup_rw_res(req, res), 0); req->io_task_work.func = io_req_rw_complete;