From: Joseph Qi joseph.qi@linux.alibaba.com
commit 54aa7f2330b82884f4a1afce0220add6e8312f8b upstream.
Heming reported a BUG when using io_uring doing link-cp on ocfs2. [1]
Do the following steps can reproduce this BUG: mount -t ocfs2 /dev/vdc /mnt/ocfs2 cp testfile /mnt/ocfs2/ ./link-cp /mnt/ocfs2/testfile /mnt/ocfs2/testfile.1 umount /mnt/ocfs2
Then umount will fail, and it outputs: umount: /mnt/ocfs2: target is busy.
While tracing umount, it blames mnt_get_count() not return as expected. Do a deep investigation for fget()/fput() on related code flow, I've finally found that fget() leaks since ocfs2 doesn't support nowait buffered read.
io_issue_sqe |-io_assign_file // do fget() first |-io_read |-io_iter_do_read |-ocfs2_file_read_iter // return -EOPNOTSUPP |-kiocb_done |-io_rw_done |-__io_complete_rw_common // set REQ_F_REISSUE |-io_resubmit_prep |-io_req_prep_async // override req->file, leak happens
This was introduced by commit a196c78b5443 in v5.18. Fix it by don't re-assign req->file if it has already been assigned.
[1] https://lore.kernel.org/ocfs2-devel/ab580a75-91c8-d68a-3455-40361be1bfa8@lin...
Fixes: a196c78b5443 ("io_uring: assign non-fixed early for async work") Cc: stable@vger.kernel.org Reported-by: Heming Zhao heming.zhao@suse.com Signed-off-by: Joseph Qi joseph.qi@linux.alibaba.com Cc: Xiaoguang Wang xiaoguang.wang@linux.alibaba.com Link: https://lore.kernel.org/r/20230228045459.13524-1-joseph.qi@linux.alibaba.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- io_uring/io_uring.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -1728,7 +1728,7 @@ int io_req_prep_async(struct io_kiocb *r const struct io_op_def *def = &io_op_defs[req->opcode];
/* assign early for deferred execution for non-fixed file */ - if (def->needs_file && !(req->flags & REQ_F_FIXED_FILE)) + if (def->needs_file && !(req->flags & REQ_F_FIXED_FILE) && !req->file) req->file = io_file_get_normal(req, req->cqe.fd); if (!def->prep_async) return 0;