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authorJens Axboe <axboe@kernel.dk>2023-10-24 23:39:06 +0300
committerJens Axboe <axboe@kernel.dk>2023-10-25 17:02:29 +0300
commit838b35bb6a89c36da07ca39520ec071d9250334d (patch)
tree598273089e020a7108b9957be3d277d96f09df0a /io_uring
parent7644b1a1c9a7ae8ab99175989bfc8676055edb46 (diff)
downloadlinux-838b35bb6a89c36da07ca39520ec071d9250334d.tar.xz
io_uring/rw: disable IOCB_DIO_CALLER_COMP
If an application does O_DIRECT writes with io_uring and the file system supports IOCB_DIO_CALLER_COMP, then completions of the dio write side is done from the task_work that will post the completion event for said write as well. Whenever a dio write is done against a file, the inode i_dio_count is elevated. This enables other callers to use inode_dio_wait() to wait for previous writes to complete. If we defer the full dio completion to task_work, we are dependent on that task_work being run before the inode i_dio_count can be decremented. If the same task that issues io_uring dio writes with IOCB_DIO_CALLER_COMP performs a synchronous system call that calls inode_dio_wait(), then we can deadlock as we're blocked sleeping on the event to become true, but not processing the completions that will result in the inode i_dio_count being decremented. Until we can guarantee that this is the case, then disable the deferred caller completions. Fixes: 099ada2c8726 ("io_uring/rw: add write support for IOCB_DIO_CALLER_COMP") Reported-by: Andres Freund <andres@anarazel.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'io_uring')
-rw-r--r--io_uring/rw.c9
1 files changed, 0 insertions, 9 deletions
diff --git a/io_uring/rw.c b/io_uring/rw.c
index c8c822fa7980..807d83ab756e 100644
--- a/io_uring/rw.c
+++ b/io_uring/rw.c
@@ -913,15 +913,6 @@ int io_write(struct io_kiocb *req, unsigned int issue_flags)
kiocb_start_write(kiocb);
kiocb->ki_flags |= IOCB_WRITE;
- /*
- * For non-polled IO, set IOCB_DIO_CALLER_COMP, stating that our handler
- * groks deferring the completion to task context. This isn't
- * necessary and useful for polled IO as that can always complete
- * directly.
- */
- if (!(kiocb->ki_flags & IOCB_HIPRI))
- kiocb->ki_flags |= IOCB_DIO_CALLER_COMP;
-
if (likely(req->file->f_op->write_iter))
ret2 = call_write_iter(req->file, kiocb, &s->iter);
else if (req->file->f_op->write)