Commit 6e014c62 authored May 24, 2020 by Jens Axboe Committed by Theodore Ts'o Jun 03, 2020

ext4: don't block for O_DIRECT if IOCB_NOWAIT is set



Running with some debug patches to detect illegal blocking triggered the
extend/unaligned condition in ext4. If ext4 needs to extend the file (and
hence go to buffered IO), or if the app is doing unaligned IO, then ext4
asks the iomap code to wait for IO completion. If the caller asked for
no-wait semantics by setting IOCB_NOWAIT, then ext4 should return -EAGAIN
instead.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

Link: https://lore.kernel.org/r/76152096-2bbb-7682-8fce-4cb498bcd909@kernel.dk


Signed-off-by: Theodore Ts'o <tytso@mit.edu>

parent ba988903

fs/ext4/file.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -502,6 +502,12 @@ static ssize_t ext4_dio_write_iter(struct kiocb iocb, struct iov_iter from)
		if (ret <= 0)
		return ret;

		/* if we're going to block and IOCB_NOWAIT is set, return -EAGAIN */
		if ((iocb->ki_flags & IOCB_NOWAIT) && (unaligned_io \|\| extend)) {
		ret = -EAGAIN;
		goto out;
		}

		offset = iocb->ki_pos;
		count = ret;

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