Messages in this thread | | | Date | Mon, 19 Jun 2023 14:43:56 -0600 | From | Jens Axboe <> | Subject | f2fs async buffered write patch |
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Hi,
I came across this patch in a news posting:
https://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs.git/commit/?h=dev&id=d618126911829523e35a61f4a5a4ad159b1b2c8d
which has me a bit worried. As far as I can tell, all that patch does is set FMODE_BUF_WASYNC, and then just hope that the lower layers handle the rest?
What happens if iocb->ki_flags & IOCB_NOWAIT is true, and now we do:
generic_perform_write(iocb, from) ... ->write_begin() <- does this block? ... ->write_end() <- or this one? ... balance_dirty_pages_ratelimited() <- this one surely does...
If you look just one level down the latter to balance_dirty_pages_ratelimited_flags(), you'll even see the 'flags' argument documented there.
This looks pretty haphazard and cannot possibly work as-is, so please get this reverted until f2fs is converted to iomap, or IOCB_NOWAIT is handled by generic_perform_write() and below.
-- Jens Axboe
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