Messages in this thread | | | Date | Mon, 26 Jun 2023 15:31:57 +0800 | Subject | Re: f2fs async buffered write patch | From | Yangtao Li <> |
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+cc willy@infradead.org
On 2023/6/20 4:43, Jens Axboe wrote:
> 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?
Most file systems have not been changed to the iomap method,
and the generic_perform_write method is still used. So it seems
reasonable to make IOCB_NOWAIT be handled correctly by the
generic_perform_write function. This means that we need to modify
several places mentioned by Jens in the generic_perform_write function,
and need to pass AOP_FLAG_xxx or iocb into write_begin.
I noticed that Matthew Wilcox removed the flags parameter in write_begin
in a previous commit, maybe we can add it back?
Thx
> ... > ->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. >
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