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([2620:10d:c090:400::5:32c6]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-1f44c79d046sm373525ad.72.2024.05.23.14.16.40 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 23 May 2024 14:16:40 -0700 (PDT) Message-ID: <024b9a30-ad3b-4063-b5c8-e6c948ad6b2e@kernel.dk> Date: Thu, 23 May 2024 15:16:38 -0600 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/filemap: invalidating pages is still necessary when io with IOCB_NOWAIT To: Matthew Wilcox , Liu Wei Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, Goldwyn Rodrigues , Christoph Hellwig , Jan Kara , linux-fsdevel@vger.kernel.org References: <20240513132339.26269-1-liuwei09@cestc.cn> Content-Language: en-US From: Jens Axboe In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 5/23/24 3:08 PM, Matthew Wilcox wrote: > On Mon, May 13, 2024 at 09:23:39PM +0800, Liu Wei wrote: >> After commit (6be96d3ad3 fs: return if direct I/O will trigger writeback), > > If you're reporting problems with a particular commit, it's good form > to cc the people who actually wrote that commit. Yeah indeed... >> when we issuing AIO with direct I/O and IOCB_NOWAIT on a block device, the >> process context will not be blocked. >> >> However, if the device already has page cache in memory, EAGAIN will be >> returned. And even when trying to reissue the AIO with direct I/O and >> IOCB_NOWAIT again, we consistently receive EAGAIN. -EAGAIN doesn't mean "just try again and it'll work". >> Maybe a better way to deal with it: filemap_fdatawrite_range dirty pages >> with WB_SYNC_NONE flag, and invalidate_mapping_pages unmapped pages at >> the same time. >> >> Signed-off-by: Liu Wei >> --- >> mm/filemap.c | 9 ++++++++- >> 1 file changed, 8 insertions(+), 1 deletion(-) >> >> diff --git a/mm/filemap.c b/mm/filemap.c >> index 30de18c4fd28..1852a00caf31 100644 >> --- a/mm/filemap.c >> +++ b/mm/filemap.c >> @@ -2697,8 +2697,15 @@ int kiocb_invalidate_pages(struct kiocb *iocb, size_t count) >> >> if (iocb->ki_flags & IOCB_NOWAIT) { >> /* we could block if there are any pages in the range */ >> - if (filemap_range_has_page(mapping, pos, end)) >> + if (filemap_range_has_page(mapping, pos, end)) { >> + if (mapping_needs_writeback(mapping)) { >> + __filemap_fdatawrite_range(mapping, >> + pos, end, WB_SYNC_NONE); >> + } I don't think WB_SYNC_NONE tells it not to block, it just says not to wait for it... So this won't work as-is. >> + invalidate_mapping_pages(mapping, >> + pos >> PAGE_SHIFT, end >> PAGE_SHIFT); >> return -EAGAIN; >> + } >> } else { >> ret = filemap_write_and_wait_range(mapping, pos, end); >> if (ret) >> -- >> 2.42.1 >> >> >> -- Jens Axboe