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[37.188.168.3]) by smtp.gmail.com with ESMTPSA id o29sm23839337wra.5.2020.06.25.05.40.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 25 Jun 2020 05:40:19 -0700 (PDT) Date: Thu, 25 Jun 2020 14:40:17 +0200 From: Michal Hocko To: "Matthew Wilcox (Oracle)" Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-xfs@vger.kernel.org, dm-devel@redhat.com, Mikulas Patocka , Jens Axboe , NeilBrown Subject: Re: [PATCH 6/6] mm: Add memalloc_nowait Message-ID: <20200625124017.GL1320@dhcp22.suse.cz> References: <20200625113122.7540-1-willy@infradead.org> <20200625113122.7540-7-willy@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200625113122.7540-7-willy@infradead.org> X-Rspamd-Queue-Id: B624C180442CD X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu 25-06-20 12:31:22, Matthew Wilcox wrote: > Similar to memalloc_noio() and memalloc_nofs(), memalloc_nowait() > guarantees we will not sleep to reclaim memory. Use it to simplify > dm-bufio's allocations. memalloc_nowait is a good idea! I suspect the primary usecase would be vmalloc. > Signed-off-by: Matthew Wilcox (Oracle) [...] > @@ -877,7 +857,9 @@ static struct dm_buffer *__alloc_buffer_wait_no_callback(struct dm_bufio_client > */ > while (1) { > if (dm_bufio_cache_size_latch != 1) { > - b = alloc_buffer(c, GFP_NOWAIT | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN); > + unsigned nowait_flag = memalloc_nowait_save(); > + b = alloc_buffer(c, GFP_KERNEL | __GFP_NOMEMALLOC | __GFP_NOWARN); > + memalloc_nowait_restore(nowait_flag); This looks confusing though. I am not familiar with alloc_buffer and there is quite some tweaking around __GFP_NORETRY in alloc_buffer_data which I do not follow but GFP_KERNEL just struck my eyes. So why cannot we have alloc_buffer(GFP_NOWAIT | __GFP_NOMEMALLOC | __GFP_NOWARN); -- Michal Hocko SUSE Labs