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Sun, 1 Sep 2024 20:18:13 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id 60eQEQXM1GbxfgAAD6G6ig (envelope-from ); Sun, 01 Sep 2024 20:18:13 +0000 Message-ID: <210c45bd-f7f4-4ecc-92fc-4059c32d8f56@suse.cz> Date: Sun, 1 Sep 2024 22:18:13 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 3/3] mm: warn about illegal __GFP_NOFAIL usage in a more appropriate location and manner Content-Language: en-US To: Barry Song <21cnbao@gmail.com>, akpm@linux-foundation.org, linux-mm@kvack.org, virtualization@lists.linux.dev Cc: david@redhat.com, 42.hyeyoo@gmail.com, cl@linux.com, hailong.liu@oppo.com, hch@infradead.org, iamjoonsoo.kim@lge.com, mhocko@suse.com, penberg@kernel.org, rientjes@google.com, roman.gushchin@linux.dev, torvalds@linux-foundation.org, urezki@gmail.com, v-songbaohua@oppo.com, laoar.shao@gmail.com References: <20240830202823.21478-1-21cnbao@gmail.com> <20240830202823.21478-4-21cnbao@gmail.com> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; 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charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Action: no action X-Stat-Signature: bwbzza3zg3i68j7zezudch7b5sikigc1 X-Rspamd-Queue-Id: 5E5B81C0005 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1725221895-984493 X-HE-Meta: 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 EWzTL/iX z9St5dcS5vUEPJiAtcoqkPwKgk3nSjItzrsCPZxf7/VFmRcTDGLGQ37fObbyt9iHRfzJAlYQoq6WQa+e6BD6adf/l7EFNz367S5rZl8mAFbO/vm9gQT/uFY3sKafqsLep7jeWz1ltpjfvLNLIMZKZ6KwGyPTOCxRoScjo0Wkhxq+5ZYuWb81TU6ggaiBfGItrr6eFIQdL+q7rELb025DfD/S0FPo9iI0IzTbFNNIb/c8oP24akk+JhDSyh9pl4lBiQCzy+4wp2dctNSWWmQHunY5tYqCnijqZL4wUZlaXXRnmLQKWCEe1zV0wDSr+zvxGgKf72Omq1Y/BjrBsGt3+s1S6ofuDMZuIrQasCc2vk2tQOh+oe+ijxvDcf6hGqkhuD0i8lXc6ZlRmYjeRg75oFf2UfD41C1VirjX3UD2CzwyxLFiFpLzu7g2qjjHvRSdfpWgz48lyGhlZShAUWTKggLnsniZEWX/uBJJ8+Om6EmdbEOE= 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: List-Subscribe: List-Unsubscribe: On 8/30/24 22:28, Barry Song wrote: > From: Barry Song > > Three points for this change: > > 1. We should consolidate all warnings in one place. Currently, the > order > 1 warning is in the hotpath, while others are in less > likely scenarios. Moving all warnings to the slowpath will reduce > the overhead for order > 1 and increase the visibility of other > warnings. > > 2. We currently have two warnings for order: one for order > 1 in > the hotpath and another for order > costly_order in the laziest > path. I suggest standardizing on order > 1 since it’s been in > use for a long time. > > 3. We don't need to check for __GFP_NOWARN in this case. __GFP_NOWARN > is meant to suppress allocation failure reports, but here we're > dealing with bug detection, not allocation failures. So replace > WARN_ON_ONCE_GFP by WARN_ON_ONCE. > > Suggested-by: Vlastimil Babka > Signed-off-by: Barry Song Reviewed-by: Vlastimil Babka Thanks! > --- > mm/page_alloc.c | 50 ++++++++++++++++++++++++------------------------- > 1 file changed, 25 insertions(+), 25 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index c81ee5662cc7..e790b4227322 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -3033,12 +3033,6 @@ struct page *rmqueue(struct zone *preferred_zone, > { > struct page *page; > > - /* > - * We most definitely don't want callers attempting to > - * allocate greater than order-1 page units with __GFP_NOFAIL. > - */ > - WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1)); > - > if (likely(pcp_allowed_order(order))) { > page = rmqueue_pcplist(preferred_zone, zone, order, > migratetype, alloc_flags); > @@ -4175,6 +4169,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, > { > bool can_direct_reclaim = gfp_mask & __GFP_DIRECT_RECLAIM; > bool can_compact = gfp_compaction_allowed(gfp_mask); > + bool nofail = gfp_mask & __GFP_NOFAIL; > const bool costly_order = order > PAGE_ALLOC_COSTLY_ORDER; > struct page *page = NULL; > unsigned int alloc_flags; > @@ -4187,6 +4182,25 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, > unsigned int zonelist_iter_cookie; > int reserve_flags; > > + if (unlikely(nofail)) { > + /* > + * We most definitely don't want callers attempting to > + * allocate greater than order-1 page units with __GFP_NOFAIL. > + */ > + WARN_ON_ONCE(order > 1); > + /* > + * Also we don't support __GFP_NOFAIL without __GFP_DIRECT_RECLAIM, > + * otherwise, we may result in lockup. > + */ > + WARN_ON_ONCE(!can_direct_reclaim); > + /* > + * PF_MEMALLOC request from this context is rather bizarre > + * because we cannot reclaim anything and only can loop waiting > + * for somebody to do a work for us. > + */ > + WARN_ON_ONCE(current->flags & PF_MEMALLOC); > + } > + > restart: > compaction_retries = 0; > no_progress_loops = 0; > @@ -4404,29 +4418,15 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, > * Make sure that __GFP_NOFAIL request doesn't leak out and make sure > * we always retry > */ > - if (gfp_mask & __GFP_NOFAIL) { > + if (unlikely(nofail)) { > /* > - * All existing users of the __GFP_NOFAIL are blockable, so warn > - * of any new users that actually require GFP_NOWAIT > + * Lacking direct_reclaim we can't do anything to reclaim memory, > + * we disregard these unreasonable nofail requests and still > + * return NULL > */ > - if (WARN_ON_ONCE_GFP(!can_direct_reclaim, gfp_mask)) > + if (!can_direct_reclaim) > goto fail; > > - /* > - * PF_MEMALLOC request from this context is rather bizarre > - * because we cannot reclaim anything and only can loop waiting > - * for somebody to do a work for us > - */ > - WARN_ON_ONCE_GFP(current->flags & PF_MEMALLOC, gfp_mask); > - > - /* > - * non failing costly orders are a hard requirement which we > - * are not prepared for much so let's warn about these users > - * so that we can identify them and convert them to something > - * else. > - */ > - WARN_ON_ONCE_GFP(costly_order, gfp_mask); > - > /* > * Help non-failing allocations by giving some access to memory > * reserves normally used for high priority non-blocking