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Thu, 18 Apr 2024 12:41:24 +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 iKYuIvQUIWYyfQAAD6G6ig (envelope-from ); Thu, 18 Apr 2024 12:41:24 +0000 Date: Thu, 18 Apr 2024 14:41:23 +0200 From: Oscar Salvador To: Miaohe Lin Cc: akpm@linux-foundation.org, muchun.song@linux.dev, david@redhat.com, vbabka@suse.cz, willy@infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] mm/hugetlb: fix DEBUG_LOCKS_WARN_ON(1) when dissolve_free_hugetlb_folio() Message-ID: References: <20240418022000.3524229-1-linmiaohe@huawei.com> <20240418022000.3524229-2-linmiaohe@huawei.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Spam-Level: X-Spamd-Result: default: False [-4.51 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; RCVD_VIA_SMTP_AUTH(0.00)[]; RCVD_TLS_ALL(0.00)[]; ARC_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; MISSING_XM_UA(0.00)[]; TO_DN_SOME(0.00)[]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; FUZZY_BLOCKED(0.00)[rspamd.com]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_SEVEN(0.00)[8]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:dkim,imap1.dmz-prg2.suse.org:helo,imap1.dmz-prg2.suse.org:rdns]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; DKIM_TRACE(0.00)[suse.de:+] X-Rspamd-Action: no action X-Rspamd-Queue-Id: 18E975CA7F X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Spam-Flag: NO X-Spam-Score: -4.51 On Thu, Apr 18, 2024 at 04:00:42PM +0800, Miaohe Lin wrote: > On 2024/4/18 12:05, Oscar Salvador wrote: > > On Thu, Apr 18, 2024 at 10:19:59AM +0800, Miaohe Lin wrote: > >> diff --git a/mm/hugetlb.c b/mm/hugetlb.c > >> index 26ab9dfc7d63..1da9a14a5513 100644 > >> --- a/mm/hugetlb.c > >> +++ b/mm/hugetlb.c > >> @@ -1788,7 +1788,8 @@ static void __update_and_free_hugetlb_folio(struct hstate *h, > >> destroy_compound_gigantic_folio(folio, huge_page_order(h)); > >> free_gigantic_folio(folio, huge_page_order(h)); > >> } else { > >> - INIT_LIST_HEAD(&folio->_deferred_list); > >> + if (!folio_test_hugetlb(folio)) > >> + INIT_LIST_HEAD(&folio->_deferred_list); > > > > Ok, it took me a bit to figure this out. > > > > So we basically init __deferred_list when we know that > > folio_put will not end up calling free_huge_folio > > because a previous call to remove_hugetlb_folio has already cleared the > > bit. > > > > Maybe Matthew thought that any folio ending here would not end up in > > free_huge_folio (which is the one fiddling subpool). > > > > I mean, fix looks good because if hugetlb flag is cleared, > > destroy_large_folio will go straight to free_the_page, but the > > whole thing is a bit subtle. > > AFAICS, this is the most straightforward way to fix the issue. Do you have any suggestions > on how to fix this in a more graceful way? Not from the top of my head. Anyway, I have been thinking for a while that this code needs some love, so I will check how this can be untangled. -- Oscar Salvador SUSE Labs