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Shutemov" To: Michal Hocko Cc: "Kirill A. Shutemov" , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] mm/shmem: Do not wait for lock_page() in shmem_unused_huge_shrink() Message-ID: <20180316122508.fv4edpx34hdqybwx@node.shutemov.name> References: <20180316105908.62516-1-kirill.shutemov@linux.intel.com> <20180316121303.GI23100@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180316121303.GI23100@dhcp22.suse.cz> User-Agent: NeoMutt/20180223 Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Fri, Mar 16, 2018 at 01:13:03PM +0100, Michal Hocko wrote: > On Fri 16-03-18 13:59:08, Kirill A. Shutemov wrote: > [..] > > @@ -498,31 +498,42 @@ static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo, > > continue; > > } > > > > - page = find_lock_page(inode->i_mapping, > > + page = find_get_page(inode->i_mapping, > > (inode->i_size & HPAGE_PMD_MASK) >> PAGE_SHIFT); > > if (!page) > > goto drop; > > > > + /* No huge page at the end of the file: nothing to split */ > > if (!PageTransHuge(page)) { > > - unlock_page(page); > > put_page(page); > > goto drop; > > } > > > > + /* > > + * Leave the inode on the list if we failed to lock > > + * the page at this time. > > + * > > + * Waiting for the lock may lead to deadlock in the > > + * reclaim path. > > + */ > > + if (!trylock_page(page)) { > > + put_page(page); > > + goto leave; > > + } > > Can somebody split the huge page after the PageTransHuge check and > before we lock it? Nope. Pin on the page is enough to prevent split. -- Kirill A. Shutemov