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dkim=pass header.d=Nvidia.com header.s=selector2 header.b=iSTV3SL+; dmarc=pass (policy=reject) header.from=nvidia.com; spf=none (imf01.hostedemail.com: domain of apopple@nvidia.com has no SPF policy when checking 40.107.236.71) smtp.mailfrom=apopple@nvidia.com X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: DC4774007B X-Stat-Signature: ok3mr5fotpc74wffronrn9dfef9959wb X-HE-Tag: 1654261123-778494 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: Matthew Wilcox writes: > On Fri, Jun 03, 2022 at 05:12:33PM +1000, Alistair Popple wrote: >> +++ b/mm/filemap.c >> @@ -3168,8 +3168,9 @@ vm_fault_t filemap_fault(struct vm_fault *vmf) >> VM_BUG_ON_FOLIO(!folio_contains(folio, index), folio); >> >> /* >> - * We have a locked page in the page cache, now we need to check >> - * that it's up-to-date. If not, it is going to be due to an error. >> + * We have a locked page in the page cache. Check that it's up-to-date. >> + * If not it is because there was no page in the page cache (only likely >> + * in the case of MADV_RANDOM) or due to error. > > The comment is correct, but the code is buggy! Ha! > We should be calling page_cache_ra_order() in do_sync_mmap_readahead(), > even if VM_RAND_READ is set (or !ra_pages, or mmap_miss is high). > At least for one page. That would allow us to drop the FGP_FOR_MMAP > flag as page_cache_ra_order() will instantiate a folio for us. > > Do you want to write that patch or should I do it? Thanks for the pointers, I can do it. - Alistair