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b=saBd+iO0MIUgoZ4T5DRBATueCRhVVjotyw4Csano7+W9Nl8UVMN/+rjwX48WDr72KVfR5S E1sM7zsp98SMCT+OnD8A+ABwz1TWwq/Hqj4J+azldEpAyvy2KrCzNaVgxg/6Gd5j+ig+I3 LZVbKW2vMHzHcsZmEZVArrao/1Xzwaw= X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 53F75140063 X-Rspam-User: Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=Nvidia.com header.s=selector2 header.b=LTCtw7Jb; dmarc=pass (policy=reject) header.from=nvidia.com; arc=pass ("microsoft.com:s=arcselector9901:i=1"); spf=pass (imf23.hostedemail.com: domain of jhubbard@nvidia.com designates 40.107.236.41 as permitted sender) smtp.mailfrom=jhubbard@nvidia.com X-Stat-Signature: bnixpngto8ufz3xg9dti753t895yjf1z X-HE-Tag: 1660768517-915769 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 8/17/22 05:09, Jason Gunthorpe wrote: >>> if (!ret) == if (ret != 0) >> >> Huh? Unless I'm misinterpretting you or am really behind on coffee >> if (!ret) is equivalent to if (ret == 0), not if (ret != 0). Although the !ret idiom is a huge, huge part of kernel coding practice, it also adds a slight bit of unnecessary mental translation (go ahead, flame me hard, I know I'm asking for it...but...see above, after all. Pixels have been spilt working through it). And also... > > Oh Dear, maybe I am still a bit jetlagged > > Regardless, it is confusingly written :) > ...this is a slightly tricky and unusual error case, so it helps to be extra clear by comparing against zero, and even adding a few short comments. How's this look to you: collected = collect_longterm_unpinnable_pages(&movable_page_list, nr_pages, pages); if (collected == 0) return 0; ret = migrate_longterm_unpinnable_pages(&movable_page_list, nr_pages, pages); /* If we got here, we have some unpinnable pages... */ if (ret == 0) { /* * ...and we successfully migrated those pages. Which means that * the caller should retry the operation now. */ ret = -EAGAIN; } return ret; thanks, -- John Hubbard NVIDIA