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a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1724317800; bh=tsy6eCpRKU9g9aZk/LywKrBSdPQUpsF/AQqQWlf9+TY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=QjxPmlQCNR/ZFTR41kqsfhmt9uTmnGUAADTmp2uAK7+YJzWiqC+SX2qWLBxb5k2Iv pXO/uElA43UGzHdF8ya9/1poEHEPuDAN4nJpKvtyuq+3VUgt3PYSKSJFWocGXLuNYc 5T1XONASu+VviHx2asvZJez3pH3e2/o5bbjwGEmVTpjxi0XjBz87mHzPpKk/WHsiPm nMibElTl0NZF+DG8nWi/E6f3FfIUIxb+zTo2MM9B7aoLi0phHTmR1otLuvsyjwBqnW +ev8Veo20KR9eLe1yHqVZsmk90PqDLOU8yrpj1ySXxEavgMvIbPk9nID3X04eSylnE X5+f93lsNVLOQ== Date: Thu, 22 Aug 2024 11:09:55 +0200 From: Christian Brauner To: Michal Hocko Cc: Christoph Hellwig , Yafang Shao , Andrew Morton , viro@zeniv.linux.org.uk, jack@suse.cz, david@fromorbit.com, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Kent Overstreet Subject: Re: [PATCH] mm: document risk of PF_MEMALLOC_NORECLAIM Message-ID: <20240822-unlustig-rauslassen-484a9d3af358@brauner> References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: B1446180011 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: f4ksswj3pwr6tbptboawph9riiwxht9r X-HE-Tag: 1724608007-869080 X-HE-Meta: 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 2FQ6i89n fClDVKRpk6ppbkkmLysxIOwpnYTzES8edGjZJxA4QW4ieKi3YUqbQGKJ65RiOLvAJwFPNM7yd9wsqzEvpN1OgxAikW/uPnC7nPmpNUHuO7OhJjHaURqL/AV+1vMCMoFlTwg9aZFjMA8apC9xkc56wEB7JdX4GSWjsWTsj2o/57kIGkK5L0KhbKpjVa+8upKIPQP4IO9PJ0bdgeYkmz+jfqAHiBK0iIIZgacJ68cU0M6uoQUoP+DL4DliCwqnRsinTdFJAav0+y4x0vy5o54KPO0L3h4vwQUhsOmb7Fd+vjBhowhp451cWqjzdVecefMZr5d9/aVpdA5o1GvYrgTBGILzLDk8DEyQC+3x5hDe1S2VU/VDxjVmazKukrS6t3Iy9s7AKwayHeE548E528dBwbmQ3yfUGjMRJnt11+2m0udVcygrBuzcdkmUqBQ== 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 Wed, Aug 21, 2024 at 02:37:33PM GMT, Michal Hocko wrote: > On Wed 21-08-24 04:44:03, Christoph Hellwig wrote: > > On Fri, Aug 16, 2024 at 10:54:37AM +0200, Michal Hocko wrote: > > > Yes, I think we should kill it before it spreads even more but I would > > > not like to make the existing user just broken. I have zero visibility > > > and understanding of the bcachefs code but from a quick look at __bch2_new_inode > > > it shouldn't be really terribly hard to push GFP_NOWAIT flag there > > > directly. > > > > > I don't understand that sentence. You're adding the gfp_t argument to > > it, which to mean counts as pushing it there directly. > > Sorry, what I meant to say is that pushing GFP_NOWAIT directly seem fine > unless I have missed some hidden corners down the call path which would > require a scope flag to override a hardcoded gfp flag. > > > > It would require inode_init_always_gfp variant as well (to not > > > touch all existing callers that do not have any locking requirements but > > > I do not see any other nested allocations. > > > > inode_init_always only has 4 callers, so I'd just add the gfp_t > > argument. Otherwise this looks good modulo the fix your posted: > > > > Acked-by: Christoph Hellwig > > Thanks. I will wait for more review and post this as a real patch. I > would really appreciate any help with actual testing. Ugh, I really don't like that we have to add a flag argument especially for an api that's broken but fine.