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From: Kent Overstreet To: Christoph Hellwig Cc: Yafang Shao , akpm@linux-foundation.org, viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, david@fromorbit.com, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 1/2] mm: Add memalloc_nowait_{save,restore} Message-ID: <5evd6n5ncanmyc2qtjpb44bd76xj7icitdf3g6xeb2eiofh6ht@eqm6r2ch4b3l> References: <20240812090525.80299-1-laoar.shao@gmail.com> <20240812090525.80299-2-laoar.shao@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Migadu-Flow: FLOW_OUT X-Stat-Signature: kw8z4djmcwapzb6winzno3bstezu3yer X-Rspamd-Queue-Id: 9DFF4C0006 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1723481313-59119 X-HE-Meta: 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 7WaxrDeL PgYhmRrd7C2PQoO4lKH/s9i/TTrPSlQTaOZgdyzbsrKsdrXPdChWcM0bokA83zM+ILgMtgEfwHokf/i8/tPwRtDGONUywMLV1+2LEvZSoKQp5gExK+G8XAzKiooIWfhJItsjOSGyzzK1B6zLCzTClZDt1Z9thI8fVqYcq5h/vVRkTw03qqk0boKRz7OTmzqpy4UEB2mL8fZ8JDFeZ5ndsuMsSnnzDspgBeJCtrbDOZKZ7gNocEummVAdBrpEpgZcDqFJh1Ys6cQVEgac= 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 Mon, Aug 12, 2024 at 04:37:58AM GMT, Christoph Hellwig wrote: > On Mon, Aug 12, 2024 at 05:05:24PM +0800, Yafang Shao wrote: > > The PF_MEMALLOC_NORECLAIM flag was introduced in commit eab0af905bfc > > ("mm: introduce PF_MEMALLOC_NORECLAIM, PF_MEMALLOC_NOWARN"). To complement > > this, let's add two helper functions, memalloc_nowait_{save,restore}, which > > will be useful in scenarios where we want to avoid waiting for memory > > reclamation. > > No, forcing nowait on callee contets is just asking for trouble. > Unlike NOIO or NOFS this is incompatible with NOFAIL allocations > and thus will lead to kernel crashes. No different from passing GFP_NOWAIT to mempoool_alloc(), and we're trying to get away from passing gfp flags directly for multiple reasons so we need it.