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Wong" , Christoph Hellwig , Alexei Starovoitov , Daniel Borkmann , Meta kernel team , bpf@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, syzbot+09b7d050e4806540153d@syzkaller.appspotmail.com, Christoph Hellwig Subject: Re: [PATCH bpf v2] lib/buildid: use __kernel_read() for sleepable context Message-ID: References: <20251218205505.2415840-1-shakeel.butt@linux.dev> <3lf3ed3xn2oaenvlqjmypuewtm6gakzbecc7kgqsadggyvdtkr@uyw4boj6igqu> <64muytpsnwmjcnc5szbz4gfnh2owgorsfdl5zmomtykptfry4s@tuajoyqmulqc> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: r9zakzaq71mgwsmiritreq58cqkwpy99 X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 4287640009 X-HE-Tag: 1766381627-352334 X-HE-Meta: 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 3o89YmRo nhG+YO74nVAjo2V9H5Up2HTcqJMVzmEAG8AJL6ZB42DP8/SbtMoGS7nucoVHyFRbDrsXF8suG38jO4dwojfb9bDF/VPtU1hpSgA6DSNyFOzNVlUSqSVEnLGdxZm1DfqoenZB13LDKKI9YiCDeUc/NHXndz6VJ6/ZpzK+igOYTw1cVSwbmFQaFQfbZobzIU/n58q0+/pewQBop7J6PPR7xNqsbgK6fxkkHjSZiqedMsE2cW4p2OOEO93exSGT+cun1/30hAJ4BkDnm/zn6/Wd/ivjedCm5n66t6Kj8brlLeLALfBNUOBDYFXHakeMkgjSF46COcHaiw/7YCNnO75gPKQhF0NtRNk5wtTuHYAU4UsflgECkYNfTVYv/veJLfyNwhCCjb4NEgOySjLa+rEx0te6X9V1kIX2xTecew/viDBLgoN4= 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 Fri, Dec 19, 2025 at 09:42:13AM -0800, Andrii Nakryiko wrote: > From a user perspective, I'd very much appreciate it if I get exactly > the requested amount of bytes from freader_fetch_sync(), so yeah, > let's please keep the loop. It does seem that ret <= 0 handling is > correct and should not result in an endless loop. No, you don't understand. If __kernel_read() doesn't get all the data in one call, it's not there to get. If a partial amount of data is useful (I suspect not), we can return it, otherwise an error is the way to go. The loop just betrays a lack of understanding of the VFS.