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Fri, 30 Jan 2026 17:05:45 -0800 (PST) MIME-Version: 1.0 References: <2026012715-mantra-pope-9431@gregkh> <20260128045954.GS3183987@ZenIV> <20260129032335.GT3183987@ZenIV> <20260129225433.GU3183987@ZenIV> <20260130070424.GV3183987@ZenIV> <20260130235743.GW3183987@ZenIV> In-Reply-To: <20260130235743.GW3183987@ZenIV> From: Samuel Wu Date: Fri, 30 Jan 2026 17:05:34 -0800 X-Gm-Features: AZwV_Qi-TVApb-UR_yhUuzDZcqy8acCYfKVdTsorIhJOL99wmGwpM0Som40uK5A Message-ID: Subject: Re: [PATCH v4 00/54] tree-in-dcache stuff To: Al Viro Cc: Greg KH , linux-fsdevel@vger.kernel.org, torvalds@linux-foundation.org, brauner@kernel.org, jack@suse.cz, raven@themaw.net, miklos@szeredi.hu, neil@brown.name, a.hindborg@kernel.org, linux-mm@kvack.org, linux-efi@vger.kernel.org, ocfs2-devel@lists.linux.dev, kees@kernel.org, rostedt@goodmis.org, linux-usb@vger.kernel.org, paul@paul-moore.com, casey@schaufler-ca.com, linuxppc-dev@lists.ozlabs.org, john.johansen@canonical.com, selinux@vger.kernel.org, borntraeger@linux.ibm.com, bpf@vger.kernel.org, clm@meta.com, android-kernel-team Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam11 X-Stat-Signature: xzzzf7u68k1bn49ucn7c683iyfhwfi5j X-Rspam-User: X-Rspamd-Queue-Id: CD2BBC0004 X-HE-Tag: 1769821547-706655 X-HE-Meta: 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 xxbZvtQL g/sSpKl5s/E4EzxRlc7Jr3+saYUvlknXf3S/NAspPl4knMuYCsqcSbYnQdMXc0GkkKpcGkU3fkvC7ekC3RDEFVCPVid7nrRxxEJ66HViuiiGFXrDhR4XlKb9jqxJW8V4f1YwgVUburM0u6KgiOkBfOp/q+rNbpQY17Rqs16/EPR5DzImSIuQrZ0pIj2eTSpxCjE75immAW2wZ8DSLlurMeReJMxh+9+/P7Jc1J9Q011NeuOyN5TiKK6pY/ZT7H5gAERguEjqIfZ82/M5wy0WWPWusS9sbSKHBnDyR/ImrE6CiEsNlWjr2OFXRFauLWDasokcSHE3iN/AniTtkWHeAg123G6s8+kPRfmmf0rx1BZAeaiC7tbxn7fxSdeZtC5PP/hfT X-Bogosity: Ham, tests=bogofilter, spamicity=0.043268, 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, Jan 30, 2026 at 3:55=E2=80=AFPM Al Viro w= rote: > So we have something that does O_NDELAY opens of ep0 *and* does not retry= on > EAGAIN? > > How lovely... Could you slap > WARN_ON(ret =3D=3D -EAGAIN); > right before that > if (ret < 0) > return ret; Surprisingly ret =3D=3D 0 every time, so no difference in dmesg logs with this addition. > in there and see which process is doing that? Regression is a regression= , > odd userland or not, but I would like to see what is that userland actual= ly > trying to do there. > > *grumble* > > IMO at that point we have two problems - one is how to avoid a revert of = the > tail of tree-in-dcache series, another is how to deal with quite real > preexisting bugs in functionfs. > > Another thing to try (not as a suggestion of a fix, just an attempt to fi= gure > out how badly would the things break): in current mainline replace that > ffs_mutex_lock(&ffs->mutex, file->f_flags & O_NONBLOCK) > in ffs_ep0_open() with > ffs_mutex_lock(&ffs->mutex, false) > and see how badly do the things regress for userland. Again, I'm not say= ing > that this is a fix - just trying to get some sense of what's the userland > is doing. Ergo this didn't make a difference either.