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Wed, 4 Nov 2026 21:14:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793826860; bh=ulWAa08tPZnJZAAMojZfgqs4wxYXZkHD77FK42yiGkc=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=gICWh0N0cBEP36qoPjK07EDc0Aojrv63Cx+pq3ht7lC1Swqoe5+i3NPMXMP1HLqAh aYFDImUWgb2oQZfvZy0Eomed2z9bppjTMLZJqaCJ+P/lVF/sMbBDXyuQTYMAX6jaEG PZ2WLVcqSv9VuBvnWcTH3x8qTM6W0XC/ec65sI7vf6cdAdfTZxwUHxtQYl9brUxiQ+ dMCuHf59LCoq+BPf/+eWD45uHwN16HzFpn4iF3C3dDC4Tki7Nt0/cDmwKsfuapAQM6 WJY+xD/1Nj4i6s+oj2j1TqT1hys8Qp60ucvc7zwo51H/qzcJ2edAoUx8uzmvP8dUPB VqHIpYrdBBhDw== From: Christian Brauner To: linux-fsdevel@vger.kernel.org Cc: Linus Torvalds , Jann Horn , Josef Bacik , Chris Mason , Jeff Layton , NeilBrown , Eric Dumazet , Thomas Gleixner , Al Viro , Jonathan Corbet , Christoph Hellwig , Greg Kroah-Hartman , Joel Granados , Kees Cook , Jan Kara , Jan Kara , linux-kernel@vger.kernel.org, linux-nfs@vger.kernel.org, linux-acpi@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-s390@vger.kernel.org, linux-scsi@vger.kernel.org, linux-um@lists.infradead.org, linux-wireless@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, netdev@vger.kernel.org, ntfs3@lists.linux.dev, platform-driver-x86@vger.kernel.org, coreteam@netfilter.org, kexec@lists.infradead.org, linux-pci@vger.kernel.org, linux-sound@vger.kernel.org, netfilter-devel@vger.kernel.org, dri-devel@lists.freedesktop.org, ibm-acpi-devel@lists.sourceforge.net, jfs-discussion@lists.sourceforge.net, linux-alpha@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-cifs@vger.kernel.org, linux-fbdev@vger.kernel.org, linux-hwmon@vger.kernel.org, linux-mm@kvack.org, linux-sh@vger.kernel.org, linux-usb@vger.kernel.org, samba-technical@lists.samba.org, sparclinux@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-doc@vger.kernel.org, linux-serial@vger.kernel.org, linux-atm-general@lists.sourceforge.net, Takashi Iwai , linux-input@vger.kernel.org, linux-raid@vger.kernel.org, linux-ext4@vger.kernel.org, linux-modules@vger.kernel.org, linux-debuggers@vger.kernel.org, "Christian Brauner (Amutable)" , Chuck Lever Subject: [PATCH RESEND v2 12/13] samples/kfifo: let procfs copy out reads Date: Wed, 4 Nov 2026 22:14:06 +0100 Message-ID: <20261104-work-procfs-net-v2-12-221e2437fed1@kernel.org> In-Reply-To: <20261104-work-procfs-net-v2-0-221e2437fed1@kernel.org> References: <20261104-work-procfs-net-v2-0-221e2437fed1@kernel.org> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , Precedence: list X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" X-Mailer: b4 0.17-dev X-Developer-Signature: v=1; a=openpgp-sha256; l=3702; i=brauner@kernel.org; h=from:subject:message-id; bh=20rJkgesQhfyVvX+iP+2cn2t9uRQnDiG02PYUBwi/V4=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMWS97jPsktFdvOpVs6nmzzyvU+U6ZXtuXBM8rzljz9wMw 1nV1yaYdJSyMIhxMciKKbI4tJuEyy3nqdhslKkBM4eVCWQIAxenAExkmR4jw4orl8X8M5o+3ma9 GfZdRD43+XLkoesF4WpvMhbuurvzRQEjw6V1dx4JZH/R15uYuWfHNB9+M1aVOLPGyMglXg065jc nMgIA X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 Implement ->proc_read_buf() so procfs copies what is read to userspace after it unpinned the entry, and take the data out of the fifo with kfifo_out() instead of kfifo_to_user(). A reader that passes a bad buffer loses what was taken out for it now, kfifo_to_user() left that in the fifo. The samples can be spliced now too, and a sendfile() from them into a target that fails or takes less than was read drops what was taken out in between, like for the rtas error log. Signed-off-by: Christian Brauner (Amutable) --- samples/kfifo/bytestream-example.c | 9 +++------ samples/kfifo/inttype-example.c | 10 ++++------ samples/kfifo/record-example.c | 9 +++------ 3 files changed, 10 insertions(+), 18 deletions(-) diff --git a/samples/kfifo/bytestream-example.c b/samples/kfifo/bytestream-example.c index 8c58fb46a2bf..214e46a64cc1 100644 --- a/samples/kfifo/bytestream-example.c +++ b/samples/kfifo/bytestream-example.c @@ -125,26 +125,23 @@ static ssize_t fifo_write(struct file *file, char *buf, return copied; } -static ssize_t fifo_read(struct file *file, char __user *buf, +static ssize_t fifo_read(struct file *file, char *buf, size_t count, loff_t *ppos) { - int ret; unsigned int copied; if (mutex_lock_interruptible(&read_access)) return -ERESTARTSYS; - ret = kfifo_to_user(&test, buf, count, &copied); + copied = kfifo_out(&test, buf, count); mutex_unlock(&read_access); - if (ret) - return ret; return copied; } static const struct proc_ops fifo_proc_ops = { - .proc_read = fifo_read, + .proc_read_buf = fifo_read, .proc_write_buf = fifo_write, .proc_lseek = noop_llseek, }; diff --git a/samples/kfifo/inttype-example.c b/samples/kfifo/inttype-example.c index c5d16b815e73..8384d7f8de6c 100644 --- a/samples/kfifo/inttype-example.c +++ b/samples/kfifo/inttype-example.c @@ -119,26 +119,24 @@ static ssize_t fifo_write(struct file *file, char *buf, return copied; } -static ssize_t fifo_read(struct file *file, char __user *buf, +static ssize_t fifo_read(struct file *file, char *buf, size_t count, loff_t *ppos) { - int ret; unsigned int copied; if (mutex_lock_interruptible(&read_access)) return -ERESTARTSYS; - ret = kfifo_to_user(&test, buf, count, &copied); + copied = kfifo_out(&test, (int *)buf, count / sizeof(int)) * + sizeof(int); mutex_unlock(&read_access); - if (ret) - return ret; return copied; } static const struct proc_ops fifo_proc_ops = { - .proc_read = fifo_read, + .proc_read_buf = fifo_read, .proc_write_buf = fifo_write, .proc_lseek = noop_llseek, }; diff --git a/samples/kfifo/record-example.c b/samples/kfifo/record-example.c index dcc749247c64..29d08e90a63d 100644 --- a/samples/kfifo/record-example.c +++ b/samples/kfifo/record-example.c @@ -132,26 +132,23 @@ static ssize_t fifo_write(struct file *file, char *buf, return copied; } -static ssize_t fifo_read(struct file *file, char __user *buf, +static ssize_t fifo_read(struct file *file, char *buf, size_t count, loff_t *ppos) { - int ret; unsigned int copied; if (mutex_lock_interruptible(&read_access)) return -ERESTARTSYS; - ret = kfifo_to_user(&test, buf, count, &copied); + copied = kfifo_out(&test, buf, count); mutex_unlock(&read_access); - if (ret) - return ret; return copied; } static const struct proc_ops fifo_proc_ops = { - .proc_read = fifo_read, + .proc_read_buf = fifo_read, .proc_write_buf = fifo_write, .proc_lseek = noop_llseek, /* kfifo_from_user() cut a record to what its length byte holds */ -- 2.53.0