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Wed, 9 Sep 2026 16:05:46 +0000 (GMT) Message-ID: <951e04d1-1f0e-44bf-9927-71a43dce0a66@linux.ibm.com> Date: Wed, 9 Sep 2026 21:35:43 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 19/22] selftests/coredump: hand the record stream to a sink To: Christian Brauner , linux-fsdevel@vger.kernel.org Cc: Jacob Lalonde , Josef Bacik , Jann Horn , Alexander Viro , Jan Kara , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Omar Sandoval , Jacob Lalonde , Shuah Khan , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linuxppc-dev@lists.ozlabs.org References: <20260820-work-coredump-sparse-v2-0-ba32dd718c51@kernel.org> <20260820-work-coredump-sparse-v2-19-ba32dd718c51@kernel.org> Content-Language: en-US From: R Nageswara Sastry In-Reply-To: <20260820-work-coredump-sparse-v2-19-ba32dd718c51@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-Spam-Info: AW1haW4tMjYwOTA5MDE3OCBTYWx0ZWRfX/nTUjuG+ZIoG TzVqoN/OiDsxQ8DgrkwSwERa4BDUOqqalCE8FiVP94KnJ8kSaK+6aPS3IE81Y4gjHGvAsB90+Gt Xp8pgmTkLEQc80deK0yPnwGQx4ZbqVM= X-Proofpoint-ORIG-GUID: NOkEk_pYqkM7PbxBoTGzdYKiEHVCWHb8 X-Authority-Analysis: v=2.4 cv=NMDlPU6g c=1 sm=1 tr=0 ts=6aa183ea cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=IkcTkHD0fZMA:10 a=VdqzKS8jKosA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=B3ZA3r2n0Fxly1dS26oA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTA5MDE3OCBTYWx0ZWRfXyoOrPrb9R/d3 2Jn3NBmeY+M8qXMNSxuqfqXtHDJZd3IPDZ8QWF3mDWzmlNHrkpeSjJxh+R1dKtFv50kQoQ92m0G 3pbEqH7I8APD4dpKCqf/rTU92Qlr5wXynTQiAtE9iIDGCPcCsWvFaRRhaknd05y19NyN5lxCg6j j+qSdaV09GjDyju4c0UWCnSDjhJVM56+ZBbFdNCLai6o94iTo7PW2EPFLU0PSBrucUdcW6/L9/E iUaYcTigWcearHzSs1m1C1uRonw6zsiy8qeES08Wf0Wwv+SYgx2RYADvsSspq/v1rpSBZeVRrQg 1P0vQguEt0RgJ1ygC9IScGM6aMZIxXMDgAu/Tu+PRQhrx3OU+h7Jz7/zQdtZ6apFTjl6y65pG+k sSHpbNI2lnkTa5XxjZB16G73SDZMviZY9fi9w4bopkjU9+VSyHlaRDEoMKiNQMms8CTvWZTw5db TUuTkZLYdScersFtNKw== X-Proofpoint-GUID: _QmDvftTM8hs8guomGZZhJKwEkm3lgUy X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-09-08_03,2026-09-09_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 spamscore=0 lowpriorityscore=0 clxscore=1015 adultscore=0 impostorscore=0 bulkscore=0 malwarescore=0 priorityscore=1501 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2609090178 X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: E46D51A0006 X-Stat-Signature: sjbgmrrywdii1hhntu6irjkzsw55b5xa X-HE-Tag: 1788969969-983986 X-HE-Meta: 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 2li8JbWv Wq/MYeuk8YQDOC+z0kwUj1tkWKzzRRpSjvqCO76JzL8zCg3Tm4o9RalWUcWgOkihXKVboxVmouex0vu7kwZNAgHZx98jJX5ISYLt+hw1OCxKjRwQJE93idkLj4dgbq0u/yYYhxkAI1XWXxRdqaaDamGsRU7D0rOCJL2AzAdXisIyMUJSpLZyOfsDosse1sT2ev54QAOMTr91PlwATqd2jWJCV43fJY8WrOjHrLE0vuztE4z8Gz2BwonQ+wtvj+nJDFb3qnIhihC2P5ACW/khYAel5JpnR5ylhyCokXFKFXphZ4rwZD6zBtcwDOX9o3bGrGCACMse6o5Ns7wQy5TwY2zERw3oWbAWUACe21F1e+Srluw1fBUgRJXEaAQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 20.08.2026 4:39 AM, Christian Brauner wrote: > Currently recv_coredump_records() parses the record stream and dumps it > into a file. A coredump server may want to process the data it gets. So > split the parsing from the processing. > > No functional changes. > > Signed-off-by: Christian Brauner (Amutable) Tested-by: R Nageswara Sastry System: ppc64le LPAR (IBM POWER), Linux 7.3-rc2 > --- > .../selftests/coredump/coredump_test_helpers.c | 91 +++++++++++++++++----- > 1 file changed, 72 insertions(+), 19 deletions(-) > > diff --git a/tools/testing/selftests/coredump/coredump_test_helpers.c b/tools/testing/selftests/coredump/coredump_test_helpers.c > index 5b2ffe17f7b7..45d76fa0f469 100644 > --- a/tools/testing/selftests/coredump/coredump_test_helpers.c > +++ b/tools/testing/selftests/coredump/coredump_test_helpers.c > @@ -71,9 +71,19 @@ void crashing_child_sparse(size_t size) > *(volatile int *)NULL = 0; > } > > -/* Read @len bytes off the socket, writing them at @offset if @fd_out >= 0. */ > -static ssize_t recv_record_bytes(int fd_coredump, __u64 len, int fd_out, > - off_t offset) > +/* Sink a reassembled record stream is handed to, record by record. */ > +struct coredump_record_sink { > + /* @len bytes of coredump data that belong at @offset. */ > + int (*data)(void *ctx, const void *buf, size_t len, __u64 offset); > + /* @len zero bytes that belong at @offset. */ > + int (*zero)(void *ctx, __u64 offset, __u64 len); > + void *ctx; > +}; > + > +/* Read @len bytes off the socket and hand them to @sink, if there is one. */ > +static ssize_t recv_record_bytes(int fd_coredump, __u64 len, > + const struct coredump_record_sink *sink, > + __u64 offset) > { > ssize_t received = 0; > > @@ -89,11 +99,8 @@ static ssize_t recv_record_bytes(int fd_coredump, __u64 len, int fd_out, > return -1; > } > > - if (fd_out >= 0 && > - pwrite(fd_out, buffer, ret, offset + received) != ret) { > - fprintf(stderr, "%s: pwrite failed: %m\n", __func__); > + if (sink && sink->data(sink->ctx, buffer, ret, offset + received)) > return -1; > - } > > received += ret; > len -= ret; > @@ -102,14 +109,34 @@ static ssize_t recv_record_bytes(int fd_coredump, __u64 len, int fd_out, > return received; > } > > +/* Put the data where the records say it goes and leave the holes alone. */ > +static int file_sink_data(void *ctx, const void *buf, size_t len, __u64 offset) > +{ > + int fd = *(int *)ctx; > + > + if (pwrite(fd, buf, len, offset) != (ssize_t)len) { > + fprintf(stderr, "%s: pwrite failed: %m\n", __func__); > + return -1; > + } > + > + return 0; > +} > + > +static int file_sink_zero(void *ctx, __u64 offset, __u64 len) > +{ > + /* Nothing has to be written for a hole. */ > + return 0; > +} > + > /* > - * Reassemble a record stream. If @fd_peer_pidfd is valid the task behind > - * it is killed once a data record has arrived, so the kernel has to cut > - * the coredump short with the stream already under way. > + * Read a coredump strea and funnel it into @sink. Allow to pass in a > + * @fd_peer_pidfd to simulate coredump truncation by killing it after having > + * received a coredump record. > */ > -ssize_t recv_coredump_records(int fd_coredump, int fd_core_file, > - off_t *coredump_size, bool *truncated, > - int fd_peer_pidfd) > +static ssize_t __recv_coredump_records(int fd_coredump, > + const struct coredump_record_sink *sink, > + off_t *coredump_size, bool *truncated, > + int fd_peer_pidfd) > { > ssize_t received = 0; > off_t size = 0; > @@ -169,7 +196,8 @@ ssize_t recv_coredump_records(int fd_coredump, int fd_core_file, > } > > /* Discard any part of the header we have no use for. */ > - ret = recv_record_bytes(fd_coredump, record.size - known_size, -1, 0); > + ret = recv_record_bytes(fd_coredump, record.size - known_size, > + NULL, 0); > if (ret < 0) > return -1; > received += ret; > @@ -185,10 +213,12 @@ ssize_t recv_coredump_records(int fd_coredump, int fd_core_file, > switch (record.type) { > case COREDUMP_RECORD_ZERO: > /* A hole. It comes with no data and needs none. */ > + if (sink->zero(sink->ctx, record.offset, record.len)) > + return -1; > break; > case COREDUMP_RECORD_DATA: > - ret = recv_record_bytes(fd_coredump, record.len, > - fd_core_file, size); > + ret = recv_record_bytes(fd_coredump, record.len, sink, > + record.offset); > if (ret < 0) > return -1; > received += ret; > @@ -230,6 +260,32 @@ ssize_t recv_coredump_records(int fd_coredump, int fd_core_file, > if (truncated) > *truncated = is_truncated; > > + *coredump_size = size; > + > + fprintf(stderr, "Received %zd bytes for a %s coredump of %llu bytes\n", > + received, is_truncated ? "truncated" : "complete", > + (unsigned long long)size); > + return received; > +} > + > +/* Reassemble a record stream into the coredump it describes. */ > +ssize_t recv_coredump_records(int fd_coredump, int fd_core_file, > + off_t *coredump_size, bool *truncated, > + int fd_peer_pidfd) > +{ > + struct coredump_record_sink sink = { > + .data = file_sink_data, > + .zero = file_sink_zero, > + .ctx = &fd_core_file, > + }; > + ssize_t received; > + off_t size = 0; > + > + received = __recv_coredump_records(fd_coredump, &sink, &size, truncated, > + fd_peer_pidfd); > + if (received < 0) > + return -1; > + > /* > * Nothing is written for a hole, so grow the file to the size the > * records describe in case the coredump ended in one. > @@ -243,9 +299,6 @@ ssize_t recv_coredump_records(int fd_coredump, int fd_core_file, > if (coredump_size) > *coredump_size = size; > > - fprintf(stderr, "Received %zd bytes for a %s coredump of %llu bytes\n", > - received, is_truncated ? "truncated" : "complete", > - (unsigned long long)size); > return received; > } > > -- Thanks and Regards R.Nageswara Sastry