From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8D13855C1BB; Wed, 9 Sep 2026 16:05:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=148.163.156.1 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788969910; cv=none; b=VI64AjnYffOIP+vo45fAllpF7TJ+oWJqSe9YewdbV3b7fBKyEu0rcS967QtYHZPVfUKJL0zzTHp5bxKrG3AfxoMjXCX1OIRGLXm/mkzoV4GC5XIAqj+10bJeSIW+ZX8/bIl7TTK9zzsET82moO4c8XRZzEJiRBH7GHBlcpaVmUg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788969910; c=relaxed/simple; bh=Kp1TaSMGGS2vTTuFLHm63BDwrzHn+k0JtU2rrEOgEO8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=s+HSXNbBV8lCNW/w/rZGb1fjUXemI7tFJ08Gmcl+Vx/xEestNeYnECMPzkMo3KTe0GcUMsSlpMa7fJanGOrG2IOs5ixOqd6o6egmndP0FD0wT4HXYCpe+MUxbb/R3EFc3dUIhTdG4QPqr0ep4YtdUcv/0I6/UW06NMKsUKvsoi0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.ibm.com; spf=pass smtp.mailfrom=linux.ibm.com; dkim=pass (2048-bit key) header.d=ibm.com header.i=@ibm.com header.b=SrEDIhuR; arc=none smtp.client-ip=148.163.156.1 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.ibm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.ibm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=ibm.com header.i=@ibm.com header.b="SrEDIhuR" Received: from pps.filterd (m0360083.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.18.1.11/8.18.1.11) with ESMTP id 689B1hKQ3817810; Wed, 9 Sep 2026 16:04:38 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=cc :content-transfer-encoding:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to; s=pp1; bh=WYsXXn 8p6OXSPyxX3V4vAYpIZi++bTBOEAll5r8Ihos=; b=SrEDIhuRv60P6FakqpZ6xs 4NhWANrnwj9xKlNkAlDbmVro6FE+aisKwaGOs8xzWOxXhHOFSyZtAENY/HVx0c15 4uCNKcP+O+RjLttfpfxgKTfPPa/WbyGX6+9VLPGto70UQGhg0h8XnR/tu5S4hIQU dSnhUte4HieSsyNmDdMnsLwIaJWXNQFh5cFPJOdm26NHI9JAA49fDDKrga3wNO+/ LeufHryhxdLFGKLyPZI00QuvP/Ga3qr8gHqXEzCRhxY4WOUUcfDrsSlIAObbOlmb W73K8ro7fTzRx9/Hhe6nlj9JiKAA7/039QNamF+/js5b0HPjBK73umvP/TtlSvlQ == Received: from ppma12.dal12v.mail.ibm.com (dc.9e.1632.ip4.static.sl-reverse.com [50.22.158.220]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 4ggbf46yv9-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 09 Sep 2026 16:04:37 +0000 (GMT) Received: from pps.filterd (ppma12.dal12v.mail.ibm.com [127.0.0.1]) by ppma12.dal12v.mail.ibm.com (8.18.1.7/8.18.1.7) with ESMTP id 689FuItd016960; Wed, 9 Sep 2026 16:04:36 GMT Received: from smtprelay01.fra02v.mail.ibm.com ([9.218.2.227]) by ppma12.dal12v.mail.ibm.com (PPS) with ESMTPS id 4ggwdqkayn-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 09 Sep 2026 16:04:36 +0000 (GMT) Received: from smtpav01.fra02v.mail.ibm.com (smtpav01.fra02v.mail.ibm.com [10.20.54.100]) by smtprelay01.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 689G4YdJ30081486 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 9 Sep 2026 16:04:34 GMT Received: from smtpav01.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 9BA4C2004F; Wed, 9 Sep 2026 16:04:34 +0000 (GMT) Received: from smtpav01.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 704FD20040; Wed, 9 Sep 2026 16:04:25 +0000 (GMT) Received: from [9.61.255.18] (unknown [9.61.255.18]) by smtpav01.fra02v.mail.ibm.com (Postfix) with ESMTPS; Wed, 9 Sep 2026 16:04:25 +0000 (GMT) Message-ID: Date: Wed, 9 Sep 2026 21:34:21 +0530 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 16/22] coredump: send the coredump in records if requested 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-v2-16-ba32dd718c51@kernel.org> Content-Language: en-US From: R Nageswara Sastry In-Reply-To: <20260820-work-coredump-sparse-v2-16-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-ORIG-GUID: vqUKkxULiNN02lRPE3LPVFxnTIUD-V-H X-Proofpoint-GUID: GR9VeZ5WIgntuHLjsJhUNTT5DUIG8lhn X-Authority-Analysis: v=2.4 cv=DbEnbPtW c=1 sm=1 tr=0 ts=6aa18396 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=iQ6ETzBq9ecOQQE5vZCe:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=83l6PSosv0iiWiGNQS4A:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTA5MDE3OCBTYWx0ZWRfX/gug1k+Hdzgs WLhsjbgHWIR+pQy8z01L2KXArKRM/qOi3Kej30S91Lo/FRcsFJsL2bSeAe3mUQnCp6RKP9DQbEx ESk4DNHEw3ZZdX4KYC1hhToJn8w7g//Ivf9ZZkYSo1ZD3PZKhOjtAj5NjcFWRBYn8luYFOMP5os rbHHXMZBqqipDhbeOOs7NMXJat1Wc0V/eExphytTna6MGsyi68TsTAxO3VegMcqVWwdi5+26w0j KUv+SO0CzJ5+QpjiLr4AqTobEGscYEH2NPp2lpRbyRW2GeOVIONsKFvwc9r4ygMdqpICVPMmdEN J6pfOHc6IhHa+cBWOv7X6BG5FievuE8VTo66RV2reGdUMP4bCRtKW3+ZMecsKhbXXFkNi4sg7vw uowST6OGbJjAaiNwqsA8sK8QBoxUgsfjtbX3UPiWk72w0TI02xYSQIkqWT72G665xaeUhUkdQhv XP871oVjmZBnONqOf4Q== X-Proofpoint-Spam-Info: AW1haW4tMjYwOTA5MDE3OCBTYWx0ZWRfXwh4gwx0DxMQj 5cfmTkY9+3JahonzEinQeqk2F5qfNRXuediZqi+zGECA2HgWDJEJqMtfpdaXD9ooqhRlscEixOv 1DCVHBA1L+krusIjlcDPO9E4/Z1VFe0= 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 priorityscore=1501 impostorscore=0 adultscore=0 spamscore=0 clxscore=1015 suspectscore=0 bulkscore=0 malwarescore=0 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2609090178 On 20.08.2026 4:39 AM, Christian Brauner wrote: > When the coredump server raises COREDUMP_RECORDS send the coredump in > records. A record consists of a struct coredump_record_header and data. > A header and the bytes it describes go out in one iovec. > > A hole is flushed through __dump_emit() like before. So zeroes still are > sent on the socket as actual data records. Making holes cheap is > COREDUMP_SPARSE's job. > > Signed-off-by: Christian Brauner (Amutable) Tested-by: R Nageswara Sastry System: ppc64le LPAR (IBM POWER), Linux 7.3-rc2 > --- > fs/coredump.c | 150 +++++++++++++++++---- > include/linux/coredump.h | 5 + > .../selftests/coredump/coredump_test_helpers.c | 2 +- > 3 files changed, 127 insertions(+), 30 deletions(-) > > diff --git a/fs/coredump.c b/fs/coredump.c > index 6af3ff0e19a6..b1679930094c 100644 > --- a/fs/coredump.c > +++ b/fs/coredump.c > @@ -51,7 +51,6 @@ > #include > #include > #include > -#include > > #include > #include > @@ -68,6 +67,7 @@ > > static bool dump_vma_snapshot(struct coredump_params *cprm); > static void free_vma_snapshot(struct coredump_params *cprm); > +static void dump_end_record(struct coredump_params *cprm); > > #define CORE_FILE_NOTE_SIZE_DEFAULT (4*1024*1024) > /* Define a reasonable max cap */ > @@ -661,6 +661,8 @@ static int umh_coredump_setup(struct subprocess_info *info, struct cred *new) > return 0; > } > > +static_assert(sizeof(struct coredump_record_header) == COREDUMP_RECORD_HEADER_SIZE_VER0); > + > #ifdef CONFIG_UNIX > /* af_unix halves the send buffer to size a single skb. */ > #define COREDUMP_SOCK_SNDBUF_MIN (3 * PAGE_SIZE) > @@ -803,7 +805,8 @@ static bool coredump_sock_request(struct core_name *cn, struct coredump_params * > struct coredump_req req = { > .size = sizeof(struct coredump_req), > .mask = COREDUMP_KERNEL | COREDUMP_USERSPACE | > - COREDUMP_REJECT | COREDUMP_WAIT, > + COREDUMP_REJECT | COREDUMP_WAIT | > + COREDUMP_RECORDS, > .size_ack = sizeof(struct coredump_ack), > }; > struct coredump_ack ack = {}; > @@ -857,6 +860,19 @@ static bool coredump_sock_request(struct core_name *cn, struct coredump_params * > return false; > } > > + /* Records only describe a coredump the kernel writes. */ > + if ((ack.mask & COREDUMP_RECORDS) && !(ack.mask & COREDUMP_KERNEL)) { > + coredump_sock_mark(cprm->file, COREDUMP_MARK_CONFLICTING); > + return false; > + } > + > + /* Record header scratch; a bvec can't point at the stack. */ > + if (ack.mask & COREDUMP_RECORDS) { > + cprm->record_hdr = kmalloc_obj(*cprm->record_hdr); > + if (!cprm->record_hdr) > + return false; > + } > + > cprm->mask = ack.mask; > return coredump_sock_mark(cprm->file, COREDUMP_MARK_REQACK); > } > @@ -1046,7 +1062,6 @@ static bool coredump_pipe(struct core_name *cn, struct coredump_params *cprm, > static bool coredump_write(struct coredump_params *cprm, > const struct linux_binfmt *binfmt) > { > - > if (dump_interrupted()) { > cprm->state |= COREDUMP_STATE_TRUNCATED; > return true; > @@ -1062,15 +1077,17 @@ static bool coredump_write(struct coredump_params *cprm, > cprm->state |= COREDUMP_STATE_TRUNCATED; > /* > * Ensures that file size is big enough to contain the current > - * file postion. This prevents gdb from complaining about > + * file position. This prevents gdb from complaining about > * a truncated file if the last "write" to the file was > - * dump_skip. > + * dump_skip. A record stream relies on it too: the flush > + * emits the records that cover a trailing hole. > */ > if (cprm->to_skip) { > cprm->to_skip--; > if (!dump_emit(cprm, "", 1)) > cprm->state |= COREDUMP_STATE_TRUNCATED; > } > + dump_end_record(cprm); > file_end_write(cprm->file); > free_vma_snapshot(cprm); > return true; > @@ -1085,6 +1102,7 @@ static void coredump_cleanup(struct core_name *cn, struct coredump_params *cprm) > atomic_dec(&core_pipe_count); > } > kfree(cn->corename); > + kfree(cprm->record_hdr); > coredump_finish(cprm->state); > } > > @@ -1218,26 +1236,74 @@ void vfs_coredump(const kernel_siginfo_t *siginfo) > * do on a core-file: use only these functions to write out all the > * necessary info. > */ > -/* One write, never more than a page. See __dump_emit(). */ > -static bool dump_emit_chunk(struct coredump_params *cprm, const void *addr, > - int nr) > +static bool dump_records(const struct coredump_params *cprm) > +{ > + return cprm->mask & COREDUMP_RECORDS; > +} > + > +/* Describe the next @len bytes of the coredump. Returns the header size. */ > +static size_t dump_record_init(struct coredump_params *cprm, > + enum coredump_record_type type, u64 flags, > + u64 len) > +{ > + if (!dump_records(cprm)) > + return 0; > + > + *cprm->record_hdr = (struct coredump_record_header) { > + .size = sizeof(*cprm->record_hdr), > + .type = type, > + .flags = flags, > + .offset = cprm->pos, > + .len = len, > + }; > + > + return sizeof(*cprm->record_hdr); > +} > + > +/* Write @iter whole or fail. @len is what it advances the coredump by. */ > +static bool dump_write_iter(struct coredump_params *cprm, struct iov_iter *iter, > + size_t len) > { > struct file *file = cprm->file; > + size_t count = iov_iter_count(iter); > loff_t pos = file->f_pos; > ssize_t n; > > - if (dump_interrupted()) > + n = __kernel_write_iter(file, iter, &pos); > + if (n != (ssize_t)count) > return false; > + file->f_pos = pos; > + cprm->written += count; > + cprm->pos += len; > + > + return true; > +} > + > +/* One record, never more than a page. See __dump_emit(). */ > +static bool dump_emit_chunk(struct coredump_params *cprm, const void *addr, > + int nr) > +{ > + struct kvec kvec[2]; > + struct iov_iter iter; > + unsigned int nseg = 0; > + size_t hdrlen; > > - n = __kernel_write(file, addr, nr, &pos); > - if (n != nr) > + if (dump_interrupted()) > return false; > > - file->f_pos = pos; > - cprm->written += n; > - cprm->pos += n; > + hdrlen = dump_record_init(cprm, COREDUMP_RECORD_DATA, 0, nr); > + if (hdrlen) { > + kvec[nseg].iov_base = cprm->record_hdr; > + kvec[nseg].iov_len = hdrlen; > + nseg++; > + } > + kvec[nseg].iov_base = (void *)addr; > + kvec[nseg].iov_len = nr; > + nseg++; > > - return true; > + iov_iter_kvec(&iter, ITER_SOURCE, kvec, nseg, hdrlen + nr); > + > + return dump_write_iter(cprm, &iter, nr); > } > > static bool __dump_emit(struct coredump_params *cprm, const void *addr, int nr) > @@ -1258,6 +1324,34 @@ static bool __dump_emit(struct coredump_params *cprm, const void *addr, int nr) > return true; > } > > +/* Send a record that stands on its own: a header and nothing else. */ > +static bool dump_emit_record(struct coredump_params *cprm, > + enum coredump_record_type type, u64 flags, u64 len) > +{ > + struct kvec kvec; > + struct iov_iter iter; > + size_t hdrlen; > + > + hdrlen = dump_record_init(cprm, type, flags, len); > + if (!hdrlen) > + return false; > + > + kvec.iov_base = cprm->record_hdr; > + kvec.iov_len = hdrlen; > + iov_iter_kvec(&iter, ITER_SOURCE, &kvec, 1, hdrlen); > + > + return dump_write_iter(cprm, &iter, len); > +} > + > +/* Close the record stream. Only a whole coredump gets an end record. */ > +static void dump_end_record(struct coredump_params *cprm) > +{ > + if (cprm->state & COREDUMP_STATE_TRUNCATED) > + return; > + > + dump_emit_record(cprm, COREDUMP_RECORD_END, 0, 0); > +} > + > static bool __dump_skip(struct coredump_params *cprm, size_t nr) > { > static char zeroes[PAGE_SIZE]; > @@ -1318,11 +1412,10 @@ EXPORT_SYMBOL(dump_skip); > #ifdef CONFIG_ELF_CORE > static bool dump_emit_page(struct coredump_params *cprm, struct page *page) > { > - struct bio_vec bvec; > + struct bio_vec bvec[2]; > struct iov_iter iter; > - struct file *file = cprm->file; > - loff_t pos; > - ssize_t n; > + unsigned int nseg = 0; > + size_t hdrlen; > > if (!page) > return false; > @@ -1333,17 +1426,16 @@ static bool dump_emit_page(struct coredump_params *cprm, struct page *page) > return false; > if (dump_interrupted()) > return false; > - pos = file->f_pos; > - bvec_set_page(&bvec, page, PAGE_SIZE, 0); > - iov_iter_bvec(&iter, ITER_SOURCE, &bvec, 1, PAGE_SIZE); > - n = __kernel_write_iter(cprm->file, &iter, &pos); > - if (n != PAGE_SIZE) > - return false; > - file->f_pos = pos; > - cprm->written += PAGE_SIZE; > - cprm->pos += PAGE_SIZE; > > - return true; > + /* Hand the record header to the same write as the page it describes. */ > + hdrlen = dump_record_init(cprm, COREDUMP_RECORD_DATA, 0, PAGE_SIZE); > + if (hdrlen) > + bvec_set_virt(&bvec[nseg++], cprm->record_hdr, hdrlen); > + bvec_set_page(&bvec[nseg++], page, PAGE_SIZE, 0); > + > + iov_iter_bvec(&iter, ITER_SOURCE, bvec, nseg, hdrlen + PAGE_SIZE); > + > + return dump_write_iter(cprm, &iter, PAGE_SIZE); > } > > /* > diff --git a/include/linux/coredump.h b/include/linux/coredump.h > index 709388dd5659..b252bb2843b3 100644 > --- a/include/linux/coredump.h > +++ b/include/linux/coredump.h > @@ -6,6 +6,7 @@ > #include > #include > #include > +#include > #include > > #ifdef CONFIG_COREDUMP > @@ -40,7 +41,11 @@ struct coredump_params { > u64 mask; > /* COREDUMP_STATE_* raised while the coredump is written. */ > enum coredump_state state; > + /* Record header scratch, NULL unless the coredump is a record stream. */ > + struct coredump_record_header *record_hdr; > + /* Bytes handed to the file, record headers included. */ > loff_t written; > + /* Offset in the coredump, record headers excluded. */ > loff_t pos; > loff_t to_skip; > int vma_count; > diff --git a/tools/testing/selftests/coredump/coredump_test_helpers.c b/tools/testing/selftests/coredump/coredump_test_helpers.c > index 570fc2e005c2..1c8658f35735 100644 > --- a/tools/testing/selftests/coredump/coredump_test_helpers.c > +++ b/tools/testing/selftests/coredump/coredump_test_helpers.c > @@ -275,7 +275,7 @@ bool send_coredump_ack(int fd, const struct coredump_req *req, > /* Every option the kernel is expected to advertise in coredump_req->mask. */ > #define TEST_REQ_MASK_ALL \ > (COREDUMP_KERNEL | COREDUMP_USERSPACE | \ > - COREDUMP_REJECT | COREDUMP_WAIT) > + COREDUMP_REJECT | COREDUMP_WAIT | COREDUMP_RECORDS) > > bool check_coredump_req(const struct coredump_req *req) > { > -- Thanks and Regards R.Nageswara Sastry