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([2a07:b241:1004:8300::1000]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49541e9a7bbsm38107655e9.13.2026.07.16.00.44.28 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 16 Jul 2026 00:44:29 -0700 (PDT) Message-ID: <3d71046a-2fab-4eab-8f0d-d97c3a5bab88@suse.com> Date: Thu, 16 Jul 2026 09:44:28 +0200 Precedence: bulk X-Mailing-List: linux-xfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH] libfrog: make cmn_err() emit each message atomically to avoid torn output To: "Darrick J. Wong" Cc: linux-xfs@vger.kernel.org, fstests@vger.kernel.org, cem@kernel.org References: <20260715173114.359368-1-avinesh.kumar@suse.com> <20260715190949.GP7380@frogsfrogsfrogs> Content-Language: en-US From: Avinesh Kumar In-Reply-To: <20260715190949.GP7380@frogsfrogsfrogs> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Hello Darrick, On 7/15/26 9:09 PM, Darrick J. Wong wrote: > On Wed, Jul 15, 2026 at 07:28:21PM +0200, Avinesh Kumar wrote: >> From: Avinesh Kumar >> >> fstests xfs/033 fails sporadically with a spurious blank line in the >> xfs_repair output: >> >> - output mismatch (see /opt/xfstests/results//xfs/033.out.bad) >> --- tests/xfs/033.out 2026-06-24 15:52:51.000000000 -0400 >> +++ /opt/xfstests/results//xfs/033.out.bad 2026-07-14 18:54:46.582495041 -0400 >> @@ -103,6 +103,7 @@ >> Phase 3 - for each AG... >> - scan and clear agi unlinked lists... >> - process known inodes and perform inode discovery... >> + >> bad magic number 0xffff on inode INO >> bad version number 0xffffffff on inode INO >> inode identifier 18446744073709551615 mismatch on inode INO >> >> Root cause is in cmn_err() (libfrog/util.c), which emits a message >> and its newline as two separate writes to unbuffered stderr. >> xfs_repair's threads all share stderr. If one is preempted between the >> two writes, another thread's line lands in between: >> >> (snips from `cat -A 033.raw`) - >> Phase 3 - for each AG...$ >> - scan and clear agi unlinked lists...$ >> - process known inodes and perform inode discovery...$ >> Metadata corruption detected at 0x445dd3, xfs_inode block 0x80/0x4000 - agno = 0$ >> $ >> bad CRC for inode 128$ >> bad magic number 0x0 on inode 128$ >> >> which should be like - >> >> Phase 3 - for each AG...$ >> - scan and clear agi unlinked lists...$ >> - process known inodes and perform inode discovery...$ >> Metadata corruption detected at 0x445dd3, xfs_inode block 0x80/0x4000$ >> - agno = 0$ >> bad CRC for inode 130$ >> bad magic number 0x0 on inode 130$ >> >> _filter_repair() strips the noise line it glued onto but not the lone >> newline, which then fails the golden diff. >> >> Make the two writes atomic. >> >> Signed-off-by: Avinesh Kumar >> --- >> >> Hi, please give feedback if this should be fixed in a different way. >> Thanks! >> >> libfrog/util.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/libfrog/util.c b/libfrog/util.c >> index 5bae5bab..3b6df917 100644 >> --- a/libfrog/util.c >> +++ b/libfrog/util.c >> @@ -116,8 +116,10 @@ cmn_err(int level, char *fmt, ...) >> va_list ap; >> >> va_start(ap, fmt); >> + flockfile(stderr); >> vfprintf(stderr, fmt, ap); >> fputs("\n", stderr); >> + funlockfile(stderr); > > I think do_error() in xfs_repair.c is going to need the same treatment > but otherwise this chunk looks ok to me. > Thanks for the review. I can send a follow up patch for do_error(), or do you want these to go in the same patch? Regards, Avinesh > --D > >> va_end(ap); >> } >> >> -- >> 2.55.0 >> >>