Re: [PATCH v2] libfrog: make cmn_err() emit each message atomically to avoid torn output
Carlos Maiolino <[email protected]>
| Newsgroups | org.kernel.vger.linux-xfs,org.kernel.vger.fstests |
|---|---|
| Message-ID | <[email protected]> |
On Thu, Jul 16, 2026 at 09:45:49PM +0200, Avinesh Kumar wrote: > From: Avinesh Kumar <[email protected]> > Adding Andrey to the thread as he's maintaining xfsprogs. > 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. > > do_error() in xfs_repair.c also has same issue, fix that too. > > Signed-off-by: Avinesh Kumar <[email protected]> > --- > v2: fix the do_error() in xfs_repair.c too. > > libfrog/util.c | 2 ++ > repair/xfs_repair.c | 2 ++ > 2 files changed, 4 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); > va_end(ap); > } > > diff --git a/repair/xfs_repair.c b/repair/xfs_repair.c > index 6b97a806..dd758ebc 100644 > --- a/repair/xfs_repair.c > +++ b/repair/xfs_repair.c > @@ -458,10 +458,12 @@ do_error(char const *msg, ...) > { > va_list args; > > + flockfile(stderr); > fprintf(stderr, _("\nfatal error -- ")); > > va_start(args, msg); > vfprintf(stderr, msg, args); > + funlockfile(stderr); > if (dumpcore) > abort(); > exit(1); > -- > 2.55.0 > >