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ffs: wait for trims earlier during unmount to avoid panic

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All softdep processing is supposed to be completed by
softdep_flushfiles() and no more deps are supposed to be created after
that, but if a pending trim completes after softdep_flushfiles() and
before softdep_unmount() then the blkfree that is performed by
ffs_blkfree_trim_task() will create a dep when none should exist, and
if softdep_unmount() is called before that dep is freed then the
kernel will panic.  Prevent this by waiting for trims to complete
earlier in the unmount process, in ffs_flushfiles(), so that any deps
will be freed and any modified CG buffers will be flushed by the final
fsync of the devvp in ffs_flushfiles() as intended.

Reviewed by:	mckusick, kib
Sponsored by:	Netflix
Differential Revision:	https://reviews.freebsd.org/D34806
This commit is contained in:
Chuck Silvers 2022-04-08 10:19:40 -07:00
parent aa597d4049
commit 3dc5f8e19d
1 changed files with 15 additions and 3 deletions
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18
sys/ufs/ffs/ffs_vfsops.c
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@ -1423,9 +1423,7 @@ ffs_unmount(mp, mntflags)
if (susp)
vfs_write_resume(mp, VR_START_WRITE);
if (ump->um_trim_tq != NULL) {
while (ump->um_trim_inflight != 0)
pause("ufsutr", hz);
taskqueue_drain_all(ump->um_trim_tq);
MPASS(ump->um_trim_inflight == 0);
taskqueue_free(ump->um_trim_tq);
free (ump->um_trimhash, M_TRIM);
}
@ -1539,6 +1537,20 @@ ffs_flushfiles(mp, flags, td)
if (qerror == 0 && (error = vflush(mp, 0, flags, td)) != 0)
return (error);
/*
* If this is a forcible unmount and there were any files that
* were unlinked but still open, then vflush() will have
* truncated and freed those files, which might have started
* some trim work. Wait here for any trims to complete
* and process the blkfrees which follow the trims.
* This may create more dirty devvp buffers and softdep deps.
*/
if (ump->um_trim_tq != NULL) {
while (ump->um_trim_inflight != 0)
pause("ufsutr", hz);
taskqueue_drain_all(ump->um_trim_tq);
}
/*
* Flush filesystem metadata.
*/