Yes, I was trying to analyze the problem from the perspective of code review/analysis only. Since you like the way starting from the symptoms of the problem, I will try. Thanks, wengang > On May 31, 2024, at 8:52 AM, Darrick J. Wong <djwong@xxxxxxxxxx> wrote: > > On Fri, May 10, 2024 at 05:34:26PM -0700, Wengang Wang wrote: > > You might want to lead off with the origins of this fixpatch: > > "A user with a completely full filesystem experienced an unexpected > shutdown when the filesystem tried to write the superblock during > runtime:" > > <dmesg dump here> > > "When xfs_log_sb writes a superblock to disk, sb_fdblocks is fetched..." > > (or so I'm guessing from the other replies in this thread?) > > ((What was it doing? Adding the ATTR/ATTR2 feature to the filesystem?)) > >> when writting super block to disk (in xfs_log_sb), sb_fdblocks is fetched from >> m_fdblocks without any lock. As m_fdblocks can experience a positive -> negativ > > "negative" > >> -> positive changing when the FS reaches fullness (see xfs_mod_fdblocks) >> So there is a chance that sb_fdblocks is negative, and because sb_fdblocks is >> type of unsigned long long, it reads super big. And sb_fdblocks being bigger >> than sb_dblocks is a problem during log recovery, xfs_validate_sb_write() >> complains. >> >> Fix: >> As sb_fdblocks will be re-calculated during mount when lazysbcount is enabled, >> We just need to make xfs_validate_sb_write() happy -- make sure sb_fdblocks is >> not genative. > > "negative". > > This otherwise looks good to me. > > --D > >> Signed-off-by: Wengang Wang <wen.gang.wang@xxxxxxxxxx> >> --- >> fs/xfs/libxfs/xfs_sb.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/fs/xfs/libxfs/xfs_sb.c b/fs/xfs/libxfs/xfs_sb.c >> index 73a4b895de67..199756970383 100644 >> --- a/fs/xfs/libxfs/xfs_sb.c >> +++ b/fs/xfs/libxfs/xfs_sb.c >> @@ -1037,7 +1037,7 @@ xfs_log_sb( >> mp->m_sb.sb_ifree = min_t(uint64_t, >> percpu_counter_sum(&mp->m_ifree), >> mp->m_sb.sb_icount); >> - mp->m_sb.sb_fdblocks = percpu_counter_sum(&mp->m_fdblocks); >> + mp->m_sb.sb_fdblocks = percpu_counter_sum_positive(&mp->m_fdblocks); >> } >> >> xfs_sb_to_disk(bp->b_addr, &mp->m_sb); >> -- >> 2.39.3 (Apple Git-146) >> >>
