From: Zhihao Cheng chengzhihao1@huawei.com
hulk inclusion category: bugfix bugzilla: 187685, https://gitee.com/openeuler/kernel/issues/I5VVZX CVE: NA
--------------------------------
UBIFS calculates available space by c->main_bytes - c->lst.total_used (which means non-index lebs' free and dirty space is accounted into total available), then index lebs and four lebs (one for gc_lnum, one for deletions, two for journal heads) are deducted. In following situation, ubifs may get -ENOSPC from make_reservation(): LEB 84: DATAHD free 122880 used 1920 dirty 2176 dark 6144 LEB 110:DELETION free 126976 used 0 dirty 0 dark 6144 (empty) LEB 201:gc_lnum free 126976 used 0 dirty 0 dark 6144 LEB 272:GCHD free 77824 used 47672 dirty 1480 dark 6144 LEB 356:BASEHD free 0 used 39776 dirty 87200 dark 6144 OTHERS: index lebs, zero-available non-index lebs
UBIFS calculates the available bytes is 6888 (How to calculate it: 126976 * 5[remain main bytes] - 1920[used] - 47672[used] - 39776[used] - 126976 * 1[deletions] - 126976 * 1[gc_lnum] - 126976 * 2[journal heads] - 6144 * 5[dark] = 6888) after doing budget, however UBIFS cannot use BASEHD's dirty space(87200), because UBIFS cannot find next BASEHD to reclaim current BASEHD. (c->bi.min_idx_lebs equals to c->lst.idx_lebs, the empty leb won't be found by ubifs_find_free_space(), and dirty index lebs won't be picked as gced lebs. All non-index lebs has dirty space less then c->dead_wm, non-index lebs won't be picked as gced lebs either. So new free lebs won't be produced.). See more details in Link.
To fix it, reserve one leb for each journal head while doing budget.
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216562 Fixes: 1e51764a3c2ac0 ("UBIFS: add new flash file system") Signed-off-by: Zhihao Cheng chengzhihao1@huawei.com Reviewed-by: Zhang Yi yi.zhang@huawei.com Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com --- fs/ubifs/budget.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/fs/ubifs/budget.c b/fs/ubifs/budget.c index bdb79be6dc0e..9cb05ef9b9dd 100644 --- a/fs/ubifs/budget.c +++ b/fs/ubifs/budget.c @@ -212,11 +212,10 @@ long long ubifs_calc_available(const struct ubifs_info *c, int min_idx_lebs) subtract_lebs += 1;
/* - * The GC journal head LEB is not really accessible. And since - * different write types go to different heads, we may count only on - * one head's space. + * Since different write types go to different heads, we should + * reserve one leb for each head. */ - subtract_lebs += c->jhead_cnt - 1; + subtract_lebs += c->jhead_cnt;
/* We also reserve one LEB for deletions, which bypass budgeting */ subtract_lebs += 1;