Jens Axboe <axboe@xxxxxxxxx> writes: > On Sat, Aug 29, 2020 at 7:08 PM OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx> wrote: >> >> On one system, there was bdi->io_pages==0. This seems to be the bug of >> a driver somewhere, and should fix it though. Anyway, it is better to >> avoid the divide-by-zero Oops. >> >> So this check it. >> >> Signed-off-by: OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx> >> Cc: <stable@xxxxxxxxxxxxxxx> >> --- >> fs/fat/fatent.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/fs/fat/fatent.c b/fs/fat/fatent.c >> index f7e3304..98a1c4f 100644 >> --- a/fs/fat/fatent.c 2020-08-30 06:52:47.251564566 +0900 >> +++ b/fs/fat/fatent.c 2020-08-30 06:54:05.838319213 +0900 >> @@ -660,7 +660,7 @@ static void fat_ra_init(struct super_blo >> if (fatent->entry >= ent_limit) >> return; >> >> - if (ra_pages > sb->s_bdi->io_pages) >> + if (sb->s_bdi->io_pages && ra_pages > sb->s_bdi->io_pages) >> ra_pages = rounddown(ra_pages, sb->s_bdi->io_pages); >> reada_blocks = ra_pages << (PAGE_SHIFT - sb->s_blocksize_bits + 1); > > I don't think we should work-around this here. What device is this on? > Something like the below may help. The reported bug is from nvme stack, and the below patch (I submitted same patch to you) fixed the reported case though. But I didn't verify all possible path, so I'd liked to use safer side. If block layer can guarantee io_pages!=0 instead, and can apply to stable branch (5.8+). It would work too. Thanks. > diff --git a/block/blk-core.c b/block/blk-core.c > index d9d632639bd1..10c08ac50697 100644 > --- a/block/blk-core.c > +++ b/block/blk-core.c > @@ -539,6 +539,7 @@ struct request_queue *blk_alloc_queue(int node_id) > goto fail_stats; > > q->backing_dev_info->ra_pages = VM_READAHEAD_PAGES; > + q->backing_dev_info->io_pages = VM_READAHEAD_PAGES; > q->backing_dev_info->capabilities = BDI_CAP_CGROUP_WRITEBACK; > q->node = node_id; -- OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
