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From:   OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: [PATCH] fat: Avoid oops when bdi->io_pages==0
Date:   Sun, 30 Aug 2020 09:59:41 +0900
Message-ID: <87ft85osn6.fsf@mail.parknet.co.jp>
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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@mail.parknet.co.jp>
Cc: <stable@vger.kernel.org>
---
 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);
 
_

-- 
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>