[PATCH] ubi: Fix filesystem corruption on detach when fastmap enabled

[Richard Weinberger]

Heiko, Martin,

Am Dienstag, 16. Januar 2018, 10:11:41 CET schrieb Martin Townsend:
> Ah. Must be the mail client. Sorry about that I'll setup git send-mail
> for v2.  I'll wait to see what Richard has to say in case there is a
> better fix.

Thanks for letting me know!
Indeed, there is a problem. I'm a little astonished that nobody noticed so 
far.
Most likely because while detaching UBI in Linux mostly no Fastmap work is 
scheduled,
and therefore in most cases flush_work(&ubi->fm_work) does nothing.

As you noticed in U-Boot the story is different, you always update the Fastmap 
upon detach.

Martin, can you please explain what corruption you see?
>From reading the code I'd assume that you miss volumes but a full scan would 
recover everything.

For Linux I suggest this fix:

>From 48287459cf8717cffac5aed423937cd7ba4360ab Mon Sep 17 00:00:00 2001
From: Richard Weinberger <richard at nod.at>
Date: Tue, 16 Jan 2018 14:12:46 +0100
Subject: [PATCH] ubi: fastmap: Don't flush fastmap work on detach

At this point UBI volumes have already been free()'ed and fastmap can no
longer access these data structures.

Fixes: 74cdaf24004a ("UBI: Fastmap: Fix memory leaks while closing the WL sub-
system")
Signed-off-by: Richard Weinberger <richard at nod.at>
Cc: stable at vger.kernel.org
---
 drivers/mtd/ubi/fastmap-wl.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/mtd/ubi/fastmap-wl.c b/drivers/mtd/ubi/fastmap-wl.c
index 4f0bd6b4422a..69dd21679a30 100644
--- a/drivers/mtd/ubi/fastmap-wl.c
+++ b/drivers/mtd/ubi/fastmap-wl.c
@@ -362,7 +362,6 @@ static void ubi_fastmap_close(struct ubi_device *ubi)
 {
 	int i;
 
-	flush_work(&ubi->fm_work);
 	return_unused_pool_pebs(ubi, &ubi->fm_pool);
 	return_unused_pool_pebs(ubi, &ubi->fm_wl_pool);
 
-- 
2.13.6

In U-Boot you can do the same.

Thanks,
//richard

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