From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from galois.linutronix.de ([2a01:7a0:2:106d:700::1]) by bombadil.infradead.org with esmtps (Exim 4.87 #1 (Red Hat Linux)) id 1cgZZz-0003mp-1s for linux-mtd@lists.infradead.org; Wed, 22 Feb 2017 16:15:49 +0000 Date: Wed, 22 Feb 2017 17:15:21 +0100 From: Sebastian Andrzej Siewior To: Artem Bityutskiy , Richard Weinberger Cc: linux-mtd@lists.infradead.org Subject: [PATCH] ubi/upd: always flush after prepared for an update Message-ID: <20170222161521.4foobhoyelnrad7h@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , In commit 6afaf8a484cb ("UBI: flush wl before clearing update marker") I managed to trigger and fix a similar bug. Now here is another version of which I assumed it wouldn't matter back then but it turns out UBI has a check for it and will error out like this: |ubi0 warning: validate_vid_hdr: inconsistent used_ebs |ubi0 error: validate_vid_hdr: inconsistent VID header at PEB 592 All you need to trigger this is? "ubiupdatevol /dev/ubi0_0 file" + a powercut in the middle of the operation. ubi_start_update() sets the update-marker and puts all EBs on the erase list. After that userland can proceed to write new data while the old EB aren't erased completely. A powercut at this point is usually not that much of a tragedy. UBI won't give read access to the static volume because it has the update marker. It will most likely set the corrupted flag because it misses some EBs. So we are all good. Unless the size of the image that has been written differs from the old image in the magnitude of at least one EB. In that case UBI will find two different values for `used_ebs' and refuse to attach the image with the error message mentioned above. So in order not to get in the situation, the patch will ensure that we wait until everything is removed before it tries to write any data. The alternative would be to detect such a case and remove all EBs at the attached time after we processed the volume-table and see the update-marker set. The patch looks bigger and I doubt it is worth it since usually the write() will wait from time to time for a new EB since usually there not that many spare EB that can be used. Cc: stable@vger.kernel.org Signed-off-by: Sebastian Andrzej Siewior --- drivers/mtd/ubi/upd.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/drivers/mtd/ubi/upd.c b/drivers/mtd/ubi/upd.c index 0134ba32a057..39712560b4c1 100644 --- a/drivers/mtd/ubi/upd.c +++ b/drivers/mtd/ubi/upd.c @@ -148,11 +148,11 @@ int ubi_start_update(struct ubi_device *ubi, struct ubi_volume *vol, return err; } - if (bytes == 0) { - err = ubi_wl_flush(ubi, UBI_ALL, UBI_ALL); - if (err) - return err; + err = ubi_wl_flush(ubi, UBI_ALL, UBI_ALL); + if (err) + return err; + if (bytes == 0) { err = clear_update_marker(ubi, vol, 0); if (err) return err; -- 2.11.0