On 16/01/2020 14:12, David Sterba wrote: > On Thu, Jan 16, 2020 at 11:29:20AM +0000, fdmanana@xxxxxxxxxx wrote: >> From: Filipe Manana <fdmanana@xxxxxxxx> >> >> If scrub returns an error we are not copying back the scrub arguments >> structure to user space. This prevents user space to know how much progress >> scrub has done if an error happened - this includes -ECANCELED which is >> returned when users ask for scrub to stop. A particular use case, which is >> used in btrfs-progs, is to resume scrub after it is canceled, in that case >> it relies on checking the progress from the scrub arguments structure and >> then use that progress in a call to resume scrub. >> >> So fix this by always copying the scrub arguments structure to user space, >> overwriting the value returned to user space with -EFAULT only if copying >> the structure failed to let user space know that either that copying did >> not happen, and therefore the structure is stale, or it happened partially >> and the structure is probably not valid and corrupt due to the partial >> copy. >> >> Reported-by: Graham Cobb <g.btrfs@xxxxxxxxxxx> >> Link: https://lore.kernel.org/linux-btrfs/d0a97688-78be-08de-ca7d-bcb4c7fb397e@xxxxxxxxxxx/ >> Fixes: 06fe39ab15a6a4 ("Btrfs: do not overwrite scrub error with fault error in scrub ioctl") >> Signed-off-by: Filipe Manana <fdmanana@xxxxxxxx> > > Added to 5.5-rc queue, thanks. Just to let you know... As promised I have built a Debian Testing kernel (5.3) with this patch applied. My btrfs-scrub-slowly script has now run successfully to completion with 32 cancel/resume cycles (runs for 30 mins then takes 10 min break). If it is useful, feel free to add: Tested-by: Graham Cobb <g.btrfs@xxxxxxxxxxx> Thanks Felipe!
