Re: [PATCH] PM: hibernate: Do not get block device exclusively in test_resume mode

Wang, Wendy
2023-04-03T08:06:14Z

On 2023-04-02 at 00:55:40 +0800, Chen Yu wrote:
> The system refused to do a test_resume because it found that the
> swap device has already been taken by someone else. Specificly,
> the swsusp_check()->blkdev_get_by_dev(FMODE_EXCL) is supposed to
> do this check.
>
> Steps to reproduce:
> dd if=/dev/zero of=/swapfile bs=$(cat /proc/meminfo |
> awk '/MemTotal/ {print $2}') count=1024 conv=notrunc
> mkswap /swapfile
> swapon /swapfile
> swap-offset /swapfile
> echo 34816 > /sys/power/resume_offset
> echo test_resume > /sys/power/disk
> echo disk > /sys/power/state
>
> PM: Using 3 thread(s) for compression
> PM: Compressing and saving image data (293150 pages)...
> PM: Image saving progress: 0%
> PM: Image saving progress: 10%
> ata1: SATA link up 1.5 Gbps (SStatus 113 SControl 300)
> ata1.00: configured for UDMA/100
> ata2: SATA link down (SStatus 0 SControl 300)
> ata5: SATA link down (SStatus 0 SControl 300)
> ata6: SATA link down (SStatus 0 SControl 300)
> ata3: SATA link down (SStatus 0 SControl 300)
> ata4: SATA link down (SStatus 0 SControl 300)
> PM: Image saving progress: 20%
> PM: Image saving progress: 30%
> PM: Image saving progress: 40%
> PM: Image saving progress: 50%
> pcieport 0000:00:02.5: pciehp: Slot(0-5): No device found
> PM: Image saving progress: 60%
> PM: Image saving progress: 70%
> PM: Image saving progress: 80%
> PM: Image saving progress: 90%
> PM: Image saving done
> PM: hibernation: Wrote 1172600 kbytes in 2.70 seconds (434.29 MB/s)
> PM: S|
> PM: hibernation: Basic memory bitmaps freed
> PM: Image not found (code -16)
>
> This is because when using the swapfile as the hibernation storage,
> the block device where the swapfile is located has already been mounted
> by the OS distribution(usually been mounted as the rootfs). This is not
> an issue for normal hibernation, because software_resume()->swsusp_check()
> happens before the block device(rootfs) mount. But it is a problem for the
> test_resume mode. Because when test_resume happens, the block device has
> been mounted already.
>
> Thus remove the FMODE_EXCL for test_resume mode. This would not be a
> problem because in test_resume stage, the processes have already been
> frozen, and the race condition described in
> Commit 39fbef4b0f77 ("PM: hibernate: Get block device exclusively in swsusp_check()")
> is unlikely to happen.
>
> Fixes: 39fbef4b0f77 ("PM: hibernate: Get block device exclusively in swsusp_check()")
> Reported-by: Yifan Li <yifan2.li@intel.com>
> Signed-off-by: Chen Yu <yu.c.chen@intel.com>
>
Tested on Intel EMR, PASS.
Tested-by: Wendy Wang <wendy.wang@intel.com>