From 08169a162f97819d3e5b4a342bb9cf5137787154 Mon Sep 17 00:00:00 2001 From: Chen Yu Date: Fri, 14 Apr 2023 20:10:26 +0800 Subject: [PATCH 1/2] PM: hibernate: Turn snapshot_test into global variable There is need to check snapshot_test and open block device in different mode, so as to avoid the race condition. No functional changes intended. Suggested-by: Pavankumar Kondeti Signed-off-by: Chen Yu Signed-off-by: Rafael J. Wysocki --- kernel/power/hibernate.c | 7 ++++++- kernel/power/power.h | 1 + 2 files changed, 7 insertions(+), 1 deletion(-) diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c index 793c55a2becb..aa551b093c3f 100644 --- a/kernel/power/hibernate.c +++ b/kernel/power/hibernate.c @@ -64,6 +64,7 @@ enum { static int hibernation_mode = HIBERNATION_SHUTDOWN; bool freezer_test_done; +bool snapshot_test; static const struct platform_hibernation_ops *hibernation_ops; @@ -716,7 +717,6 @@ static int load_image_and_restore(void) */ int hibernate(void) { - bool snapshot_test = false; unsigned int sleep_flags; int error; @@ -744,6 +744,9 @@ int hibernate(void) if (error) goto Exit; + /* protected by system_transition_mutex */ + snapshot_test = false; + lock_device_hotplug(); /* Allocate memory management structures */ error = create_basic_memory_bitmaps(); @@ -940,6 +943,8 @@ static int software_resume(void) */ mutex_lock_nested(&system_transition_mutex, SINGLE_DEPTH_NESTING); + snapshot_test = false; + if (swsusp_resume_device) goto Check_image; diff --git a/kernel/power/power.h b/kernel/power/power.h index b4f433943209..b83c8d5e188d 100644 --- a/kernel/power/power.h +++ b/kernel/power/power.h @@ -59,6 +59,7 @@ asmlinkage int swsusp_save(void); /* kernel/power/hibernate.c */ extern bool freezer_test_done; +extern bool snapshot_test; extern int hibernation_snapshot(int platform_mode); extern int hibernation_restore(int platform_mode); From 5904de0d735bbb3b4afe9375c5b4f9748f882945 Mon Sep 17 00:00:00 2001 From: Chen Yu Date: Fri, 14 Apr 2023 20:10:42 +0800 Subject: [PATCH 2/2] PM: hibernate: Do not get block device exclusively in test_resume mode The system refused to do a test_resume because it found that the swap device has already been taken by someone else. Specifically, 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 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 Suggested-by: Pavankumar Kondeti Tested-by: Pavankumar Kondeti Tested-by: Wendy Wang Signed-off-by: Chen Yu Signed-off-by: Rafael J. Wysocki --- kernel/power/hibernate.c | 8 ++++++-- kernel/power/swap.c | 8 ++++++-- 2 files changed, 12 insertions(+), 4 deletions(-) diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c index aa551b093c3f..30d1274f03f6 100644 --- a/kernel/power/hibernate.c +++ b/kernel/power/hibernate.c @@ -688,18 +688,22 @@ static int load_image_and_restore(void) { int error; unsigned int flags; + fmode_t mode = FMODE_READ; + + if (snapshot_test) + mode |= FMODE_EXCL; pm_pr_dbg("Loading hibernation image.\n"); lock_device_hotplug(); error = create_basic_memory_bitmaps(); if (error) { - swsusp_close(FMODE_READ | FMODE_EXCL); + swsusp_close(mode); goto Unlock; } error = swsusp_read(&flags); - swsusp_close(FMODE_READ | FMODE_EXCL); + swsusp_close(mode); if (!error) error = hibernation_restore(flags & SF_PLATFORM_MODE); diff --git a/kernel/power/swap.c b/kernel/power/swap.c index 36a1df48280c..92e41ed292ad 100644 --- a/kernel/power/swap.c +++ b/kernel/power/swap.c @@ -1518,9 +1518,13 @@ int swsusp_check(void) { int error; void *holder; + fmode_t mode = FMODE_READ; + + if (snapshot_test) + mode |= FMODE_EXCL; hib_resume_bdev = blkdev_get_by_dev(swsusp_resume_device, - FMODE_READ | FMODE_EXCL, &holder); + mode, &holder); if (!IS_ERR(hib_resume_bdev)) { set_blocksize(hib_resume_bdev, PAGE_SIZE); clear_page(swsusp_header); @@ -1547,7 +1551,7 @@ int swsusp_check(void) put: if (error) - blkdev_put(hib_resume_bdev, FMODE_READ | FMODE_EXCL); + blkdev_put(hib_resume_bdev, mode); else pr_debug("Image signature found, resuming\n"); } else {