Hi I discussed this uevent thing with Zdenek and we concluded that it is sufficient to send just one uevent on resize, not two. So, I made a second patch that fixes the uevent-while-suspended bug. It replaces set_capacity_and_notify with set_capacity (so that no uevent is set at this point) and it detects capacity change in do_resume - and if the capacity was changed, it adds "RESIZE=1" to an uevent that is being sent. Zdenek and Peter, please test it. Mikulas From: Mikulas Patocka <mpatocka@xxxxxxxxxx> Device mapper sends an uevent when the device is suspended, using the function set_capacity_and_notify. However, this causes a race condition with udev. Udev skips scanning dm devices that are suspended. If we send an uevent while we are suspended, udev will be racing with device mapper resume code. If the device mapper resume code wins the race, udev will process the uevent after the device is resumed and it will properly scan the device. However, if udev wins the race, it will receive the uevent, find out that the dm device is suspended and skip scanning the device. This causes bugs such as systemd unmounting the device - see https://bugzilla.redhat.com/show_bug.cgi?id=2158628 This commit fixes this race. We replace the function set_capacity_and_notify with set_capacity, so that the uevent is not sent at this point. In do_resume, we detect if the capacity has changed and we pass a boolean variable need_resize_uevent to dm_kobject_uevent. dm_kobject_uevent adds "RESIZE=1" to the uevent if need_resize_uevent is set. Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx --- drivers/md/dm-ioctl.c | 13 ++++++++++--- drivers/md/dm.c | 27 +++++++++++++-------------- drivers/md/dm.h | 2 +- 3 files changed, 24 insertions(+), 18 deletions(-) Index: linux-2.6/drivers/md/dm-ioctl.c =================================================================== --- linux-2.6.orig/drivers/md/dm-ioctl.c 2023-02-09 15:46:39.000000000 +0100 +++ linux-2.6/drivers/md/dm-ioctl.c 2023-02-09 15:46:39.000000000 +0100 @@ -482,7 +482,7 @@ static struct mapped_device *dm_hash_ren dm_table_event(table); dm_put_live_table(hc->md, srcu_idx); - if (!dm_kobject_uevent(hc->md, KOBJ_CHANGE, param->event_nr)) + if (!dm_kobject_uevent(hc->md, KOBJ_CHANGE, param->event_nr, false)) param->flags |= DM_UEVENT_GENERATED_FLAG; md = hc->md; @@ -995,7 +995,7 @@ static int dev_remove(struct file *filp, dm_ima_measure_on_device_remove(md, false); - if (!dm_kobject_uevent(md, KOBJ_REMOVE, param->event_nr)) + if (!dm_kobject_uevent(md, KOBJ_REMOVE, param->event_nr, false)) param->flags |= DM_UEVENT_GENERATED_FLAG; dm_put(md); @@ -1129,6 +1129,7 @@ static int do_resume(struct dm_ioctl *pa struct hash_cell *hc; struct mapped_device *md; struct dm_table *new_map, *old_map = NULL; + bool need_resize_uevent = false; down_write(&_hash_lock); @@ -1149,6 +1150,8 @@ static int do_resume(struct dm_ioctl *pa /* Do we need to load a new map ? */ if (new_map) { + sector_t old_size, new_size; + /* Suspend if it isn't already suspended */ if (param->flags & DM_SKIP_LOCKFS_FLAG) suspend_flags &= ~DM_SUSPEND_LOCKFS_FLAG; @@ -1157,6 +1160,7 @@ static int do_resume(struct dm_ioctl *pa if (!dm_suspended_md(md)) dm_suspend(md, suspend_flags); + old_size = dm_get_size(md); old_map = dm_swap_table(md, new_map); if (IS_ERR(old_map)) { dm_sync_table(md); @@ -1164,6 +1168,9 @@ static int do_resume(struct dm_ioctl *pa dm_put(md); return PTR_ERR(old_map); } + new_size = dm_get_size(md); + if (old_size && new_size && old_size != new_size) + need_resize_uevent = true; if (dm_table_get_mode(new_map) & FMODE_WRITE) set_disk_ro(dm_disk(md), 0); @@ -1176,7 +1183,7 @@ static int do_resume(struct dm_ioctl *pa if (!r) { dm_ima_measure_on_device_resume(md, new_map ? true : false); - if (!dm_kobject_uevent(md, KOBJ_CHANGE, param->event_nr)) + if (!dm_kobject_uevent(md, KOBJ_CHANGE, param->event_nr, need_resize_uevent)) param->flags |= DM_UEVENT_GENERATED_FLAG; } } Index: linux-2.6/drivers/md/dm.c =================================================================== --- linux-2.6.orig/drivers/md/dm.c 2023-02-09 15:46:39.000000000 +0100 +++ linux-2.6/drivers/md/dm.c 2023-02-09 15:46:39.000000000 +0100 @@ -2172,10 +2172,7 @@ static struct dm_table *__bind(struct ma if (size != dm_get_size(md)) memset(&md->geometry, 0, sizeof(md->geometry)); - if (!get_capacity(md->disk)) - set_capacity(md->disk, size); - else - set_capacity_and_notify(md->disk, size); + set_capacity(md->disk, size); dm_table_event_callback(t, event_callback, md); @@ -2968,23 +2965,25 @@ EXPORT_SYMBOL_GPL(dm_internal_resume_fas * Event notification. *---------------------------------------------------------------*/ int dm_kobject_uevent(struct mapped_device *md, enum kobject_action action, - unsigned cookie) + unsigned cookie, bool need_resize_uevent) { int r; unsigned noio_flag; char udev_cookie[DM_COOKIE_LENGTH]; - char *envp[] = { udev_cookie, NULL }; - - noio_flag = memalloc_noio_save(); - - if (!cookie) - r = kobject_uevent(&disk_to_dev(md->disk)->kobj, action); - else { + char *envp[3] = { NULL, NULL, NULL }; + char **envpp = envp; + if (cookie) { snprintf(udev_cookie, DM_COOKIE_LENGTH, "%s=%u", DM_COOKIE_ENV_VAR_NAME, cookie); - r = kobject_uevent_env(&disk_to_dev(md->disk)->kobj, - action, envp); + *envpp++ = udev_cookie; } + if (need_resize_uevent) { + *envpp++ = "RESIZE=1"; + } + + noio_flag = memalloc_noio_save(); + + r = kobject_uevent_env(&disk_to_dev(md->disk)->kobj, action, envp); memalloc_noio_restore(noio_flag); Index: linux-2.6/drivers/md/dm.h =================================================================== --- linux-2.6.orig/drivers/md/dm.h 2023-02-09 15:46:39.000000000 +0100 +++ linux-2.6/drivers/md/dm.h 2023-02-09 15:46:39.000000000 +0100 @@ -203,7 +203,7 @@ int dm_get_table_device(struct mapped_de void dm_put_table_device(struct mapped_device *md, struct dm_dev *d); int dm_kobject_uevent(struct mapped_device *md, enum kobject_action action, - unsigned cookie); + unsigned cookie, bool need_resize_uevent); void dm_internal_suspend(struct mapped_device *md); void dm_internal_resume(struct mapped_device *md); -- dm-devel mailing list dm-devel@xxxxxxxxxx https://listman.redhat.com/mailman/listinfo/dm-devel
