This change introduces a new flag which can be used with DM_DEV_CREATE to establish the maximum open count allowed for a device. When this flag is set on DM_DEV_CREATE the open_count on dm_ioctl will be intrpreted as an input parameter. This value must be >= 1 or DM_DEV_CREATE will return -ERANGE. When this flag is set when the open count is equal to the max open count any future opens will result in an -EBUSY. Signed-off-by: Brian Geffon <bgeffon@xxxxxxxxxx> --- drivers/md/dm-core.h | 2 ++ drivers/md/dm-ioctl.c | 13 ++++++++++++ drivers/md/dm.c | 39 ++++++++++++++++++++++++++++++++--- drivers/md/dm.h | 7 +++++++ include/uapi/linux/dm-ioctl.h | 9 +++++++- 5 files changed, 66 insertions(+), 4 deletions(-) diff --git a/drivers/md/dm-core.h b/drivers/md/dm-core.h index 55dccdfbcb22..57922a80026e 100644 --- a/drivers/md/dm-core.h +++ b/drivers/md/dm-core.h @@ -57,6 +57,7 @@ struct mapped_device { atomic_t holders; atomic_t open_count; + int max_open_count; struct dm_target *immutable_target; struct target_type *immutable_target_type; @@ -139,6 +140,7 @@ struct mapped_device { #define DMF_SUSPENDED_INTERNALLY 7 #define DMF_POST_SUSPENDING 8 #define DMF_EMULATE_ZONE_APPEND 9 +#define DMF_ENFORCE_OPEN_COUNT 10 void disable_discard(struct mapped_device *md); void disable_write_same(struct mapped_device *md); diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c index 21fe8652b095..8ddf3ab99ef6 100644 --- a/drivers/md/dm-ioctl.c +++ b/drivers/md/dm-ioctl.c @@ -814,6 +814,9 @@ static void __dev_status(struct mapped_device *md, struct dm_ioctl *param) if (dm_test_deferred_remove_flag(md)) param->flags |= DM_DEFERRED_REMOVE; + if (dm_test_enforce_open_count_flag(md)) + param->flags |= DM_ENFORCE_OPEN_COUNT_FLAG; + param->dev = huge_encode_dev(disk_devt(disk)); /* @@ -866,6 +869,16 @@ static int dev_create(struct file *filp, struct dm_ioctl *param, size_t param_si if (r) return r; + if (param->flags & DM_ENFORCE_OPEN_COUNT_FLAG) { + if (param->open_count < 1) { + dm_put(md); + dm_destroy(md); + return -ERANGE; + } + + dm_set_max_open_count(md, param->open_count); + } + r = dm_hash_insert(param->name, *param->uuid ? param->uuid : NULL, md); if (r) { dm_put(md); diff --git a/drivers/md/dm.c b/drivers/md/dm.c index 76d9da49fda7..718bc9fce7c1 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -307,6 +307,7 @@ int dm_deleting_md(struct mapped_device *md) static int dm_blk_open(struct block_device *bdev, fmode_t mode) { struct mapped_device *md; + int ret = -ENXIO; spin_lock(&_minor_lock); @@ -316,16 +317,28 @@ static int dm_blk_open(struct block_device *bdev, fmode_t mode) if (test_bit(DMF_FREEING, &md->flags) || dm_deleting_md(md)) { - md = NULL; goto out; } dm_get(md); + + if (test_bit(DMF_ENFORCE_OPEN_COUNT, &md->flags)) { + /* + * No opens or closes can happen in parallel as both + * paths hold the _minor_lock. + */ + if (atomic_read(&md->open_count) + 1 > md->max_open_count) { + dm_put(md); + ret = -EBUSY; + goto out; + } + } + atomic_inc(&md->open_count); + ret = 0; out: spin_unlock(&_minor_lock); - - return md ? 0 : -ENXIO; + return ret; } static void dm_blk_close(struct gendisk *disk, fmode_t mode) @@ -2219,6 +2232,21 @@ void dm_put(struct mapped_device *md) } EXPORT_SYMBOL_GPL(dm_put); +/* + * dm_set_max_open count can only be called when the device is created, + * it cannot be changed once set. + */ +void dm_set_max_open_count(struct mapped_device *md, int count) +{ + /* + * The max open count cannot be changed + */ + BUG_ON(test_bit(DMF_ENFORCE_OPEN_COUNT, &md->flags)); + + set_bit(DMF_ENFORCE_OPEN_COUNT, &md->flags); + md->max_open_count = count; +} + static bool md_in_flight_bios(struct mapped_device *md) { int cpu; @@ -2795,6 +2823,11 @@ int dm_test_deferred_remove_flag(struct mapped_device *md) return test_bit(DMF_DEFERRED_REMOVE, &md->flags); } +int dm_test_enforce_open_count_flag(struct mapped_device *md) +{ + return test_bit(DMF_ENFORCE_OPEN_COUNT, &md->flags); +} + int dm_suspended(struct dm_target *ti) { return dm_suspended_md(ti->table->md); diff --git a/drivers/md/dm.h b/drivers/md/dm.h index 742d9c80efe1..82f56a066b83 100644 --- a/drivers/md/dm.h +++ b/drivers/md/dm.h @@ -84,6 +84,8 @@ void dm_set_md_type(struct mapped_device *md, enum dm_queue_mode type); enum dm_queue_mode dm_get_md_type(struct mapped_device *md); struct target_type *dm_get_immutable_target_type(struct mapped_device *md); +void dm_set_max_open_count(struct mapped_device *md, int count); + int dm_setup_md_queue(struct mapped_device *md, struct dm_table *t); /* @@ -162,6 +164,11 @@ void dm_internal_resume(struct mapped_device *md); */ int dm_test_deferred_remove_flag(struct mapped_device *md); +/* + * Test if the device is enforcing an open count. + */ +int dm_test_enforce_open_count_flag(struct mapped_device *md); + /* * Try to remove devices marked for deferred removal. */ diff --git a/include/uapi/linux/dm-ioctl.h b/include/uapi/linux/dm-ioctl.h index c12ce30b52df..9da3700c0442 100644 --- a/include/uapi/linux/dm-ioctl.h +++ b/include/uapi/linux/dm-ioctl.h @@ -123,7 +123,7 @@ struct dm_ioctl { * relative to start of this struct */ __u32 target_count; /* in/out */ - __s32 open_count; /* out */ + __s32 open_count; /* in/out, in on DM_DEV_CREATE only */ __u32 flags; /* in/out */ /* @@ -382,4 +382,11 @@ enum { */ #define DM_IMA_MEASUREMENT_FLAG (1 << 19) /* In */ +/* + * If set with DM_DEV_CREATE then the open_count on device creation + * will be set as the maximum concurrent opens allowed on the device. + * Once the open_count has been hit any new opens will result in + * -EBUSY until other users close the device. + */ +#define DM_ENFORCE_OPEN_COUNT_FLAG (1 << 20) /* In/Out */ #endif /* _LINUX_DM_IOCTL_H */ -- 2.35.0.rc0.227.g00780c9af4-goog -- dm-devel mailing list dm-devel@xxxxxxxxxx https://listman.redhat.com/mailman/listinfo/dm-devel