From: Jonathan E Brassow Allow userspace dm log implementations to register their log device so it is no longer missing from the list of device dependencies. When device mapper targets use a device they normally call dm_get_device which includes it in the device list returned to userspace applications such as LVM through the DM_TABLE_DEPS ioctl. Userspace log devices don't use dm_get_device as userspace opens them so they are missing from the list of dependencies. This patch extends the DM_ULOG_CTR operation to allow userspace to respond with the name of the log device (if appropriate) to be registered via 'dm_get_device'. DM_ULOG_REQUEST_VERSION is incremented. This is backwards compatible. If the kernel and userspace log server have both been updated, the new information will be passed down to the kernel and the device will be registered. If the kernel is new, but the log server is old, the log server will not pass down any device information and the kernel will simply bypass the device registration as before. If the kernel is old but the log server is new, the log server will see the old version number and not pass the device info. Signed-off-by: Jonathan Brassow --- FIXME - Fix null termination code - strlen overrun - agk drivers/md/dm-log-userspace-base.c | 39 ++++++++++++++++++++++++++++++++++--- include/linux/dm-log-userspace.h | 18 ++++++++++++----- 2 files changed, 49 insertions(+), 8 deletions(-) Index: linux/drivers/md/dm-log-userspace-base.c =================================================================== --- linux.orig/drivers/md/dm-log-userspace-base.c +++ linux/drivers/md/dm-log-userspace-base.c @@ -30,6 +30,7 @@ struct flush_entry { struct log_c { struct dm_target *ti; + struct dm_dev *log_dev; uint32_t region_size; region_t region_count; uint64_t luid; @@ -161,13 +162,15 @@ static int userspace_ctr(struct dm_dirty struct log_c *lc = NULL; uint64_t rdata; size_t rdata_size = sizeof(rdata); + char *devices_rdata = NULL; + size_t devices_rdata_size = DM_NAME_LEN; if (argc < 3) { DMWARN("Too few arguments to userspace dirty log"); return -EINVAL; } - lc = kmalloc(sizeof(*lc), GFP_KERNEL); + lc = kzalloc(sizeof(*lc), GFP_KERNEL); if (!lc) { DMWARN("Unable to allocate userspace log context."); return -ENOMEM; @@ -195,9 +198,19 @@ static int userspace_ctr(struct dm_dirty return str_size; } - /* Send table string */ + devices_rdata = kzalloc(devices_rdata_size, GFP_KERNEL); + if (!devices_rdata) { + DMERR("Failed to allocate memory for device information"); + r = -ENOMEM; + goto out; + } + + /* + * Send table string and get back any required devices + */ r = dm_consult_userspace(lc->uuid, lc->luid, DM_ULOG_CTR, - ctr_str, str_size, NULL, NULL); + ctr_str, str_size, + devices_rdata, &devices_rdata_size); if (r < 0) { if (r == -ESRCH) @@ -220,7 +233,24 @@ static int userspace_ctr(struct dm_dirty lc->region_size = (uint32_t)rdata; lc->region_count = dm_sector_div_up(ti->len, lc->region_size); + if (devices_rdata_size) { + /* Strings must be properly NULL terminated */ + devices_rdata[DM_NAME_LEN - 1] = '\0'; + if ((strlen(devices_rdata) + 1) != devices_rdata_size) { + DMERR("CTR device return string not properly terminated: Auto-terminating"); + if (devices_rdata_size < DM_NAME_LEN) + /* Add trailing NULL if enough space */ + devices_rdata[devices_rdata_size] = '\0'; + } + r = dm_get_device(ti, devices_rdata, + dm_table_get_mode(ti->table), &lc->log_dev); + if (r) + DMERR("Failed to register %s with device-mapper", + devices_rdata); + } out: + kfree(devices_rdata); + if (r) { kfree(lc); kfree(ctr_str); @@ -241,6 +271,9 @@ static void userspace_dtr(struct dm_dirt NULL, 0, NULL, NULL); + if (lc->log_dev) + dm_put_device(lc->ti, lc->log_dev); + kfree(lc->usr_argv_str); kfree(lc); Index: linux/include/linux/dm-log-userspace.h =================================================================== --- linux.orig/include/linux/dm-log-userspace.h +++ linux/include/linux/dm-log-userspace.h @@ -52,15 +52,20 @@ * Payload-to-userspace: * A single string containing all the argv arguments separated by ' 's * Payload-to-kernel: - * None. ('data_size' in the dm_ulog_request struct should be 0.) + * The name of the device that is used as the backing store for the log + * data. 'dm_get_device' will be called on this device. ('dm_put_device' + * will be called on this device automatically after calling DM_ULOG_DTR.) + * If there is no device needed for log data, 'data_size' in the + * dm_ulog_request struct should be 0. * * The UUID contained in the dm_ulog_request structure is the reference that * will be used by all request types to a specific log. The constructor must - * record this assotiation with instance created. + * record this assotiation with the instance created. * * When the request has been processed, user-space must return the - * dm_ulog_request to the kernel - setting the 'error' field and - * 'data_size' appropriately. + * dm_ulog_request to the kernel - setting the 'error' field, filling the + * data field with the log device if necessary, and setting 'data_size' + * appropriately. */ #define DM_ULOG_CTR 1 @@ -377,8 +382,11 @@ * dm_ulog_request or a change in the way requests are * issued/handled. Changes are outlined here: * version 1: Initial implementation + * version 2: DM_ULOG_CTR allowed to return a string containing a + * device name that is to be registered with DM via + * 'dm_get_device'. */ -#define DM_ULOG_REQUEST_VERSION 1 +#define DM_ULOG_REQUEST_VERSION 2 struct dm_ulog_request { /*