From fd7c092e711ebab55b2688d3859d95dfd0301f73 Mon Sep 17 00:00:00 2001 From: Mikulas Patocka Date: Fri, 1 Mar 2013 22:45:44 +0000 Subject: dm: fix truncated status strings Avoid returning a truncated table or status string instead of setting the DM_BUFFER_FULL_FLAG when the last target of a table fills the buffer. When processing a table or status request, the function retrieve_status calls ti->type->status. If ti->type->status returns non-zero, retrieve_status assumes that the buffer overflowed and sets DM_BUFFER_FULL_FLAG. However, targets don't return non-zero values from their status method on overflow. Most targets returns always zero. If a buffer overflow happens in a target that is not the last in the table, it gets noticed during the next iteration of the loop in retrieve_status; but if a buffer overflow happens in the last target, it goes unnoticed and erroneously truncated data is returned. In the current code, the targets behave in the following way: * dm-crypt returns -ENOMEM if there is not enough space to store the key, but it returns 0 on all other overflows. * dm-thin returns errors from the status method if a disk error happened. This is incorrect because retrieve_status doesn't check the error code, it assumes that all non-zero values mean buffer overflow. * all the other targets always return 0. This patch changes the ti->type->status function to return void (because most targets don't use the return code). Overflow is detected in retrieve_status: if the status method fills up the remaining space completely, it is assumed that buffer overflow happened. Cc: stable@vger.kernel.org Signed-off-by: Mikulas Patocka Signed-off-by: Alasdair G Kergon --- include/linux/device-mapper.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'include/linux') diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h index bf6afa2fc432..a5cda3ea6b88 100644 --- a/include/linux/device-mapper.h +++ b/include/linux/device-mapper.h @@ -68,8 +68,8 @@ typedef void (*dm_postsuspend_fn) (struct dm_target *ti); typedef int (*dm_preresume_fn) (struct dm_target *ti); typedef void (*dm_resume_fn) (struct dm_target *ti); -typedef int (*dm_status_fn) (struct dm_target *ti, status_type_t status_type, - unsigned status_flags, char *result, unsigned maxlen); +typedef void (*dm_status_fn) (struct dm_target *ti, status_type_t status_type, + unsigned status_flags, char *result, unsigned maxlen); typedef int (*dm_message_fn) (struct dm_target *ti, unsigned argc, char **argv); -- cgit v1.2.3 From 55a62eef8d1b50ceff3b7bf46851103bdcc7e5b0 Mon Sep 17 00:00:00 2001 From: Alasdair G Kergon Date: Fri, 1 Mar 2013 22:45:47 +0000 Subject: dm: rename request variables to bios Use 'bio' in the name of variables and functions that deal with bios rather than 'request' to avoid confusion with the normal block layer use of 'request'. No functional changes. Signed-off-by: Alasdair G Kergon --- include/linux/device-mapper.h | 30 +++++++++++++++--------------- 1 file changed, 15 insertions(+), 15 deletions(-) (limited to 'include/linux') diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h index a5cda3ea6b88..d5f984b07466 100644 --- a/include/linux/device-mapper.h +++ b/include/linux/device-mapper.h @@ -187,26 +187,26 @@ struct dm_target { uint32_t max_io_len; /* - * A number of zero-length barrier requests that will be submitted + * A number of zero-length barrier bios that will be submitted * to the target for the purpose of flushing cache. * - * The request number can be accessed with dm_bio_get_target_request_nr. - * It is a responsibility of the target driver to remap these requests + * The bio number can be accessed with dm_bio_get_target_bio_nr. + * It is a responsibility of the target driver to remap these bios * to the real underlying devices. */ - unsigned num_flush_requests; + unsigned num_flush_bios; /* - * The number of discard requests that will be submitted to the target. - * The request number can be accessed with dm_bio_get_target_request_nr. + * The number of discard bios that will be submitted to the target. + * The bio number can be accessed with dm_bio_get_target_bio_nr. */ - unsigned num_discard_requests; + unsigned num_discard_bios; /* - * The number of WRITE SAME requests that will be submitted to the target. - * The request number can be accessed with dm_bio_get_target_request_nr. + * The number of WRITE SAME bios that will be submitted to the target. + * The bio number can be accessed with dm_bio_get_target_bio_nr. */ - unsigned num_write_same_requests; + unsigned num_write_same_bios; /* * The minimum number of extra bytes allocated in each bio for the @@ -233,10 +233,10 @@ struct dm_target { bool discards_supported:1; /* - * Set if the target required discard request to be split + * Set if the target required discard bios to be split * on max_io_len boundary. */ - bool split_discard_requests:1; + bool split_discard_bios:1; /* * Set if this target does not return zeroes on discarded blocks. @@ -261,7 +261,7 @@ struct dm_target_io { struct dm_io *io; struct dm_target *ti; union map_info info; - unsigned target_request_nr; + unsigned target_bio_nr; struct bio clone; }; @@ -275,9 +275,9 @@ static inline struct bio *dm_bio_from_per_bio_data(void *data, size_t data_size) return (struct bio *)((char *)data + data_size + offsetof(struct dm_target_io, clone)); } -static inline unsigned dm_bio_get_target_request_nr(const struct bio *bio) +static inline unsigned dm_bio_get_target_bio_nr(const struct bio *bio) { - return container_of(bio, struct dm_target_io, clone)->target_request_nr; + return container_of(bio, struct dm_target_io, clone)->target_bio_nr; } int dm_register_target(struct target_type *t); -- cgit v1.2.3 From df5d2e9089c7d5b8c46f767e4278610ea3e815b9 Mon Sep 17 00:00:00 2001 From: Mikulas Patocka Date: Fri, 1 Mar 2013 22:45:49 +0000 Subject: dm kcopyd: introduce configurable throttling This patch allows the administrator to reduce the rate at which kcopyd issues I/O. Each module that uses kcopyd acquires a throttle parameter that can be set in /sys/module/*/parameters. We maintain a history of kcopyd usage by each module in the variables io_period and total_period in struct dm_kcopyd_throttle. The actual kcopyd activity is calculated as a percentage of time equal to "(100 * io_period / total_period)". This is compared with the user-defined throttle percentage threshold and if it is exceeded, we sleep. Signed-off-by: Mikulas Patocka Signed-off-by: Alasdair G Kergon --- include/linux/dm-kcopyd.h | 25 ++++++++++++++++++++++++- 1 file changed, 24 insertions(+), 1 deletion(-) (limited to 'include/linux') diff --git a/include/linux/dm-kcopyd.h b/include/linux/dm-kcopyd.h index 47d9d376e4e7..f486d636b82e 100644 --- a/include/linux/dm-kcopyd.h +++ b/include/linux/dm-kcopyd.h @@ -21,11 +21,34 @@ #define DM_KCOPYD_IGNORE_ERROR 1 +struct dm_kcopyd_throttle { + unsigned throttle; + unsigned num_io_jobs; + unsigned io_period; + unsigned total_period; + unsigned last_jiffies; +}; + +/* + * kcopyd clients that want to support throttling must pass an initialised + * dm_kcopyd_throttle struct into dm_kcopyd_client_create(). + * Two or more clients may share the same instance of this struct between + * them if they wish to be throttled as a group. + * + * This macro also creates a corresponding module parameter to configure + * the amount of throttling. + */ +#define DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(name, description) \ +static struct dm_kcopyd_throttle dm_kcopyd_throttle = { 100, 0, 0, 0, 0 }; \ +module_param_named(name, dm_kcopyd_throttle.throttle, uint, 0644); \ +MODULE_PARM_DESC(name, description) + /* * To use kcopyd you must first create a dm_kcopyd_client object. + * throttle can be NULL if you don't want any throttling. */ struct dm_kcopyd_client; -struct dm_kcopyd_client *dm_kcopyd_client_create(void); +struct dm_kcopyd_client *dm_kcopyd_client_create(struct dm_kcopyd_throttle *throttle); void dm_kcopyd_client_destroy(struct dm_kcopyd_client *kc); /* -- cgit v1.2.3 From b0d8ed4d96a26ef3ac54a4aa8911c9413070662e Mon Sep 17 00:00:00 2001 From: Alasdair G Kergon Date: Fri, 1 Mar 2013 22:45:49 +0000 Subject: dm: add target num_write_bios fn Add a num_write_bios function to struct target. If an instance of a target sets this, it will be queried before the target's mapping function is called on a write bio, and the response controls the number of copies of the write bio that the target will receive. This provides a convenient way for a target to send the same data to more than one device. The new cache target uses this in writethrough mode, to send the data both to the cache and the backing device. Signed-off-by: Alasdair G Kergon --- include/linux/device-mapper.h | 15 +++++++++++++++ 1 file changed, 15 insertions(+) (limited to 'include/linux') diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h index d5f984b07466..1e483fa7afb4 100644 --- a/include/linux/device-mapper.h +++ b/include/linux/device-mapper.h @@ -175,6 +175,14 @@ struct target_type { #define DM_TARGET_IMMUTABLE 0x00000004 #define dm_target_is_immutable(type) ((type)->features & DM_TARGET_IMMUTABLE) +/* + * Some targets need to be sent the same WRITE bio severals times so + * that they can send copies of it to different devices. This function + * examines any supplied bio and returns the number of copies of it the + * target requires. + */ +typedef unsigned (*dm_num_write_bios_fn) (struct dm_target *ti, struct bio *bio); + struct dm_target { struct dm_table *table; struct target_type *type; @@ -214,6 +222,13 @@ struct dm_target { */ unsigned per_bio_data_size; + /* + * If defined, this function is called to find out how many + * duplicate bios should be sent to the target when writing + * data. + */ + dm_num_write_bios_fn num_write_bios; + /* target specific data */ void *private; -- cgit v1.2.3