#include <linux/task_io_accounting_ops.h>
#include <linux/fault-inject.h>
#include <linux/list_sort.h>
+#include <linux/delay.h>
#define CREATE_TRACE_POINTS
#include <trace/events/block.h>
EXPORT_TRACEPOINT_SYMBOL_GPL(block_rq_remap);
EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_complete);
-static int __make_request(struct request_queue *q, struct bio *bio);
-
/*
* For the allocated request tables
*/
}
EXPORT_SYMBOL(blk_put_queue);
-/*
- * Note: If a driver supplied the queue lock, it is disconnected
- * by this function. The actual state of the lock doesn't matter
- * here as the request_queue isn't accessible after this point
- * (QUEUE_FLAG_DEAD is set) and no other requests will be queued.
+/**
+ * blk_drain_queue - drain requests from request_queue
+ * @q: queue to drain
+ * @drain_all: whether to drain all requests or only the ones w/ ELVPRIV
+ *
+ * Drain requests from @q. If @drain_all is set, all requests are drained.
+ * If not, only ELVPRIV requests are drained. The caller is responsible
+ * for ensuring that no new requests which need to be drained are queued.
+ */
+void blk_drain_queue(struct request_queue *q, bool drain_all)
+{
+ while (true) {
+ int nr_rqs;
+
+ spin_lock_irq(q->queue_lock);
+
+ elv_drain_elevator(q);
+ if (drain_all)
+ blk_throtl_drain(q);
+
+ /*
+ * This function might be called on a queue which failed
+ * driver init after queue creation. Some drivers
+ * (e.g. fd) get unhappy in such cases. Kick queue iff
+ * dispatch queue has something on it.
+ */
+ if (!list_empty(&q->queue_head))
+ __blk_run_queue(q);
+
+ if (drain_all)
+ nr_rqs = q->rq.count[0] + q->rq.count[1];
+ else
+ nr_rqs = q->rq.elvpriv;
+
+ spin_unlock_irq(q->queue_lock);
+
+ if (!nr_rqs)
+ break;
+ msleep(10);
+ }
+}
+
+/**
+ * blk_cleanup_queue - shutdown a request queue
+ * @q: request queue to shutdown
+ *
+ * Mark @q DEAD, drain all pending requests, destroy and put it. All
+ * future requests will be failed immediately with -ENODEV.
*/
void blk_cleanup_queue(struct request_queue *q)
{
- /*
- * We know we have process context here, so we can be a little
- * cautious and ensure that pending block actions on this device
- * are done before moving on. Going into this function, we should
- * not have processes doing IO to this device.
- */
- blk_sync_queue(q);
+ spinlock_t *lock = q->queue_lock;
- del_timer_sync(&q->backing_dev_info.laptop_mode_wb_timer);
+ /* mark @q DEAD, no new request or merges will be allowed afterwards */
mutex_lock(&q->sysfs_lock);
queue_flag_set_unlocked(QUEUE_FLAG_DEAD, q);
- mutex_unlock(&q->sysfs_lock);
+
+ spin_lock_irq(lock);
+ queue_flag_set(QUEUE_FLAG_NOMERGES, q);
+ queue_flag_set(QUEUE_FLAG_NOXMERGES, q);
+ queue_flag_set(QUEUE_FLAG_DEAD, q);
if (q->queue_lock != &q->__queue_lock)
q->queue_lock = &q->__queue_lock;
+ spin_unlock_irq(lock);
+ mutex_unlock(&q->sysfs_lock);
+
+ /*
+ * Drain all requests queued before DEAD marking. The caller might
+ * be trying to tear down @q before its elevator is initialized, in
+ * which case we don't want to call into draining.
+ */
+ if (q->elevator)
+ blk_drain_queue(q, true);
+
+ /* @q won't process any more request, flush async actions */
+ del_timer_sync(&q->backing_dev_info.laptop_mode_wb_timer);
+ blk_sync_queue(q);
+
+ /* @q is and will stay empty, shutdown and put */
blk_put_queue(q);
}
EXPORT_SYMBOL(blk_cleanup_queue);
q->backing_dev_info.state = 0;
q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY;
q->backing_dev_info.name = "block";
+ q->node = node_id;
err = bdi_init(&q->backing_dev_info);
if (err) {
if (!uninit_q)
return NULL;
- q = blk_init_allocated_queue_node(uninit_q, rfn, lock, node_id);
+ q = blk_init_allocated_queue(uninit_q, rfn, lock);
if (!q)
blk_cleanup_queue(uninit_q);
struct request_queue *
blk_init_allocated_queue(struct request_queue *q, request_fn_proc *rfn,
spinlock_t *lock)
-{
- return blk_init_allocated_queue_node(q, rfn, lock, -1);
-}
-EXPORT_SYMBOL(blk_init_allocated_queue);
-
-struct request_queue *
-blk_init_allocated_queue_node(struct request_queue *q, request_fn_proc *rfn,
- spinlock_t *lock, int node_id)
{
if (!q)
return NULL;
- q->node = node_id;
if (blk_init_free_list(q))
return NULL;
/*
* This also sets hw/phys segments, boundary and size
*/
- blk_queue_make_request(q, __make_request);
+ blk_queue_make_request(q, blk_queue_bio);
q->sg_reserved_size = INT_MAX;
return NULL;
}
-EXPORT_SYMBOL(blk_init_allocated_queue_node);
+EXPORT_SYMBOL(blk_init_allocated_queue);
int blk_get_queue(struct request_queue *q)
{
}
static struct request *
-blk_alloc_request(struct request_queue *q, int flags, int priv, gfp_t gfp_mask)
+blk_alloc_request(struct request_queue *q, unsigned int flags, gfp_t gfp_mask)
{
struct request *rq = mempool_alloc(q->rq.rq_pool, gfp_mask);
rq->cmd_flags = flags | REQ_ALLOCED;
- if (priv) {
- if (unlikely(elv_set_request(q, rq, gfp_mask))) {
- mempool_free(rq, q->rq.rq_pool);
- return NULL;
- }
- rq->cmd_flags |= REQ_ELVPRIV;
+ if ((flags & REQ_ELVPRIV) &&
+ unlikely(elv_set_request(q, rq, gfp_mask))) {
+ mempool_free(rq, q->rq.rq_pool);
+ return NULL;
}
return rq;
* A request has just been released. Account for it, update the full and
* congestion status, wake up any waiters. Called under q->queue_lock.
*/
-static void freed_request(struct request_queue *q, int sync, int priv)
+static void freed_request(struct request_queue *q, unsigned int flags)
{
struct request_list *rl = &q->rq;
+ int sync = rw_is_sync(flags);
rl->count[sync]--;
- if (priv)
+ if (flags & REQ_ELVPRIV)
rl->elvpriv--;
__freed_request(q, sync);
return true;
}
-/*
- * Get a free request, queue_lock must be held.
- * Returns NULL on failure, with queue_lock held.
- * Returns !NULL on success, with queue_lock *not held*.
+/**
+ * get_request - get a free request
+ * @q: request_queue to allocate request from
+ * @rw_flags: RW and SYNC flags
+ * @bio: bio to allocate request for (can be %NULL)
+ * @gfp_mask: allocation mask
+ *
+ * Get a free request from @q. This function may fail under memory
+ * pressure or if @q is dead.
+ *
+ * Must be callled with @q->queue_lock held and,
+ * Returns %NULL on failure, with @q->queue_lock held.
+ * Returns !%NULL on success, with @q->queue_lock *not held*.
*/
static struct request *get_request(struct request_queue *q, int rw_flags,
struct bio *bio, gfp_t gfp_mask)
struct request_list *rl = &q->rq;
struct io_context *ioc = NULL;
const bool is_sync = rw_is_sync(rw_flags) != 0;
- int may_queue, priv = 0;
+ int may_queue;
+
+ if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags)))
+ return NULL;
may_queue = elv_may_queue(q, rw_flags);
if (may_queue == ELV_MQUEUE_NO)
rl->count[is_sync]++;
rl->starved[is_sync] = 0;
- if (blk_rq_should_init_elevator(bio)) {
- priv = !test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
- if (priv)
- rl->elvpriv++;
+ if (blk_rq_should_init_elevator(bio) &&
+ !test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags)) {
+ rw_flags |= REQ_ELVPRIV;
+ rl->elvpriv++;
}
if (blk_queue_io_stat(q))
rw_flags |= REQ_IO_STAT;
spin_unlock_irq(q->queue_lock);
- rq = blk_alloc_request(q, rw_flags, priv, gfp_mask);
+ rq = blk_alloc_request(q, rw_flags, gfp_mask);
if (unlikely(!rq)) {
/*
* Allocation failed presumably due to memory. Undo anything
* wait queue, but this is pretty rare.
*/
spin_lock_irq(q->queue_lock);
- freed_request(q, is_sync, priv);
+ freed_request(q, rw_flags);
/*
* in the very unlikely event that allocation failed and no
return rq;
}
-/*
- * No available requests for this queue, wait for some requests to become
- * available.
+/**
+ * get_request_wait - get a free request with retry
+ * @q: request_queue to allocate request from
+ * @rw_flags: RW and SYNC flags
+ * @bio: bio to allocate request for (can be %NULL)
+ *
+ * Get a free request from @q. This function keeps retrying under memory
+ * pressure and fails iff @q is dead.
*
- * Called with q->queue_lock held, and returns with it unlocked.
+ * Must be callled with @q->queue_lock held and,
+ * Returns %NULL on failure, with @q->queue_lock held.
+ * Returns !%NULL on success, with @q->queue_lock *not held*.
*/
static struct request *get_request_wait(struct request_queue *q, int rw_flags,
struct bio *bio)
struct io_context *ioc;
struct request_list *rl = &q->rq;
+ if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags)))
+ return NULL;
+
prepare_to_wait_exclusive(&rl->wait[is_sync], &wait,
TASK_UNINTERRUPTIBLE);
{
struct request *rq;
- if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags)))
- return NULL;
-
BUG_ON(rw != READ && rw != WRITE);
spin_lock_irq(q->queue_lock);
- if (gfp_mask & __GFP_WAIT) {
+ if (gfp_mask & __GFP_WAIT)
rq = get_request_wait(q, rw, NULL);
- } else {
+ else
rq = get_request(q, rw, NULL, gfp_mask);
- if (!rq)
- spin_unlock_irq(q->queue_lock);
- }
+ if (!rq)
+ spin_unlock_irq(q->queue_lock);
/* q->queue_lock is unlocked at this point */
return rq;
* it didn't come out of our reserved rq pools
*/
if (req->cmd_flags & REQ_ALLOCED) {
- int is_sync = rq_is_sync(req) != 0;
- int priv = req->cmd_flags & REQ_ELVPRIV;
+ unsigned int flags = req->cmd_flags;
BUG_ON(!list_empty(&req->queuelist));
BUG_ON(!hlist_unhashed(&req->hash));
blk_free_request(q, req);
- freed_request(q, is_sync, priv);
+ freed_request(q, flags);
}
}
EXPORT_SYMBOL_GPL(__blk_put_request);
return true;
}
-/*
- * Attempts to merge with the plugged list in the current process. Returns
- * true if merge was successful, otherwise false.
+/**
+ * attempt_plug_merge - try to merge with %current's plugged list
+ * @q: request_queue new bio is being queued at
+ * @bio: new bio being queued
+ * @request_count: out parameter for number of traversed plugged requests
+ *
+ * Determine whether @bio being queued on @q can be merged with a request
+ * on %current's plugged list. Returns %true if merge was successful,
+ * otherwise %false.
+ *
+ * This function is called without @q->queue_lock; however, elevator is
+ * accessed iff there already are requests on the plugged list which in
+ * turn guarantees validity of the elevator.
+ *
+ * Note that, on successful merge, elevator operation
+ * elevator_bio_merged_fn() will be called without queue lock. Elevator
+ * must be ready for this.
*/
-static bool attempt_plug_merge(struct task_struct *tsk, struct request_queue *q,
- struct bio *bio, unsigned int *request_count)
+static bool attempt_plug_merge(struct request_queue *q, struct bio *bio,
+ unsigned int *request_count)
{
struct blk_plug *plug;
struct request *rq;
bool ret = false;
- plug = tsk->plug;
+ plug = current->plug;
if (!plug)
goto out;
*request_count = 0;
void init_request_from_bio(struct request *req, struct bio *bio)
{
- req->cpu = bio->bi_comp_cpu;
req->cmd_type = REQ_TYPE_FS;
req->cmd_flags |= bio->bi_rw & REQ_COMMON_MASK;
blk_rq_bio_prep(req->q, req, bio);
}
-static int __make_request(struct request_queue *q, struct bio *bio)
+void blk_queue_bio(struct request_queue *q, struct bio *bio)
{
const bool sync = !!(bio->bi_rw & REQ_SYNC);
struct blk_plug *plug;
* Check if we can merge with the plugged list before grabbing
* any locks.
*/
- if (attempt_plug_merge(current, q, bio, &request_count))
- goto out;
+ if (attempt_plug_merge(q, bio, &request_count))
+ return;
spin_lock_irq(q->queue_lock);
* Returns with the queue unlocked.
*/
req = get_request_wait(q, rw_flags, bio);
+ if (unlikely(!req)) {
+ bio_endio(bio, -ENODEV); /* @q is dead */
+ goto out_unlock;
+ }
/*
* After dropping the lock and possibly sleeping here, our request
*/
init_request_from_bio(req, bio);
- if (test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags) ||
- bio_flagged(bio, BIO_CPU_AFFINE))
+ if (test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags))
req->cpu = raw_smp_processor_id();
plug = current->plug;
*/
if (list_empty(&plug->list))
trace_block_plug(q);
- else if (!plug->should_sort) {
- struct request *__rq;
+ else {
+ if (!plug->should_sort) {
+ struct request *__rq;
- __rq = list_entry_rq(plug->list.prev);
- if (__rq->q != q)
- plug->should_sort = 1;
+ __rq = list_entry_rq(plug->list.prev);
+ if (__rq->q != q)
+ plug->should_sort = 1;
+ }
+ if (request_count >= BLK_MAX_REQUEST_COUNT) {
+ blk_flush_plug_list(plug, false);
+ trace_block_plug(q);
+ }
}
- if (request_count >= BLK_MAX_REQUEST_COUNT)
- blk_flush_plug_list(plug, false);
list_add_tail(&req->queuelist, &plug->list);
drive_stat_acct(req, 1);
} else {
out_unlock:
spin_unlock_irq(q->queue_lock);
}
-out:
- return 0;
}
+EXPORT_SYMBOL_GPL(blk_queue_bio); /* for device mapper only */
/*
* If bio->bi_dev is a partition, remap the location
return 0;
}
-/**
- * generic_make_request - hand a buffer to its device driver for I/O
- * @bio: The bio describing the location in memory and on the device.
- *
- * generic_make_request() is used to make I/O requests of block
- * devices. It is passed a &struct bio, which describes the I/O that needs
- * to be done.
- *
- * generic_make_request() does not return any status. The
- * success/failure status of the request, along with notification of
- * completion, is delivered asynchronously through the bio->bi_end_io
- * function described (one day) else where.
- *
- * The caller of generic_make_request must make sure that bi_io_vec
- * are set to describe the memory buffer, and that bi_dev and bi_sector are
- * set to describe the device address, and the
- * bi_end_io and optionally bi_private are set to describe how
- * completion notification should be signaled.
- *
- * generic_make_request and the drivers it calls may use bi_next if this
- * bio happens to be merged with someone else, and may change bi_dev and
- * bi_sector for remaps as it sees fit. So the values of these fields
- * should NOT be depended on after the call to generic_make_request.
- */
-static inline void __generic_make_request(struct bio *bio)
+static noinline_for_stack bool
+generic_make_request_checks(struct bio *bio)
{
struct request_queue *q;
- sector_t old_sector;
- int ret, nr_sectors = bio_sectors(bio);
- dev_t old_dev;
+ int nr_sectors = bio_sectors(bio);
int err = -EIO;
+ char b[BDEVNAME_SIZE];
+ struct hd_struct *part;
might_sleep();
if (bio_check_eod(bio, nr_sectors))
goto end_io;
- /*
- * Resolve the mapping until finished. (drivers are
- * still free to implement/resolve their own stacking
- * by explicitly returning 0)
- *
- * NOTE: we don't repeat the blk_size check for each new device.
- * Stacking drivers are expected to know what they are doing.
- */
- old_sector = -1;
- old_dev = 0;
- do {
- char b[BDEVNAME_SIZE];
- struct hd_struct *part;
-
- q = bdev_get_queue(bio->bi_bdev);
- if (unlikely(!q)) {
- printk(KERN_ERR
- "generic_make_request: Trying to access "
- "nonexistent block-device %s (%Lu)\n",
- bdevname(bio->bi_bdev, b),
- (long long) bio->bi_sector);
- goto end_io;
- }
-
- if (unlikely(!(bio->bi_rw & REQ_DISCARD) &&
- nr_sectors > queue_max_hw_sectors(q))) {
- printk(KERN_ERR "bio too big device %s (%u > %u)\n",
- bdevname(bio->bi_bdev, b),
- bio_sectors(bio),
- queue_max_hw_sectors(q));
- goto end_io;
- }
-
- if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags)))
- goto end_io;
-
- part = bio->bi_bdev->bd_part;
- if (should_fail_request(part, bio->bi_size) ||
- should_fail_request(&part_to_disk(part)->part0,
- bio->bi_size))
- goto end_io;
-
- /*
- * If this device has partitions, remap block n
- * of partition p to block n+start(p) of the disk.
- */
- blk_partition_remap(bio);
+ q = bdev_get_queue(bio->bi_bdev);
+ if (unlikely(!q)) {
+ printk(KERN_ERR
+ "generic_make_request: Trying to access "
+ "nonexistent block-device %s (%Lu)\n",
+ bdevname(bio->bi_bdev, b),
+ (long long) bio->bi_sector);
+ goto end_io;
+ }
- if (bio_integrity_enabled(bio) && bio_integrity_prep(bio))
- goto end_io;
+ if (unlikely(!(bio->bi_rw & REQ_DISCARD) &&
+ nr_sectors > queue_max_hw_sectors(q))) {
+ printk(KERN_ERR "bio too big device %s (%u > %u)\n",
+ bdevname(bio->bi_bdev, b),
+ bio_sectors(bio),
+ queue_max_hw_sectors(q));
+ goto end_io;
+ }
- if (old_sector != -1)
- trace_block_bio_remap(q, bio, old_dev, old_sector);
+ part = bio->bi_bdev->bd_part;
+ if (should_fail_request(part, bio->bi_size) ||
+ should_fail_request(&part_to_disk(part)->part0,
+ bio->bi_size))
+ goto end_io;
- old_sector = bio->bi_sector;
- old_dev = bio->bi_bdev->bd_dev;
+ /*
+ * If this device has partitions, remap block n
+ * of partition p to block n+start(p) of the disk.
+ */
+ blk_partition_remap(bio);
- if (bio_check_eod(bio, nr_sectors))
- goto end_io;
+ if (bio_integrity_enabled(bio) && bio_integrity_prep(bio))
+ goto end_io;
- /*
- * Filter flush bio's early so that make_request based
- * drivers without flush support don't have to worry
- * about them.
- */
- if ((bio->bi_rw & (REQ_FLUSH | REQ_FUA)) && !q->flush_flags) {
- bio->bi_rw &= ~(REQ_FLUSH | REQ_FUA);
- if (!nr_sectors) {
- err = 0;
- goto end_io;
- }
- }
+ if (bio_check_eod(bio, nr_sectors))
+ goto end_io;
- if ((bio->bi_rw & REQ_DISCARD) &&
- (!blk_queue_discard(q) ||
- ((bio->bi_rw & REQ_SECURE) &&
- !blk_queue_secdiscard(q)))) {
- err = -EOPNOTSUPP;
+ /*
+ * Filter flush bio's early so that make_request based
+ * drivers without flush support don't have to worry
+ * about them.
+ */
+ if ((bio->bi_rw & (REQ_FLUSH | REQ_FUA)) && !q->flush_flags) {
+ bio->bi_rw &= ~(REQ_FLUSH | REQ_FUA);
+ if (!nr_sectors) {
+ err = 0;
goto end_io;
}
+ }
- if (blk_throtl_bio(q, &bio))
- goto end_io;
-
- /*
- * If bio = NULL, bio has been throttled and will be submitted
- * later.
- */
- if (!bio)
- break;
-
- trace_block_bio_queue(q, bio);
+ if ((bio->bi_rw & REQ_DISCARD) &&
+ (!blk_queue_discard(q) ||
+ ((bio->bi_rw & REQ_SECURE) &&
+ !blk_queue_secdiscard(q)))) {
+ err = -EOPNOTSUPP;
+ goto end_io;
+ }
- ret = q->make_request_fn(q, bio);
- } while (ret);
+ if (blk_throtl_bio(q, bio))
+ return false; /* throttled, will be resubmitted later */
- return;
+ trace_block_bio_queue(q, bio);
+ return true;
end_io:
bio_endio(bio, err);
+ return false;
}
-/*
- * We only want one ->make_request_fn to be active at a time,
- * else stack usage with stacked devices could be a problem.
- * So use current->bio_list to keep a list of requests
- * submited by a make_request_fn function.
- * current->bio_list is also used as a flag to say if
- * generic_make_request is currently active in this task or not.
- * If it is NULL, then no make_request is active. If it is non-NULL,
- * then a make_request is active, and new requests should be added
- * at the tail
+/**
+ * generic_make_request - hand a buffer to its device driver for I/O
+ * @bio: The bio describing the location in memory and on the device.
+ *
+ * generic_make_request() is used to make I/O requests of block
+ * devices. It is passed a &struct bio, which describes the I/O that needs
+ * to be done.
+ *
+ * generic_make_request() does not return any status. The
+ * success/failure status of the request, along with notification of
+ * completion, is delivered asynchronously through the bio->bi_end_io
+ * function described (one day) else where.
+ *
+ * The caller of generic_make_request must make sure that bi_io_vec
+ * are set to describe the memory buffer, and that bi_dev and bi_sector are
+ * set to describe the device address, and the
+ * bi_end_io and optionally bi_private are set to describe how
+ * completion notification should be signaled.
+ *
+ * generic_make_request and the drivers it calls may use bi_next if this
+ * bio happens to be merged with someone else, and may resubmit the bio to
+ * a lower device by calling into generic_make_request recursively, which
+ * means the bio should NOT be touched after the call to ->make_request_fn.
*/
void generic_make_request(struct bio *bio)
{
struct bio_list bio_list_on_stack;
+ if (!generic_make_request_checks(bio))
+ return;
+
+ /*
+ * We only want one ->make_request_fn to be active at a time, else
+ * stack usage with stacked devices could be a problem. So use
+ * current->bio_list to keep a list of requests submited by a
+ * make_request_fn function. current->bio_list is also used as a
+ * flag to say if generic_make_request is currently active in this
+ * task or not. If it is NULL, then no make_request is active. If
+ * it is non-NULL, then a make_request is active, and new requests
+ * should be added at the tail
+ */
if (current->bio_list) {
- /* make_request is active */
bio_list_add(current->bio_list, bio);
return;
}
+
/* following loop may be a bit non-obvious, and so deserves some
* explanation.
* Before entering the loop, bio->bi_next is NULL (as all callers
* We pretend that we have just taken it off a longer list, so
* we assign bio_list to a pointer to the bio_list_on_stack,
* thus initialising the bio_list of new bios to be
- * added. __generic_make_request may indeed add some more bios
+ * added. ->make_request() may indeed add some more bios
* through a recursive call to generic_make_request. If it
* did, we find a non-NULL value in bio_list and re-enter the loop
* from the top. In this case we really did just take the bio
* of the top of the list (no pretending) and so remove it from
- * bio_list, and call into __generic_make_request again.
- *
- * The loop was structured like this to make only one call to
- * __generic_make_request (which is important as it is large and
- * inlined) and to keep the structure simple.
+ * bio_list, and call into ->make_request() again.
*/
BUG_ON(bio->bi_next);
bio_list_init(&bio_list_on_stack);
current->bio_list = &bio_list_on_stack;
do {
- __generic_make_request(bio);
+ struct request_queue *q = bdev_get_queue(bio->bi_bdev);
+
+ q->make_request_fn(q, bio);
+
bio = bio_list_pop(current->bio_list);
} while (bio);
current->bio_list = NULL; /* deactivate */
where = ELEVATOR_INSERT_FLUSH;
add_acct_request(q, rq, where);
+ if (where == ELEVATOR_INSERT_FLUSH)
+ __blk_run_queue(q);
spin_unlock_irqrestore(q->queue_lock, flags);
return 0;
#define PLUG_MAGIC 0x91827364
+/**
+ * blk_start_plug - initialize blk_plug and track it inside the task_struct
+ * @plug: The &struct blk_plug that needs to be initialized
+ *
+ * Description:
+ * Tracking blk_plug inside the task_struct will help with auto-flushing the
+ * pending I/O should the task end up blocking between blk_start_plug() and
+ * blk_finish_plug(). This is important from a performance perspective, but
+ * also ensures that we don't deadlock. For instance, if the task is blocking
+ * for a memory allocation, memory reclaim could end up wanting to free a
+ * page belonging to that request that is currently residing in our private
+ * plug. By flushing the pending I/O when the process goes to sleep, we avoid
+ * this kind of deadlock.
+ */
void blk_start_plug(struct blk_plug *plug)
{
struct task_struct *tsk = current;
git.openpandora.org / pandora-kernel.git / blobdiff