#include "transaction.h"
#include "print-tree.h"
#include "volumes.h"
+#include "async-thread.h"
struct map_lookup {
u64 type;
return NULL;
}
+/*
+ * we try to collect pending bios for a device so we don't get a large
+ * number of procs sending bios down to the same device. This greatly
+ * improves the schedulers ability to collect and merge the bios.
+ *
+ * But, it also turns into a long list of bios to process and that is sure
+ * to eventually make the worker thread block. The solution here is to
+ * make some progress and then put this work struct back at the end of
+ * the list if the block device is congested. This way, multiple devices
+ * can make progress from a single worker thread.
+ */
+int run_scheduled_bios(struct btrfs_device *device)
+{
+ struct bio *pending;
+ struct backing_dev_info *bdi;
+ struct bio *tail;
+ struct bio *cur;
+ int again = 0;
+ unsigned long num_run = 0;
+
+ bdi = device->bdev->bd_inode->i_mapping->backing_dev_info;
+loop:
+ spin_lock(&device->io_lock);
+
+ /* take all the bios off the list at once and process them
+ * later on (without the lock held). But, remember the
+ * tail and other pointers so the bios can be properly reinserted
+ * into the list if we hit congestion
+ */
+ pending = device->pending_bios;
+ tail = device->pending_bio_tail;
+ WARN_ON(pending && !tail);
+ device->pending_bios = NULL;
+ device->pending_bio_tail = NULL;
+
+ /*
+ * if pending was null this time around, no bios need processing
+ * at all and we can stop. Otherwise it'll loop back up again
+ * and do an additional check so no bios are missed.
+ *
+ * device->running_pending is used to synchronize with the
+ * schedule_bio code.
+ */
+ if (pending) {
+ again = 1;
+ device->running_pending = 1;
+ } else {
+ again = 0;
+ device->running_pending = 0;
+ }
+ spin_unlock(&device->io_lock);
+
+ while(pending) {
+ cur = pending;
+ pending = pending->bi_next;
+ cur->bi_next = NULL;
+ atomic_dec(&device->dev_root->fs_info->nr_async_submits);
+ submit_bio(cur->bi_rw, cur);
+ num_run++;
+
+ /*
+ * we made progress, there is more work to do and the bdi
+ * is now congested. Back off and let other work structs
+ * run instead
+ */
+ if (pending && num_run && bdi_write_congested(bdi)) {
+ struct bio *old_head;
+
+ spin_lock(&device->io_lock);
+ old_head = device->pending_bios;
+ device->pending_bios = pending;
+ if (device->pending_bio_tail)
+ tail->bi_next = old_head;
+ else
+ device->pending_bio_tail = tail;
+
+ spin_unlock(&device->io_lock);
+ btrfs_requeue_work(&device->work);
+ goto done;
+ }
+ }
+ if (again)
+ goto loop;
+done:
+ return 0;
+}
+
+void pending_bios_fn(struct btrfs_work *work)
+{
+ struct btrfs_device *device;
+
+ device = container_of(work, struct btrfs_device, work);
+ run_scheduled_bios(device);
+}
+
static int device_list_add(const char *path,
struct btrfs_super_block *disk_super,
u64 devid, struct btrfs_fs_devices **fs_devices_ret)
return -ENOMEM;
}
device->devid = devid;
+ device->work.func = pending_bios_fn;
memcpy(device->uuid, disk_super->dev_item.uuid,
BTRFS_UUID_SIZE);
device->barriers = 1;
}
device->barriers = 1;
+ device->work.func = pending_bios_fn;
generate_random_uuid(device->uuid);
spin_lock_init(&device->io_lock);
device->name = kstrdup(device_path, GFP_NOFS);
#endif
}
+struct async_sched {
+ struct bio *bio;
+ int rw;
+ struct btrfs_fs_info *info;
+ struct btrfs_work work;
+};
+
+/*
+ * see run_scheduled_bios for a description of why bios are collected for
+ * async submit.
+ *
+ * This will add one bio to the pending list for a device and make sure
+ * the work struct is scheduled.
+ */
+int schedule_bio(struct btrfs_root *root, struct btrfs_device *device,
+ int rw, struct bio *bio)
+{
+ int should_queue = 1;
+
+ /* don't bother with additional async steps for reads, right now */
+ if (!(rw & (1 << BIO_RW))) {
+ submit_bio(rw, bio);
+ return 0;
+ }
+
+ /*
+ * nr_async_sumbits allows us to reliably return congestion to the
+ * higher layers. Otherwise, the async bio makes it appear we have
+ * made progress against dirty pages when we've really just put it
+ * on a queue for later
+ */
+ atomic_inc(&root->fs_info->nr_async_submits);
+ bio->bi_next = NULL;
+ bio->bi_rw |= rw;
+
+ spin_lock(&device->io_lock);
+
+ if (device->pending_bio_tail)
+ device->pending_bio_tail->bi_next = bio;
+
+ device->pending_bio_tail = bio;
+ if (!device->pending_bios)
+ device->pending_bios = bio;
+ if (device->running_pending)
+ should_queue = 0;
+
+ spin_unlock(&device->io_lock);
+
+ if (should_queue)
+ btrfs_queue_worker(&root->fs_info->workers, &device->work);
+ return 0;
+}
+
int btrfs_map_bio(struct btrfs_root *root, int rw, struct bio *bio,
- int mirror_num)
+ int mirror_num, int async_submit)
{
struct btrfs_mapping_tree *map_tree;
struct btrfs_device *dev;
dev = multi->stripes[dev_nr].dev;
if (dev && dev->bdev) {
bio->bi_bdev = dev->bdev;
- spin_lock(&dev->io_lock);
- dev->total_ios++;
- spin_unlock(&dev->io_lock);
- submit_bio(rw, bio);
+ if (async_submit)
+ schedule_bio(root, dev, rw, bio);
+ else
+ submit_bio(rw, bio);
} else {
bio->bi_bdev = root->fs_info->fs_devices->latest_bdev;
bio->bi_sector = logical >> 9;
device->barriers = 1;
device->dev_root = root->fs_info->dev_root;
device->devid = devid;
+ device->work.func = pending_bios_fn;
fs_devices->num_devices++;
spin_lock_init(&device->io_lock);
memcpy(device->uuid, dev_uuid, BTRFS_UUID_SIZE);
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff