drbd: Replaced md_io_mutex by an atomic: md_io_in_use

The new function drbd_md_get_buffer() aborts waiting for the buffer
in case the disk failes in the meantime.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

diff --git a/drivers/block/drbd/drbd_actlog.c b/drivers/block/drbd/drbd_actlog.c
index c64ca6b..4271352 100644 (file)
--- a/drivers/block/drbd/drbd_actlog.c
+++ b/drivers/block/drbd/drbd_actlog.c
@@ -65,6 +65,23 @@ struct drbd_atodb_wait {
 
 int w_al_write_transaction(struct drbd_conf *, struct drbd_work *, int);
 
+void *drbd_md_get_buffer(struct drbd_conf *mdev)
+{
+       int r;
+
+       wait_event(mdev->misc_wait,
+                  (r = atomic_cmpxchg(&mdev->md_io_in_use, 0, 1)) == 0 ||
+                  mdev->state.disk <= D_FAILED);
+
+       return r ? NULL : page_address(mdev->md_io_page);
+}
+
+void drbd_md_put_buffer(struct drbd_conf *mdev)
+{
+       if (atomic_dec_and_test(&mdev->md_io_in_use))
+               wake_up(&mdev->misc_wait);
+}
+
 static int _drbd_md_sync_page_io(struct drbd_conf *mdev,
                                 struct drbd_backing_dev *bdev,
                                 struct page *page, sector_t sector,
@@ -90,6 +107,7 @@ static int _drbd_md_sync_page_io(struct drbd_conf *mdev,
        bio->bi_end_io = drbd_md_io_complete;
        bio->bi_rw = rw;
 
+       atomic_inc(&mdev->md_io_in_use); /* drbd_md_put_buffer() is in the completion handler */
        if (drbd_insert_fault(mdev, (rw & WRITE) ? DRBD_FAULT_MD_WR : DRBD_FAULT_MD_RD))
                bio_endio(bio, -EIO);
        else
@@ -109,7 +127,7 @@ int drbd_md_sync_page_io(struct drbd_conf *mdev, struct drbd_backing_dev *bdev,
        int offset = 0;
        struct page *iop = mdev->md_io_page;
 
-       D_ASSERT(mutex_is_locked(&mdev->md_io_mutex));
+       D_ASSERT(atomic_read(&mdev->md_io_in_use) == 1);
 
        BUG_ON(!bdev->md_bdev);
 
@@ -326,8 +344,13 @@ w_al_write_transaction(struct drbd_conf *mdev, struct drbd_work *w, int unused)
                return 1;
        }
 
-       mutex_lock(&mdev->md_io_mutex); /* protects md_io_buffer, al_tr_cycle, ... */
-       buffer = (struct al_transaction *)page_address(mdev->md_io_page);
+       buffer = drbd_md_get_buffer(mdev); /* protects md_io_buffer, al_tr_cycle, ... */
+       if (!buffer) {
+               dev_err(DEV, "disk failed while waiting for md_io buffer\n");
+               complete(&((struct update_al_work *)w)->event);
+               put_ldev(mdev);
+               return 1;
+       }
 
        buffer->magic = __constant_cpu_to_be32(DRBD_MAGIC);
        buffer->tr_number = cpu_to_be32(mdev->al_tr_number);
@@ -372,7 +395,7 @@ w_al_write_transaction(struct drbd_conf *mdev, struct drbd_work *w, int unused)
        D_ASSERT(mdev->al_tr_pos < MD_AL_MAX_SIZE);
        mdev->al_tr_number++;
 
-       mutex_unlock(&mdev->md_io_mutex);
+       drbd_md_put_buffer(mdev);
 
        complete(&((struct update_al_work *)w)->event);
        put_ldev(mdev);
@@ -441,8 +464,9 @@ int drbd_al_read_log(struct drbd_conf *mdev, struct drbd_backing_dev *bdev)
        /* lock out all other meta data io for now,
         * and make sure the page is mapped.
         */
-       mutex_lock(&mdev->md_io_mutex);
-       buffer = page_address(mdev->md_io_page);
+       buffer = drbd_md_get_buffer(mdev);
+       if (!buffer)
+               return 0;
 
        /* Find the valid transaction in the log */
        for (i = 0; i <= mx; i++) {
@@ -450,7 +474,7 @@ int drbd_al_read_log(struct drbd_conf *mdev, struct drbd_backing_dev *bdev)
                if (rv == 0)
                        continue;
                if (rv == -1) {
-                       mutex_unlock(&mdev->md_io_mutex);
+                       drbd_md_put_buffer(mdev);
                        return 0;
                }
                cnr = be32_to_cpu(buffer->tr_number);
@@ -476,7 +500,7 @@ int drbd_al_read_log(struct drbd_conf *mdev, struct drbd_backing_dev *bdev)
 
        if (!found_valid) {
                dev_warn(DEV, "No usable activity log found.\n");
-               mutex_unlock(&mdev->md_io_mutex);
+               drbd_md_put_buffer(mdev);
                return 1;
        }
 
@@ -491,7 +515,7 @@ int drbd_al_read_log(struct drbd_conf *mdev, struct drbd_backing_dev *bdev)
                rv = drbd_al_read_tr(mdev, bdev, buffer, i);
                ERR_IF(rv == 0) goto cancel;
                if (rv == -1) {
-                       mutex_unlock(&mdev->md_io_mutex);
+                       drbd_md_put_buffer(mdev);
                        return 0;
                }
 
@@ -532,7 +556,7 @@ cancel:
                mdev->al_tr_pos = 0;
 
        /* ok, we are done with it */
-       mutex_unlock(&mdev->md_io_mutex);
+       drbd_md_put_buffer(mdev);
 
        dev_info(DEV, "Found %d transactions (%d active extents) in activity log.\n",
             transactions, active_extents);

diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index 91e69ff..55cae74 100644 (file)
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -1095,7 +1095,7 @@ struct drbd_conf {
        struct page *md_io_page;        /* one page buffer for md_io */
        struct page *md_io_tmpp;        /* for logical_block_size != 512 */
        struct drbd_md_io md_io;
-       struct mutex md_io_mutex;       /* protects the md_io, md_io_page and md_io_tmpp */
+       atomic_t md_io_in_use;          /* protects the md_io, md_io_page and md_io_tmpp */
        spinlock_t al_lock;
        wait_queue_head_t al_wait;
        struct lru_cache *act_log;      /* activity log */
@@ -1537,8 +1537,10 @@ extern void resume_next_sg(struct drbd_conf *mdev);
 extern void suspend_other_sg(struct drbd_conf *mdev);
 extern int drbd_resync_finished(struct drbd_conf *mdev);
 /* maybe rather drbd_main.c ? */
+extern void *drbd_md_get_buffer(struct drbd_conf *mdev);
+extern void drbd_md_put_buffer(struct drbd_conf *mdev);
 extern int drbd_md_sync_page_io(struct drbd_conf *mdev,
-               struct drbd_backing_dev *bdev, sector_t sector, int rw);
+                               struct drbd_backing_dev *bdev, sector_t sector, int rw);
 extern void drbd_ov_oos_found(struct drbd_conf*, sector_t, int);
 extern void drbd_rs_controller_reset(struct drbd_conf *mdev);
 

diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 16969c2..1b59ab3 100644 (file)
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -3043,8 +3043,8 @@ void drbd_init_set_defaults(struct drbd_conf *mdev)
        atomic_set(&mdev->rs_sect_in, 0);
        atomic_set(&mdev->rs_sect_ev, 0);
        atomic_set(&mdev->ap_in_flight, 0);
+       atomic_set(&mdev->md_io_in_use, 0);
 
-       mutex_init(&mdev->md_io_mutex);
        mutex_init(&mdev->data.mutex);
        mutex_init(&mdev->meta.mutex);
        sema_init(&mdev->data.work.s, 0);
@@ -3722,8 +3722,10 @@ void drbd_md_sync(struct drbd_conf *mdev)
        if (!get_ldev_if_state(mdev, D_FAILED))
                return;
 
-       mutex_lock(&mdev->md_io_mutex);
-       buffer = (struct meta_data_on_disk *)page_address(mdev->md_io_page);
+       buffer = drbd_md_get_buffer(mdev);
+       if (!buffer)
+               goto out;
+
        memset(buffer, 0, 512);
 
        buffer->la_size = cpu_to_be64(drbd_get_capacity(mdev->this_bdev));
@@ -3754,7 +3756,8 @@ void drbd_md_sync(struct drbd_conf *mdev)
         * since we updated it on metadata. */
        mdev->ldev->md.la_size_sect = drbd_get_capacity(mdev->this_bdev);
 
-       mutex_unlock(&mdev->md_io_mutex);
+       drbd_md_put_buffer(mdev);
+out:
        put_ldev(mdev);
 }
 
@@ -3774,8 +3777,9 @@ int drbd_md_read(struct drbd_conf *mdev, struct drbd_backing_dev *bdev)
        if (!get_ldev_if_state(mdev, D_ATTACHING))
                return ERR_IO_MD_DISK;
 
-       mutex_lock(&mdev->md_io_mutex);
-       buffer = (struct meta_data_on_disk *)page_address(mdev->md_io_page);
+       buffer = drbd_md_get_buffer(mdev);
+       if (!buffer)
+               goto out;
 
        if (!drbd_md_sync_page_io(mdev, bdev, bdev->md.md_offset, READ)) {
                /* NOTE: can't do normal error processing here as this is
@@ -3836,7 +3840,8 @@ int drbd_md_read(struct drbd_conf *mdev, struct drbd_backing_dev *bdev)
                mdev->sync_conf.al_extents = 127;
 
  err:
-       mutex_unlock(&mdev->md_io_mutex);
+       drbd_md_put_buffer(mdev);
+ out:
        put_ldev(mdev);
 
        return rv;

diff --git a/drivers/block/drbd/drbd_worker.c b/drivers/block/drbd/drbd_worker.c
index eedfe31..94a128b 100644 (file)
--- a/drivers/block/drbd/drbd_worker.c
+++ b/drivers/block/drbd/drbd_worker.c
@@ -78,6 +78,7 @@ void drbd_md_io_complete(struct bio *bio, int error)
        md_io->error = error;
 
        complete(&md_io->event);
+       drbd_md_put_buffer(mdev);
 }
 
 /* reads on behalf of the partner,