drbd: detach from frozen backing device

* drbd-8.3:
  documentation: Documented detach's --force and disk's --disk-timeout
  drbd: Implemented the disk-timeout option
  drbd: Force flag for the detach operation
  drbd: Allow new IOs while the local disk in in FAILED state
  drbd: Bitmap IO functions can not return prematurely if the disk breaks
  drbd: Added a kref to bm_aio_ctx
  drbd: Hold a reference to ldev while doing meta-data IO
  drbd: Keep a reference to the bio until the completion handler finished
  drbd: Implemented wait_until_done_or_disk_failure()
  drbd: Replaced md_io_mutex by an atomic: md_io_in_use
  drbd: moved md_io into mdev
  drbd: Immediately allow completion of IOs, that wait for IO completions on a failed disk
  drbd: Keep a reference to barrier acked requests

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

1 files changed, 85 insertions, 30 deletions

diff --git a/drivers/block/drbd/drbd_bitmap.c b/drivers/block/drbd/drbd_bitmap.c
index 52c48143b22a..706e5220dd4a 100644
--- a/drivers/block/drbd/drbd_bitmap.c
+++ b/drivers/block/drbd/drbd_bitmap.c
@@ -918,13 +918,22 @@ void drbd_bm_clear_all(struct drbd_conf *mdev)
 struct bm_aio_ctx {
         struct drbd_conf *mdev;
         atomic_t in_flight;
-        struct completion done;
+        unsigned int done;
         unsigned flags;
 #define BM_AIO_COPY_PAGES       1
 #define BM_AIO_WRITE_HINTED     2
         int error;
+        struct kref kref;
 };
 
+static void bm_aio_ctx_destroy(struct kref *kref)
+{
+        struct bm_aio_ctx *ctx = container_of(kref, struct bm_aio_ctx, kref);
+
+        put_ldev(ctx->mdev);
+        kfree(ctx);
+}
+
 /* bv_page may be a copy, or may be the original */
 static void bm_async_io_complete(struct bio *bio, int error)
 {
@@ -968,13 +977,16 @@ static void bm_async_io_complete(struct bio *bio, int error)
 
         bio_put(bio);
 
-        if (atomic_dec_and_test(&ctx->in_flight))
-                complete(&ctx->done);
+        if (atomic_dec_and_test(&ctx->in_flight)) {
+                ctx->done = 1;
+                wake_up(&mdev->misc_wait);
+                kref_put(&ctx->kref, &bm_aio_ctx_destroy);
+        }
 }
 
 static void bm_page_io_async(struct bm_aio_ctx *ctx, int page_nr, int rw) __must_hold(local)
 {
-        struct bio *bio = bio_alloc_drbd(GFP_KERNEL);
+        struct bio *bio = bio_alloc_drbd(GFP_NOIO);
         struct drbd_conf *mdev = ctx->mdev;
         struct drbd_bitmap *b = mdev->bitmap;
         struct page *page;
@@ -1032,12 +1044,7 @@ static void bm_page_io_async(struct bm_aio_ctx *ctx, int page_nr, int rw) __must
  */
 static int bm_rw(struct drbd_conf *mdev, int rw, unsigned flags, unsigned lazy_writeout_upper_idx) __must_hold(local)
 {
-        struct bm_aio_ctx ctx = {
-                .mdev = mdev,
-                .in_flight = ATOMIC_INIT(1),
-                .done = COMPLETION_INITIALIZER_ONSTACK(ctx.done),
-                .flags = flags,
-        };
+        struct bm_aio_ctx *ctx;
         struct drbd_bitmap *b = mdev->bitmap;
         int num_pages, i, count = 0;
         unsigned long now;
@@ -1052,7 +1059,27 @@ static int bm_rw(struct drbd_conf *mdev, int rw, unsigned flags, unsigned lazy_w
          * For lazy writeout, we don't care for ongoing changes to the bitmap,
          * as we submit copies of pages anyways.
          */
-        if (!ctx.flags)
+
+        ctx = kmalloc(sizeof(struct bm_aio_ctx), GFP_NOIO);
+        if (!ctx)
+                return -ENOMEM;
+
+        *ctx = (struct bm_aio_ctx) {
+                .mdev = mdev,
+                .in_flight = ATOMIC_INIT(1),
+                .done = 0,
+                .flags = flags,
+                .error = 0,
+                .kref = { ATOMIC_INIT(2) },
+        };
+
+        if (!get_ldev_if_state(mdev, D_ATTACHING)) {  /* put is in bm_aio_ctx_destroy() */
+                dev_err(DEV, "ASSERT FAILED: get_ldev_if_state() == 1 in bm_rw()\n");
+                err = -ENODEV;
+                goto out;
+        }
+
+        if (!ctx->flags)
                 WARN_ON(!(BM_LOCKED_MASK & b->bm_flags));
 
         num_pages = b->bm_number_of_pages;
@@ -1081,32 +1108,40 @@ static int bm_rw(struct drbd_conf *mdev, int rw, unsigned flags, unsigned lazy_w
                                 continue;
                         }
                 }
-                atomic_inc(&ctx.in_flight);
-                bm_page_io_async(&ctx, i, rw);
+                atomic_inc(&ctx->in_flight);
+                bm_page_io_async(ctx, i, rw);
                 ++count;
                 cond_resched();
         }
 
         /*
-         * We initialize ctx.in_flight to one to make sure bm_async_io_complete
-         * will not complete() early, and decrement / test it here.  If there
+         * We initialize ctx->in_flight to one to make sure bm_async_io_complete
+         * will not set ctx->done early, and decrement / test it here.  If there
          * are still some bios in flight, we need to wait for them here.
+         * If all IO is done already (or nothing had been submitted), there is
+         * no need to wait.  Still, we need to put the kref associated with the
+         * "in_flight reached zero, all done" event.
          */
-        if (!atomic_dec_and_test(&ctx.in_flight))
-                wait_for_completion(&ctx.done);
+        if (!atomic_dec_and_test(&ctx->in_flight))
+                wait_until_done_or_disk_failure(mdev, &ctx->done);
+        else
+                kref_put(&ctx->kref, &bm_aio_ctx_destroy);
 
         /* summary for global bitmap IO */
         if (flags == 0)
                 dev_info(DEV, "bitmap %s of %u pages took %lu jiffies\n",
-                                rw == WRITE ? "WRITE" : "READ",
-                                count, jiffies - now);
+                         rw == WRITE ? "WRITE" : "READ",
+                         count, jiffies - now);
 
-        if (ctx.error) {
+        if (ctx->error) {
                 dev_alert(DEV, "we had at least one MD IO ERROR during bitmap IO\n");
                 drbd_chk_io_error(mdev, 1, true);
-                err = -EIO; /* ctx.error ? */
+                err = -EIO; /* ctx->error ? */
         }
 
+        if (atomic_read(&ctx->in_flight))
+                err = -EIO; /* Disk failed during IO... */
+
         now = jiffies;
         if (rw == WRITE) {
                 drbd_md_flush(mdev);
@@ -1121,6 +1156,8 @@ static int bm_rw(struct drbd_conf *mdev, int rw, unsigned flags, unsigned lazy_w
                 dev_info(DEV, "%s (%lu bits) marked out-of-sync by on disk bit-map.\n",
                      ppsize(ppb, now << (BM_BLOCK_SHIFT-10)), now);
 
+out:
+        kref_put(&ctx->kref, &bm_aio_ctx_destroy);
         return err;
 }
 
@@ -1177,28 +1214,46 @@ int drbd_bm_write_hinted(struct drbd_conf *mdev) __must_hold(local)
  */
 int drbd_bm_write_page(struct drbd_conf *mdev, unsigned int idx) __must_hold(local)
 {
-        struct bm_aio_ctx ctx = {
+        struct bm_aio_ctx *ctx;
+        int err;
+
+        if (bm_test_page_unchanged(mdev->bitmap->bm_pages[idx])) {
+                dynamic_dev_dbg(DEV, "skipped bm page write for idx %u\n", idx);
+                return 0;
+        }
+
+        ctx = kmalloc(sizeof(struct bm_aio_ctx), GFP_NOIO);
+        if (!ctx)
+                return -ENOMEM;
+
+        *ctx = (struct bm_aio_ctx) {
                 .mdev = mdev,
                 .in_flight = ATOMIC_INIT(1),
-                .done = COMPLETION_INITIALIZER_ONSTACK(ctx.done),
+                .done = 0,
                 .flags = BM_AIO_COPY_PAGES,
+                .error = 0,
+                .kref = { ATOMIC_INIT(2) },
         };
 
-        if (bm_test_page_unchanged(mdev->bitmap->bm_pages[idx])) {
-                dynamic_dev_dbg(DEV, "skipped bm page write for idx %u\n", idx);
-                return 0;
+        if (!get_ldev_if_state(mdev, D_ATTACHING)) {  /* put is in bm_aio_ctx_destroy() */
+                dev_err(DEV, "ASSERT FAILED: get_ldev_if_state() == 1 in drbd_bm_write_page()\n");
+                err = -ENODEV;
+                goto out;
         }
 
-        bm_page_io_async(&ctx, idx, WRITE_SYNC);
-        wait_for_completion(&ctx.done);
+        bm_page_io_async(ctx, idx, WRITE_SYNC);
+        wait_until_done_or_disk_failure(mdev, &ctx->done);
 
-        if (ctx.error)
+        if (ctx->error)
                 drbd_chk_io_error(mdev, 1, true);
                 /* that should force detach, so the in memory bitmap will be
                  * gone in a moment as well. */
 
         mdev->bm_writ_cnt++;
-        return ctx.error;
+        err = atomic_read(&ctx->in_flight) ? -EIO : ctx->error;
+ out:
+        kref_put(&ctx->kref, &bm_aio_ctx_destroy);
+        return err;
 }
 
 /* NOTE