diff options
author | Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> | 2011-10-10 08:42:22 +0400 |
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committer | Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> | 2011-10-13 17:48:36 +0400 |
commit | 29bde093787f3bdf7b9b4270ada6be7c8076e36b (patch) | |
tree | 4fff697e0acb2471b1bd575cbd006fa4efc3937d /drivers/block/xen-blkback/blkback.c | |
parent | 469738e675524b6aa029ecd46bdda3f878b12eff (diff) | |
download | linux-29bde093787f3bdf7b9b4270ada6be7c8076e36b.tar.xz |
xen/blkback: Support 'feature-barrier' aka old-style BARRIER requests.
We emulate the barrier requests by draining the outstanding bio's
and then sending the WRITE_FLUSH command. To drain the I/Os
we use the refcnt that is used during disconnect to wait for all
the I/Os before disconnecting from the frontend. We latch on its
value and if it reaches either the threshold for disconnect or when
there are no more outstanding I/Os, then we have drained all I/Os.
Suggested-by: Christopher Hellwig <hch@infradead.org>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Diffstat (limited to 'drivers/block/xen-blkback/blkback.c')
-rw-r--r-- | drivers/block/xen-blkback/blkback.c | 37 |
1 files changed, 35 insertions, 2 deletions
diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c index e0dab614049c..184b1335c8e9 100644 --- a/drivers/block/xen-blkback/blkback.c +++ b/drivers/block/xen-blkback/blkback.c @@ -452,6 +452,23 @@ static void xen_blk_discard(struct xen_blkif *blkif, struct blkif_request *req) make_response(blkif, req->id, req->operation, status); } +static void xen_blk_drain_io(struct xen_blkif *blkif) +{ + atomic_set(&blkif->drain, 1); + do { + wait_for_completion_interruptible_timeout( + &blkif->drain_complete, HZ); + + if (!atomic_read(&blkif->drain)) + break; + /* The initial value is one, and one refcnt taken at the + * start of the xen_blkif_schedule thread. */ + if (atomic_read(&blkif->refcnt) <= 2) + break; + } while (!kthread_should_stop()); + atomic_set(&blkif->drain, 0); +} + /* * Completion callback on the bio's. Called as bh->b_end_io() */ @@ -464,6 +481,11 @@ static void __end_block_io_op(struct pending_req *pending_req, int error) pr_debug(DRV_PFX "flush diskcache op failed, not supported\n"); xen_blkbk_flush_diskcache(XBT_NIL, pending_req->blkif->be, 0); pending_req->status = BLKIF_RSP_EOPNOTSUPP; + } else if ((pending_req->operation == BLKIF_OP_WRITE_BARRIER) && + (error == -EOPNOTSUPP)) { + pr_debug(DRV_PFX "write barrier op failed, not supported\n"); + xen_blkbk_barrier(XBT_NIL, pending_req->blkif->be, 0); + pending_req->status = BLKIF_RSP_EOPNOTSUPP; } else if (error) { pr_debug(DRV_PFX "Buffer not up-to-date at end of operation," " error=%d\n", error); @@ -481,6 +503,10 @@ static void __end_block_io_op(struct pending_req *pending_req, int error) pending_req->operation, pending_req->status); xen_blkif_put(pending_req->blkif); free_req(pending_req); + if (atomic_read(&pending_req->blkif->refcnt) <= 2) { + if (atomic_read(&pending_req->blkif->drain)) + complete(&pending_req->blkif->drain_complete); + } } } @@ -574,7 +600,6 @@ do_block_io_op(struct xen_blkif *blkif) return more_to_do; } - /* * Transmutation of the 'struct blkif_request' to a proper 'struct bio' * and call the 'submit_bio' to pass it to the underlying storage. @@ -591,6 +616,7 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif, int i, nbio = 0; int operation; struct blk_plug plug; + bool drain = false; switch (req->operation) { case BLKIF_OP_READ: @@ -601,6 +627,8 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif, blkif->st_wr_req++; operation = WRITE_ODIRECT; break; + case BLKIF_OP_WRITE_BARRIER: + drain = true; case BLKIF_OP_FLUSH_DISKCACHE: blkif->st_f_req++; operation = WRITE_FLUSH; @@ -609,7 +637,6 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif, blkif->st_ds_req++; operation = REQ_DISCARD; break; - case BLKIF_OP_WRITE_BARRIER: default: operation = 0; /* make gcc happy */ goto fail_response; @@ -668,6 +695,12 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif, } } + /* Wait on all outstanding I/O's and once that has been completed + * issue the WRITE_FLUSH. + */ + if (drain) + xen_blk_drain_io(pending_req->blkif); + /* * If we have failed at this point, we need to undo the M2P override, * set gnttab_set_unmap_op on all of the grant references and perform |