[Devel] [PATCH RHEL7 COMMIT] ploop: replace BLOCK_UNINIT

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-327.10.1.vz7.12.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-327.10.1.vz7.12.2
------>
commit a20b3f8cdaf0af444ecb96993b241fe7232e11d4
Author: Maxim Patlasov <mpatlasov at virtuozzo.com>
Date:   Wed Mar 16 17:20:49 2016 +0400

    ploop: replace BLOCK_UNINIT
    
    Patchset description:
    
    ploop: improve the performance of submit_alloc path
    
    Instead of using pagecache_write_begin/pagecache_write_end method, it is
    beneficial to preallocate space, then write data directly to block-device,
    then convert uninitialized extents (ext4) explicitly.
    
    The following series implements:
     - a preparation patch replcacing BLOCK_UNINIT with em->uninit
     - a patch implementing performance improvement
    
    ===
    This patch description:
    
    Next patch will need em->block_start even for unwritten extents. Instead of
    using em->block_start == ~0, let's introduce new explicit field of 'em'.
    
    https://jira.sw.ru/browse/PSBM-22381
    
    Signed-off-by: Maxim Patlasov <mpatlasov at virtuozzo.com>
    Acked-by: Dmitry Monakhov <dmonakhov at virtuozzo.com>
---
 drivers/block/ploop/io_direct.c     | 10 +++++-----
 drivers/block/ploop/io_direct_map.c |  6 +++---
 drivers/block/ploop/io_direct_map.h |  4 ++--
 3 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/drivers/block/ploop/io_direct.c b/drivers/block/ploop/io_direct.c
index 3678d5b..514af4b 100644
--- a/drivers/block/ploop/io_direct.c
+++ b/drivers/block/ploop/io_direct.c
@@ -135,7 +135,7 @@ dio_submit(struct ploop_io *io, struct ploop_request * preq,
 	if (IS_ERR(em))
 		goto out_em_err;
 
-	if (write && em->block_start == BLOCK_UNINIT) {
+	if (write && em->uninit) {
 		sector_t end = (sector_t)(iblk + 1) << preq->plo->cluster_log;
 		sec = (sector_t)iblk << preq->plo->cluster_log;
 
@@ -147,7 +147,7 @@ dio_submit(struct ploop_io *io, struct ploop_request * preq,
 			em = extent_lookup_create(io, sec, end - sec);
 			if (IS_ERR(em))
 				goto out_em_err;
-			if (em->block_start != BLOCK_UNINIT)
+			if (!em->uninit)
 				goto write_unint_fail;
 
 			sec = em->end;
@@ -191,13 +191,13 @@ dio_submit(struct ploop_io *io, struct ploop_request * preq,
 			em = extent_lookup_create(io, sec, size);
 			if (IS_ERR(em))
 				goto out_em_err;
-			if (write && em->block_start == BLOCK_UNINIT)
+			if (write && em->uninit)
 				goto write_unint_fail;
 		}
 
 		nsec = dio_isec_to_phys(em, sec);
 
-		if (em->block_start != BLOCK_UNINIT &&
+		if (!em->uninit &&
 		     (bio == NULL ||
 		     bio->bi_sector + (bio->bi_size>>9) != nsec)) {
 
@@ -214,7 +214,7 @@ flush_bio:
 		if (copy > ((em->end - sec) << 9))
 			copy = (em->end - sec) << 9;
 
-		if (em->block_start == BLOCK_UNINIT) {
+		if (em->uninit) {
 			void *kaddr = kmap_atomic(bv->bv_page);
 			memset(kaddr + bv->bv_offset + bw.bv_off, 0, copy);
 			kunmap_atomic(kaddr);
diff --git a/drivers/block/ploop/io_direct_map.c b/drivers/block/ploop/io_direct_map.c
index 1146133..3f9a1ae 100644
--- a/drivers/block/ploop/io_direct_map.c
+++ b/drivers/block/ploop/io_direct_map.c
@@ -257,6 +257,7 @@ struct extent_map *ploop_alloc_extent_map(gfp_t mask)
 		atomic_set(&em->refs, 1);
 		INIT_LIST_HEAD(&em->lru_link);
 		atomic_inc(&ploop_extent_maps_count);
+		em->uninit = false;
 	}
 	return em;
 }
@@ -720,12 +721,11 @@ again:
 
 	em->start = fi_extent.fe_logical >> 9;
 	em->end = (fi_extent.fe_logical + fi_extent.fe_length) >> 9;
+	em->block_start = fi_extent.fe_physical >> 9;
 
 	if (fi_extent.fe_flags & FIEMAP_EXTENT_UNWRITTEN) {
-		em->block_start = BLOCK_UNINIT;
+		em->uninit = true;
 	} else {
-		em->block_start = fi_extent.fe_physical >> 9;
-
 		ret = add_extent_mapping(tree, em);
 		if (ret == -EEXIST) {
 			ploop_extent_put(em);
diff --git a/drivers/block/ploop/io_direct_map.h b/drivers/block/ploop/io_direct_map.h
index 4be1c5c..a83d1b3 100644
--- a/drivers/block/ploop/io_direct_map.h
+++ b/drivers/block/ploop/io_direct_map.h
@@ -3,8 +3,6 @@
 
 #include <linux/rbtree.h>
 
-#define BLOCK_UNINIT ~((sector_t) 0)
-
 struct extent_map_tree
 {
 	struct rb_root map;
@@ -28,6 +26,8 @@ struct extent_map
 	sector_t	block_start;
 
 	atomic_t refs;
+
+	bool uninit;
 };
 
 extern int max_extent_map_pages;