btrfs: Fix calculate typo caused by ambiguous meaning of logic_end

Commit Message

Zhaolei July 21, 2015, 7:42 a.m. UTC

From: Zhao Lei <[e-mail]>

For example, in scrub_raid56_parity(), following lines are used
to judge is all data processed:
 place1: if (key.objectid > logic_end) ...
 place2: if (logic_start >= logic_end) ...
 ...
 (place2 is typo, is should be ">", it is copied from other
  place, where logic_end's meaning is different, long story...)

We can fix above typo directly, but the root reason is ambiguous
meaning of logic_end in scrub raid56 parity.

In other place, XXX_end is pointed to data which is not included,
and we need to process segment of [XXX_start, XXX_end).

But for scrub raid56 parity, logic_end is pointed to lattest data
need to process, and introduced many "+ 1" and "- 1" in code as
below:
 length = sparity->logic_end - sparity->logic_start + 1
 logic_end - logic_start + 1
 stripe_logical + increment - 1

This patch changed logic_end's meaning to make it in normal understanding
in raid56 parity functions and data struct alone with above bugfix.

Signed-off-by: Zhao Lei <[e-mail]>
---
 fs/btrfs/scrub.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

Patch

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index 24720f6..7f56603 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -2702,7 +2702,7 @@  static void scrub_parity_check_and_repair(struct scrub_parity *sparity)
 			   sparity->nsectors))
 		goto out;
 
-	length = sparity->logic_end - sparity->logic_start + 1;
+	length = sparity->logic_end - sparity->logic_start;
 	ret = btrfs_map_sblock(sctx->dev_root->fs_info, WRITE,
 			       sparity->logic_start,
 			       &length, &bbio, 0, 1);
@@ -2868,7 +2868,7 @@  static noinline_for_stack int scrub_raid56_parity(struct scrub_ctx *sctx,
 			    key.type != BTRFS_METADATA_ITEM_KEY)
 				goto next;
 
-			if (key.objectid > logic_end) {
+			if (key.objectid >= logic_end) {
 				stop_loop = 1;
 				break;
 			}
@@ -2957,7 +2957,7 @@  next:
 out:
 	if (ret < 0)
 		scrub_parity_mark_sectors_error(sparity, logic_start,
-						logic_end - logic_start + 1);
+						logic_end - logic_start);
 	scrub_parity_put(sparity);
 	scrub_submit(sctx);
 	mutex_lock(&sctx->wr_ctx.wr_lock);
@@ -3138,7 +3138,7 @@  static noinline_for_stack int scrub_stripe(struct scrub_ctx *sctx,
 			logical += base;
 			if (ret) {
 				stripe_logical += base;
-				stripe_end = stripe_logical + increment - 1;
+				stripe_end = stripe_logical + increment;
 				ret = scrub_raid56_parity(sctx, map, scrub_dev,
 							  ppath, stripe_logical,
 							  stripe_end);
@@ -3284,7 +3284,7 @@  loop:
 					if (ret && physical < physical_end) {
 						stripe_logical += base;
 						stripe_end = stripe_logical +
-								increment - 1;
+								increment;
 						ret = scrub_raid56_parity(sctx,
 							map, scrub_dev, ppath,
 							stripe_logical,