From: Zygo Blaxell <ce3g8jdj@umail.furryterror.org>
Date: Wed, 14 Feb 2024 05:10:23 +0000 (-0500)
Subject: zygo: btrfs: prefer aligned dev_extent holes when allocating chunks (v4, handle last... 
X-Git-Url: http://git.hungrycats.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=fd66ce7a8643932159cfee3fd539bfe8529ab35d;p=linux

zygo: btrfs: prefer aligned dev_extent holes when allocating chunks (v4, handle last hole correctly when it is aligned)

zygo: btrfs: prefer aligned dev_extent holes when allocating chunks (v2, right end of the hole)

(cherry picked from commit ded252ea39093671390a526a76c6def61d7e6ac1)

zygo: btrfs: prefer aligned dev_extent holes when allocating chunks (v3, handle last hole correctly)

(cherry picked from commit 825cb15cd8a02a083042cc6fa12767ec1805f92d)

(cherry picked from commit 4ca76de09f5ac2c9354df4effd4bcea41830eb47)
---

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 20a0ac1e1450..7a23feb068cb 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1685,21 +1685,25 @@ again:
 			dev_extent_hole_check(device, &search_start, &hole_size,
 					      num_bytes);
 
-			if (hole_size > max_hole_size) {
+			/*
+			 * Once we find a hole of sufficient size we
+			 * ignore any larger holes that may appear at
+			 * higher device offsets.  If we later find a
+			 * hole that is sufficiently large, but aligned,
+			 * we'll use that instead.
+			 */
+			if (hole_size > max_hole_size && max_hole_size < num_bytes) {
 				max_hole_start = search_start;
 				max_hole_size = hole_size;
 			}
 
 			/*
-			 * If this free space is greater than which we need,
-			 * it must be the max free space that we have found
-			 * until now, so max_hole_start must point to the start
-			 * of this free space and the length of this free space
-			 * is stored in max_hole_size. Thus, we return
-			 * max_hole_start and max_hole_size and go back to the
-			 * caller.
+			 * If we find a hole that is aligned and as large
+			 * as we need, then exit early with that hole.
 			 */
-			if (hole_size >= num_bytes) {
+			if (hole_size >= num_bytes && (search_start & (SZ_1G - 1)) == SZ_1M) {
+				max_hole_start = search_start;
+				max_hole_size = hole_size;
 				ret = 0;
 				goto out;
 			}
@@ -1728,9 +1732,24 @@ next:
 			goto again;
 		}
 
-		if (hole_size > max_hole_size) {
+		/*
+		 * If this is a larger hole it might not be aligned.
+		 * Keep the hole we found above if it was large enough.
+		 */
+		if (hole_size > max_hole_size && max_hole_size < num_bytes) {
+			max_hole_start = search_start;
+			max_hole_size = hole_size;
+		}
+
+		/*
+		 * The last hole may be aligned and longer than any other,
+		 * so do the aligned check and exit early again.
+		 */
+		if (hole_size >= num_bytes && (search_start & (SZ_1G - 1)) == SZ_1M) {
 			max_hole_start = search_start;
 			max_hole_size = hole_size;
+			ret = 0;
+			goto out;
 		}
 	}