linux-ext4 - [PATCH v4 6/7] ext4: Enable support for ext4 multi-fsblock atomic write using bigalloc

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Message-ID: <59a68459ff90762db2b440ce2d2e68191324492d.1747289779.git.ritesh.list@gmail.com>
Date: Thu, 15 May 2025 20:15:38 +0530
From: "Ritesh Harjani (IBM)" <ritesh.list@...il.com>
To: linux-ext4@...r.kernel.org
Cc: Theodore Ts'o <tytso@....edu>,
	Jan Kara <jack@...e.cz>,
	John Garry <john.g.garry@...cle.com>,
	djwong@...nel.org,
	Ojaswin Mujoo <ojaswin@...ux.ibm.com>,
	linux-fsdevel@...r.kernel.org,
	"Ritesh Harjani (IBM)" <ritesh.list@...il.com>
Subject: [PATCH v4 6/7] ext4: Enable support for ext4 multi-fsblock atomic write using bigalloc

Last couple of patches added the needed support for multi-fsblock atomic
writes using bigalloc. This patch ensures that filesystem advertizes the
needed atomic write unit min and max values for enabling multi-fsblock
atomic write support with bigalloc.

Co-developed-by: Ojaswin Mujoo <ojaswin@...ux.ibm.com>
Signed-off-by: Ojaswin Mujoo <ojaswin@...ux.ibm.com>
Acked-by: Darrick J. Wong <djwong@...nel.org>
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@...il.com>
---
 fs/ext4/super.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 181934499624..c6fdb8950535 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -4441,13 +4441,16 @@ static int ext4_handle_clustersize(struct super_block *sb)
 
 /*
  * ext4_atomic_write_init: Initializes filesystem min & max atomic write units.
+ * With non-bigalloc filesystem awu will be based upon filesystem blocksize
+ * & bdev awu units.
+ * With bigalloc it will be based upon bigalloc cluster size & bdev awu units.
  * @sb: super block
- * TODO: Later add support for bigalloc
  */
 static void ext4_atomic_write_init(struct super_block *sb)
 {
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
 	struct block_device *bdev = sb->s_bdev;
+	unsigned int clustersize = EXT4_CLUSTER_SIZE(sb);
 
 	if (!bdev_can_atomic_write(bdev))
 		return;
@@ -4457,7 +4460,7 @@ static void ext4_atomic_write_init(struct super_block *sb)
 
 	sbi->s_awu_min = max(sb->s_blocksize,
 			      bdev_atomic_write_unit_min_bytes(bdev));
-	sbi->s_awu_max = min(sb->s_blocksize,
+	sbi->s_awu_max = min(clustersize,
 			      bdev_atomic_write_unit_max_bytes(bdev));
 	if (sbi->s_awu_min && sbi->s_awu_max &&
 	    sbi->s_awu_min <= sbi->s_awu_max) {
-- 
2.49.0