From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: stable@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	patches@lists.linux.dev,
	Baokun Li <libaokun1@huawei.com>,
	Zhang Yi <yi.zhang@huawei.com>,
	Jan Kara <jack@suse.cz>,
	Pedro Falcato <pfalcato@suse.de>,
	stable@kernel.org,
	Theodore Tso <tytso@mit.edu>
Subject: [PATCH 6.18 620/641] ext4: always allocate blocks only from groups inode can use
Date: Tue, 24 Feb 2026 17:25:46 -0800
Message-ID: <20260225012403.530713904@linuxfoundation.org>
In-Reply-To: <20260225012348.915798704@linuxfoundation.org>
References: <20260225012348.915798704@linuxfoundation.org>
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6.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jan Kara <jack@suse.cz>

commit 4865c768b563deff1b6a6384e74a62f143427b42 upstream.

For filesystems with more than 2^32 blocks inodes using indirect block
based format cannot use blocks beyond the 32-bit limit.
ext4_mb_scan_groups_linear() takes care to not select these unsupported
groups for such inodes however other functions selecting groups for
allocation don't. So far this is harmless because the other selection
functions are used only with mb_optimize_scan and this is currently
disabled for inodes with indirect blocks however in the following patch
we want to enable mb_optimize_scan regardless of inode format.

Reviewed-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Acked-by: Pedro Falcato <pfalcato@suse.de>
Cc: stable@kernel.org
Link: https://patch.msgid.link/20260114182836.14120-3-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/ext4/mballoc.c |   29 ++++++++++++++++++++---------
 1 file changed, 20 insertions(+), 9 deletions(-)

--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -892,6 +892,21 @@ mb_update_avg_fragment_size(struct super
 	}
 }
 
+static ext4_group_t ext4_get_allocation_groups_count(
+				struct ext4_allocation_context *ac)
+{
+	ext4_group_t ngroups = ext4_get_groups_count(ac->ac_sb);
+
+	/* non-extent files are limited to low blocks/groups */
+	if (!(ext4_test_inode_flag(ac->ac_inode, EXT4_INODE_EXTENTS)))
+		ngroups = EXT4_SB(ac->ac_sb)->s_blockfile_groups;
+
+	/* Pairs with smp_wmb() in ext4_update_super() */
+	smp_rmb();
+
+	return ngroups;
+}
+
 static int ext4_mb_scan_groups_xa_range(struct ext4_allocation_context *ac,
 					struct xarray *xa,
 					ext4_group_t start, ext4_group_t end)
@@ -899,7 +914,7 @@ static int ext4_mb_scan_groups_xa_range(
 	struct super_block *sb = ac->ac_sb;
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
 	enum criteria cr = ac->ac_criteria;
-	ext4_group_t ngroups = ext4_get_groups_count(sb);
+	ext4_group_t ngroups = ext4_get_allocation_groups_count(ac);
 	unsigned long group = start;
 	struct ext4_group_info *grp;
 
@@ -951,7 +966,7 @@ static int ext4_mb_scan_groups_p2_aligne
 	ext4_group_t start, end;
 
 	start = group;
-	end = ext4_get_groups_count(ac->ac_sb);
+	end = ext4_get_allocation_groups_count(ac);
 wrap_around:
 	for (i = ac->ac_2order; i < MB_NUM_ORDERS(ac->ac_sb); i++) {
 		ret = ext4_mb_scan_groups_largest_free_order_range(ac, i,
@@ -1001,7 +1016,7 @@ static int ext4_mb_scan_groups_goal_fast
 	ext4_group_t start, end;
 
 	start = group;
-	end = ext4_get_groups_count(ac->ac_sb);
+	end = ext4_get_allocation_groups_count(ac);
 wrap_around:
 	i = mb_avg_fragment_size_order(ac->ac_sb, ac->ac_g_ex.fe_len);
 	for (; i < MB_NUM_ORDERS(ac->ac_sb); i++) {
@@ -1083,7 +1098,7 @@ static int ext4_mb_scan_groups_best_avai
 		min_order = fls(ac->ac_o_ex.fe_len);
 
 	start = group;
-	end = ext4_get_groups_count(ac->ac_sb);
+	end = ext4_get_allocation_groups_count(ac);
 wrap_around:
 	for (i = order; i >= min_order; i--) {
 		int frag_order;
@@ -1182,11 +1197,7 @@ static int ext4_mb_scan_groups(struct ex
 	int ret = 0;
 	ext4_group_t start;
 	struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
-	ext4_group_t ngroups = ext4_get_groups_count(ac->ac_sb);
-
-	/* non-extent files are limited to low blocks/groups */
-	if (!(ext4_test_inode_flag(ac->ac_inode, EXT4_INODE_EXTENTS)))
-		ngroups = sbi->s_blockfile_groups;
+	ext4_group_t ngroups = ext4_get_allocation_groups_count(ac);
 
 	/* searching for the right group start from the goal value specified */
 	start = ac->ac_g_ex.fe_group;