7.3-stable review patch. If anyone has any objections, please let me know. ------------------ From: guzebing [ Upstream commit 26a3ff309c91986dbedb05d0e0f0050ea0aa629c ] Commit 97f5ec3b166d ("ext4: prevent delalloc to nodelalloc on remount") rejects switching a mounted filesystem from delalloc to nodelalloc. However, it performs the check after ext4_apply_options() has already cleared EXT4_MOUNT_DELALLOC in the live superblock. The failure path eventually restores the bit, but leaves a window where other CPUs can observe nodelalloc. test_opt() reads s_mount_opt directly without a lock shared with remount. If a concurrent truncate's __es_remove_extent() hits this window and observes nodelalloc, it sets count_reserved to false. Delayed extent status entries are then removed without calculating their cluster reservations, leaving reserved at zero. ext4_es_remove_extent() therefore calls ext4_da_release_space() with zero, leaving i_reserved_data_blocks and s_dirtyclusters_counter elevated. When the inode is later evicted after unlink, ext4_destroy_inode() reports: i_reserved_data_blocks (...) not cleared! CPU 0 CPU 1 ksys_truncate() ... ext4_es_remove_extent() ext4_reconfigure() ext4_check_opt_consistency() __ext4_remount() ext4_apply_options() clear EXT4_MOUNT_DELALLOC __es_remove_extent() test_opt() sees !DELALLOC count_reserved = false reject delalloc -> nodelalloc restore EXT4_MOUNT_DELALLOC remove delayed ES ext4_da_release_space(0) Follow the pre-apply validation approach used by ext4_check_quota_consistency() and reject the transition in ext4_check_opt_consistency(), before ext4_apply_options() changes live state. Use mask_s_mount_opt to determine whether delalloc/nodelalloc was specified and ctx_test_mount_opt() to check the final parsed value. Fixes: 97f5ec3b166d ("ext4: prevent delalloc to nodelalloc on remount") Cc: stable@vger.kernel.org Signed-off-by: guzebing Reviewed-by: Ojaswin Mujoo Reviewed-by: Jan Kara Link: https://patch.msgid.link/20260814034855.1573759-1-guzebing1612@gmail.com Signed-off-by: Theodore Ts'o Signed-off-by: Sasha Levin --- fs/ext4/super.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) diff --git a/fs/ext4/super.c b/fs/ext4/super.c index e790a71475011..a8c4a227edf16 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -2840,6 +2840,14 @@ static int ext4_check_opt_consistency(struct fs_context *fc, } if (is_remount) { + if (test_opt(sb, DELALLOC) && + (ctx->mask_s_mount_opt & EXT4_MOUNT_DELALLOC) && + !ctx_test_mount_opt(ctx, EXT4_MOUNT_DELALLOC)) { + ext4_msg(sb, KERN_ERR, + "can't disable delalloc during remount"); + return -EINVAL; + } + if (!sbi->s_journal && ctx_test_mount_opt(ctx, EXT4_MOUNT_DATA_ERR_ABORT)) { ext4_msg(NULL, KERN_WARNING, @@ -6712,13 +6720,6 @@ static int __ext4_remount(struct fs_context *fc, struct super_block *sb) goto restore_opts; } - if ((old_opts.s_mount_opt & EXT4_MOUNT_DELALLOC) && - !test_opt(sb, DELALLOC)) { - ext4_msg(sb, KERN_ERR, "can't disable delalloc during remount"); - err = -EINVAL; - goto restore_opts; - } - sb->s_flags = (sb->s_flags & ~SB_POSIXACL) | (test_opt(sb, POSIX_ACL) ? SB_POSIXACL : 0); -- 2.53.0