ext4: make recently_deleted() properly work with lazy itable initialization

recently_deleted() checks whether inode has been used in the near past.
However this can give false positive result when inode table is not
initialized yet and we are in fact comparing to random garbage (or stale
itable block of a filesystem before mkfs). Ultimately this results in
uninitialized inodes being skipped during inode allocation and possibly
they are never initialized and thus e2fsck complains.  Verify if the
inode has been initialized before checking for dtime.

Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Link: https://patch.msgid.link/20260216164848.3074-3-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org

Author: jankara

fs/ext4/ialloc.c

@@ -686,6 +686,12 @@ static int recently_deleted(struct super_block *sb, ext4_group_t group, int ino)
 	if (unlikely(!gdp))
 		return 0;
 
+	/* Inode was never used in this filesystem? */
+	if (ext4_has_group_desc_csum(sb) &&
+	    (gdp->bg_flags & cpu_to_le16(EXT4_BG_INODE_UNINIT) ||
+	     ino >= EXT4_INODES_PER_GROUP(sb) - ext4_itable_unused_count(sb, gdp)))
+		return 0;
+
 	bh = sb_find_get_block(sb, ext4_inode_table(sb, gdp) +
 		       (ino / inodes_per_block));
 	if (!bh || !buffer_uptodate(bh))