ext4: introduce ext4_sb_breadahead_unmovable() to replace sb_breadahead_unmovable()

If we readahead inode tables in __ext4_get_inode_loc(), it may bypass
buffer_write_io_error() check, so introduce ext4_sb_breadahead_unmovable()
to handle this special case.

This patch also replace sb_breadahead_unmovable() in ext4_fill_super()
for the sake of unification.
Signed-off-by: zhangyi (F) <yi.zhang@huawei.com>
Link: https://lore.kernel.org/r/20200924073337.861472-6-yi.zhang@huawei.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/ext4.h

@@ -2828,6 +2828,7 @@ extern void ext4_read_bh_nowait(struct buffer_head *bh, int op_flags,
 extern int ext4_read_bh(struct buffer_head *bh, int op_flags,
 			bh_end_io_t *end_io);
 extern int ext4_read_bh_lock(struct buffer_head *bh, int op_flags, bool wait);
+extern void ext4_sb_breadahead_unmovable(struct super_block *sb, sector_t block);
 extern int ext4_seq_options_show(struct seq_file *seq, void *offset);
 extern int ext4_calculate_overhead(struct super_block *sb);
 extern void ext4_superblock_csum_set(struct super_block *sb);

fs/ext4/inode.c

@@ -4381,7 +4381,7 @@ static int __ext4_get_inode_loc(struct inode *inode,
 			if (end > table)
 				end = table;
 			while (b <= end)
-				sb_breadahead_unmovable(sb, b++);
+				ext4_sb_breadahead_unmovable(sb, b++);
 		}
 
 		/*

fs/ext4/super.c

@@ -229,6 +229,16 @@ ext4_sb_bread(struct super_block *sb, sector_t block, int op_flags)
 	return bh;
 }
 
+void ext4_sb_breadahead_unmovable(struct super_block *sb, sector_t block)
+{
+	struct buffer_head *bh = sb_getblk_gfp(sb, block, 0);
+
+	if (likely(bh)) {
+		ext4_read_bh_lock(bh, REQ_RAHEAD, false);
+		brelse(bh);
+	}
+}
+
 static int ext4_verify_csum_type(struct super_block *sb,
 				 struct ext4_super_block *es)
 {
@@ -4556,7 +4566,7 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 	/* Pre-read the descriptors into the buffer cache */
 	for (i = 0; i < db_count; i++) {
 		block = descriptor_loc(sb, logical_sb_block, i);
-		sb_breadahead_unmovable(sb, block);
+		ext4_sb_breadahead_unmovable(sb, block);
 	}
 
 	for (i = 0; i < db_count; i++) {