ext4: propagate errors from ext4_sb_bread() in ext4_xattr_block_cache_find()

In ext4_xattr_block_cache_find(), when ext4_sb_bread() returns an error,
we will either continue to find the next ea block or return NULL to try to
insert a new ea block. But whether ext4_sb_bread() returns -EIO or -ENOMEM,
the next operation is most likely to fail with the same error. So propagate
the error returned by ext4_sb_bread() to make ext4_xattr_block_set() fail
to reduce pointless operations.

Signed-off-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20240504075526.2254349-3-libaokun@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Author: LiBaokun96

fs/ext4/xattr.c

@@ -2028,8 +2028,13 @@ ext4_xattr_block_set(handle_t *handle, struct inode *inode,
 
 inserted:
 	if (!IS_LAST_ENTRY(s->first)) {
-		new_bh = ext4_xattr_block_cache_find(inode, header(s->base),
-						     &ce);
+		new_bh = ext4_xattr_block_cache_find(inode, header(s->base), &ce);
+		if (IS_ERR(new_bh)) {
+			error = PTR_ERR(new_bh);
+			new_bh = NULL;
+			goto cleanup;
+		}
+
 		if (new_bh) {
 			/* We found an identical block in the cache. */
 			if (new_bh == bs->bh)
@@ -3094,8 +3099,8 @@ ext4_xattr_cmp(struct ext4_xattr_header *header1,
  *
  * Find an identical extended attribute block.
  *
- * Returns a pointer to the block found, or NULL if such a block was
- * not found or an error occurred.
+ * Returns a pointer to the block found, or NULL if such a block was not
+ * found, or an error pointer if an error occurred while reading ea block.
  */
 static struct buffer_head *
 ext4_xattr_block_cache_find(struct inode *inode,
@@ -3117,13 +3122,11 @@ ext4_xattr_block_cache_find(struct inode *inode,
 
 		bh = ext4_sb_bread(inode->i_sb, ce->e_value, REQ_PRIO);
 		if (IS_ERR(bh)) {
-			if (PTR_ERR(bh) == -ENOMEM) {
-				mb_cache_entry_put(ea_block_cache, ce);
-				return NULL;
-			}
-			bh = NULL;
-			EXT4_ERROR_INODE(inode, "block %lu read error",
-					 (unsigned long)ce->e_value);
+			if (PTR_ERR(bh) != -ENOMEM)
+				EXT4_ERROR_INODE(inode, "block %lu read error",
+						 (unsigned long)ce->e_value);
+			mb_cache_entry_put(ea_block_cache, ce);
+			return bh;
 		} else if (ext4_xattr_cmp(header, BHDR(bh)) == 0) {
 			*pce = ce;
 			return bh;