linux-ext4 - [PATCH v3 12/18] ext4: Return error from ext4

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Date:   Fri, 16 Oct 2020 17:04:37 +0100
From:   "Matthew Wilcox (Oracle)" <willy@...radead.org>
To:     linux-fsdevel@...r.kernel.org
Cc:     "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        linux-mm@...ck.org, "Theodore Ts'o" <tytso@....edu>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        linux-ext4@...r.kernel.org
Subject: [PATCH v3 12/18] ext4: Return error from ext4_readpage

The error returned from ext4_map_blocks() was being discarded, leading
to the generic -EIO being returned to userspace.  Now ext4 can return
more precise errors.

Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
---
 fs/ext4/readpage.c | 24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/fs/ext4/readpage.c b/fs/ext4/readpage.c
index f014c5e473a9..00a024f3a954 100644
--- a/fs/ext4/readpage.c
+++ b/fs/ext4/readpage.c
@@ -237,7 +237,7 @@ int ext4_mpage_readpages(struct inode *inode,
 	sector_t blocks[MAX_BUF_PER_PAGE];
 	unsigned page_block;
 	struct block_device *bdev = inode->i_sb->s_bdev;
-	int length;
+	int length, err = 0;
 	unsigned relative_block = 0;
 	struct ext4_map_blocks map;
 	unsigned int nr_pages = rac ? readahead_count(rac) : 1;
@@ -301,14 +301,9 @@ int ext4_mpage_readpages(struct inode *inode,
 				map.m_lblk = block_in_file;
 				map.m_len = last_block - block_in_file;
 
-				if (ext4_map_blocks(NULL, inode, &map, 0) < 0) {
-				set_error_page:
-					SetPageError(page);
-					zero_user_segment(page, 0,
-							  PAGE_SIZE);
-					unlock_page(page);
-					goto next_page;
-				}
+				err = ext4_map_blocks(NULL, inode, &map, 0);
+				if (err < 0)
+					goto err;
 			}
 			if ((map.m_flags & EXT4_MAP_MAPPED) == 0) {
 				fully_mapped = 0;
@@ -395,6 +390,15 @@ int ext4_mpage_readpages(struct inode *inode,
 		} else
 			last_block_in_bio = blocks[blocks_per_page - 1];
 		goto next_page;
+	set_error_page:
+		err = -EIO;
+	err:
+		if (rac) {
+			SetPageError(page);
+			zero_user_segment(page, 0, PAGE_SIZE);
+		}
+		unlock_page(page);
+		goto next_page;
 	confused:
 		if (bio) {
 			submit_bio(bio);
@@ -410,7 +414,7 @@ int ext4_mpage_readpages(struct inode *inode,
 	}
 	if (bio)
 		submit_bio(bio);
-	return 0;
+	return err;
 }
 
 int __init ext4_init_post_read_processing(void)
-- 
2.28.0