[PATCH v2 3/3] staging: erofs: support IO read error injection

[Gao Xiang <gaoxiang25@huawei.com>]

Used to simulate disk IO read error for testing fatal
error tolerance.

Here are the details,
1) use bio->bi_private to indicate super_block
   for non-compressed bios since some (mainly meta)
   pages can be of the corresponding bdev inode;
2) get super_block dynamically for compressed bios,
   therefore it could not inject bios full of staging
   pages, yet it doesn't affect the normal usage.

Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
---
 .../staging/erofs/Documentation/filesystems/erofs.txt  |  1 +
 drivers/staging/erofs/data.c                           | 18 ++++++++++++------
 drivers/staging/erofs/internal.h                       |  6 ++++--
 drivers/staging/erofs/super.c                          |  3 ++-
 drivers/staging/erofs/unzip_vle.c                      | 14 +++++++++-----
 5 files changed, 28 insertions(+), 14 deletions(-)

diff --git a/drivers/staging/erofs/Documentation/filesystems/erofs.txt b/drivers/staging/erofs/Documentation/filesystems/erofs.txt
index 961ec4da7705..74cf84ac48a3 100644
--- a/drivers/staging/erofs/Documentation/filesystems/erofs.txt
+++ b/drivers/staging/erofs/Documentation/filesystems/erofs.txt
@@ -60,6 +60,7 @@ fault_injection=%d     Enable fault injection in all supported types with
                        specified injection rate. Supported injection type:
                        Type_Name                Type_Value
                        FAULT_KMALLOC            0x000000001
+                       FAULT_READ_IO            0x000000002
 (no)user_xattr         Setup Extended User Attributes. Note: xattr is enabled
                        by default if CONFIG_EROFS_FS_XATTR is selected.
 (no)acl                Setup POSIX Access Control List. Note: acl is enabled
diff --git a/drivers/staging/erofs/data.c b/drivers/staging/erofs/data.c
index 526e0dbea5b5..0714061ba888 100644
--- a/drivers/staging/erofs/data.c
+++ b/drivers/staging/erofs/data.c
@@ -17,11 +17,17 @@
 
 static inline void read_endio(struct bio *bio)
 {
+	struct super_block *const sb = bio->bi_private;
 	int i;
 	struct bio_vec *bvec;
-	const blk_status_t err = bio->bi_status;
+	blk_status_t err = bio->bi_status;
 	struct bvec_iter_all iter_all;
 
+	if (time_to_inject(EROFS_SB(sb), FAULT_READ_IO)) {
+		erofs_show_injection_info(FAULT_READ_IO);
+		err = BLK_STS_IOERR;
+	}
+
 	bio_for_each_segment_all(bvec, bio, i, iter_all) {
 		struct page *page = bvec->bv_page;
 
@@ -63,7 +69,7 @@ struct page *__erofs_get_meta_page(struct super_block *sb,
 	if (!PageUptodate(page)) {
 		struct bio *bio;
 
-		bio = erofs_grab_bio(sb, blkaddr, 1, read_endio, nofail);
+		bio = erofs_grab_bio(sb, blkaddr, 1, sb, read_endio, nofail);
 		if (IS_ERR(bio)) {
 			DBG_BUGON(nofail);
 			err = PTR_ERR(bio);
@@ -188,7 +194,8 @@ static inline struct bio *erofs_read_raw_page(struct bio *bio,
 					      unsigned int nblocks,
 					      bool ra)
 {
-	struct inode *inode = mapping->host;
+	struct inode *const inode = mapping->host;
+	struct super_block *const sb = inode->i_sb;
 	erofs_off_t current_block = (erofs_off_t)page->index;
 	int err;
 
@@ -280,9 +287,8 @@ static inline struct bio *erofs_read_raw_page(struct bio *bio,
 		if (nblocks > BIO_MAX_PAGES)
 			nblocks = BIO_MAX_PAGES;
 
-		bio = erofs_grab_bio(inode->i_sb,
-				     blknr, nblocks, read_endio, false);
-
+		bio = erofs_grab_bio(sb, blknr, nblocks, sb,
+				     read_endio, false);
 		if (IS_ERR(bio)) {
 			err = PTR_ERR(bio);
 			bio = NULL;
diff --git a/drivers/staging/erofs/internal.h b/drivers/staging/erofs/internal.h
index a66c7d495c35..c47778b3fabd 100644
--- a/drivers/staging/erofs/internal.h
+++ b/drivers/staging/erofs/internal.h
@@ -44,11 +44,12 @@
 
 enum {
 	FAULT_KMALLOC,
+	FAULT_READ_IO,
 	FAULT_MAX,
 };
 
 #ifdef CONFIG_EROFS_FAULT_INJECTION
-extern char *erofs_fault_name[FAULT_MAX];
+extern const char *erofs_fault_name[FAULT_MAX];
 #define IS_FAULT_SET(fi, type) ((fi)->inject_type & (1 << (type)))
 
 struct erofs_fault_info {
@@ -467,7 +468,7 @@ static inline int z_erofs_map_blocks_iter(struct inode *inode,
 /* data.c */
 static inline struct bio *
 erofs_grab_bio(struct super_block *sb,
-	       erofs_blk_t blkaddr, unsigned int nr_pages,
+	       erofs_blk_t blkaddr, unsigned int nr_pages, void *bi_private,
 	       bio_end_io_t endio, bool nofail)
 {
 	const gfp_t gfp = GFP_NOIO;
@@ -489,6 +490,7 @@ erofs_grab_bio(struct super_block *sb,
 	bio->bi_end_io = endio;
 	bio_set_dev(bio, sb->s_bdev);
 	bio->bi_iter.bi_sector = (sector_t)blkaddr << LOG_SECTORS_PER_BLOCK;
+	bio->bi_private = bi_private;
 	return bio;
 }
 
diff --git a/drivers/staging/erofs/super.c b/drivers/staging/erofs/super.c
index 7b460a3ca4d6..8bee0d3a161b 100644
--- a/drivers/staging/erofs/super.c
+++ b/drivers/staging/erofs/super.c
@@ -142,8 +142,9 @@ static int superblock_read(struct super_block *sb)
 }
 
 #ifdef CONFIG_EROFS_FAULT_INJECTION
-char *erofs_fault_name[FAULT_MAX] = {
+const char *erofs_fault_name[FAULT_MAX] = {
 	[FAULT_KMALLOC]		= "kmalloc",
+	[FAULT_READ_IO]		= "read IO error",
 };
 
 static void __erofs_build_fault_attr(struct erofs_sb_info *sbi,
diff --git a/drivers/staging/erofs/unzip_vle.c b/drivers/staging/erofs/unzip_vle.c
index 8e720bb882c7..566835cf6f2f 100644
--- a/drivers/staging/erofs/unzip_vle.c
+++ b/drivers/staging/erofs/unzip_vle.c
@@ -844,8 +844,8 @@ static void z_erofs_vle_unzip_kickoff(void *ptr, int bios)
 
 static inline void z_erofs_vle_read_endio(struct bio *bio)
 {
-	const blk_status_t err = bio->bi_status;
 	struct erofs_sb_info *sbi = NULL;
+	blk_status_t err = bio->bi_status;
 	unsigned int i;
 	struct bio_vec *bvec;
 	struct bvec_iter_all iter_all;
@@ -857,9 +857,15 @@ static inline void z_erofs_vle_read_endio(struct bio *bio)
 		DBG_BUGON(PageUptodate(page));
 		DBG_BUGON(!page->mapping);
 
-		if (unlikely(!sbi && !z_erofs_is_stagingpage(page)))
+		if (unlikely(!sbi && !z_erofs_is_stagingpage(page))) {
 			sbi = EROFS_SB(page->mapping->host->i_sb);
 
+			if (time_to_inject(sbi, FAULT_READ_IO)) {
+				erofs_show_injection_info(FAULT_READ_IO);
+				err = BLK_STS_IOERR;
+			}
+		}
+
 		/* sbi should already be gotten if the page is managed */
 		if (sbi)
 			cachemngd = erofs_page_is_managed(sbi, page);
@@ -1430,10 +1436,8 @@ static bool z_erofs_vle_submit_all(struct super_block *sb,
 
 		if (!bio) {
 			bio = erofs_grab_bio(sb, first_index + i,
-					     BIO_MAX_PAGES,
+					     BIO_MAX_PAGES, bi_private,
 					     z_erofs_vle_read_endio, true);
-			bio->bi_private = bi_private;
-
 			++nr_bios;
 		}
 
-- 
2.12.2