[RFC PATCH 06/10] Introduce REQ_POST_READ_PROC bio flag

[Chandan Rajendra <chandan@linux.ibm.com>]

Ext4 and F2FS currently use a non-NULL value stored at bio->bi_private
to determine if the contents of the bio need to be "post processed"
i.e. whether its contents need to be decrypted and/or verified. For
block size < page size scenario, bio->bi_private would hold a pointer to
buffer_head. Hence, this commit adds the new flag REQ_POST_READ_PROC to
be able to decisively check for post process requirement for a bio.

Signed-off-by: Chandan Rajendra <chandan@linux.ibm.com>
---
 fs/ext4/readpage.c        | 11 +++++++++--
 fs/post_read_process.c    |  2 +-
 include/linux/blk_types.h |  2 ++
 3 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/fs/ext4/readpage.c b/fs/ext4/readpage.c
index 8943fc41fd33..c7dbab35deaa 100644
--- a/fs/ext4/readpage.c
+++ b/fs/ext4/readpage.c
@@ -245,6 +245,7 @@ int ext4_mpage_readpages(struct address_space *mapping,
 		}
 		if (bio == NULL) {
 			struct bio_post_read_ctx *ctx;
+			unsigned int op_flags = 0;
 
 			bio = bio_alloc(GFP_KERNEL,
 				min_t(int, nr_pages, BIO_MAX_PAGES));
@@ -259,8 +260,14 @@ int ext4_mpage_readpages(struct address_space *mapping,
 			bio->bi_iter.bi_sector = blocks[0] << (blkbits - 9);
 			bio->bi_end_io = mpage_end_io;
 			bio->bi_private = ctx;
-			bio_set_op_attrs(bio, REQ_OP_READ,
-						is_readahead ? REQ_RAHEAD : 0);
+
+			if (is_readahead)
+				op_flags |= REQ_RAHEAD;
+
+			if (ctx)
+				op_flags |= REQ_POST_READ_PROC;
+
+			bio_set_op_attrs(bio, REQ_OP_READ, op_flags);
 		}
 
 		length = first_hole << blkbits;
diff --git a/fs/post_read_process.c b/fs/post_read_process.c
index 1f8663d70247..66c1c6e57e70 100644
--- a/fs/post_read_process.c
+++ b/fs/post_read_process.c
@@ -104,7 +104,7 @@ void put_bio_post_read_ctx(struct bio_post_read_ctx *ctx)
 
 bool bio_post_read_required(struct bio *bio)
 {
-	return bio->bi_private && !bio->bi_status;
+	return bio->bi_opf & REQ_POST_READ_PROC;
 }
 
 static int __init bio_init_post_read_processing(void)
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 5c7e7f859a24..6904945c8c40 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -320,6 +320,7 @@ enum req_flag_bits {
 	__REQ_RAHEAD,		/* read ahead, can fail anytime */
 	__REQ_BACKGROUND,	/* background IO */
 	__REQ_NOWAIT,           /* Don't wait if request will block */
+	__REQ_POST_READ_PROC,
 
 	/* command specific flags for REQ_OP_WRITE_ZEROES: */
 	__REQ_NOUNMAP,		/* do not free blocks when zeroing */
@@ -346,6 +347,7 @@ enum req_flag_bits {
 #define REQ_RAHEAD		(1ULL << __REQ_RAHEAD)
 #define REQ_BACKGROUND		(1ULL << __REQ_BACKGROUND)
 #define REQ_NOWAIT		(1ULL << __REQ_NOWAIT)
+#define REQ_POST_READ_PROC	(1ULL << __REQ_POST_READ_PROC)
 #define REQ_NOUNMAP		(1ULL << __REQ_NOUNMAP)
 #define REQ_HIPRI		(1ULL << __REQ_HIPRI)
 
-- 
2.19.1