Hi Chandan,
On Mon, Feb 18, 2019 at 03:34:29PM +0530, Chandan Rajendra wrote:
> 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@xxxxxxxxxxxxx>
> ---
> 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
>
>
>
I don't think this is an appropriate use of a request flag, as request flags are
meant for the block layer.
Also doesn't the bio still need a pointer to the bio_post_read_ctx anyway? So I
don't see how this would solve the problem, if ->bi_private is already used.
- Eric
