On Thu, Oct 20, 2016 at 8:12 AM, Christoph Hellwig <hch@xxxxxx> wrote:
> Currently the block layer op_is_write, bio_data_dir and rq_data_dir
> helper treat every operation that is not a READ as a data out operation.
> This worked surprisingly long, but the new REQ_OP_ZONE_REPORT operation
> actually adds a second operation that reads data from the device.
> Surprisingly nothing critical relied on this direction, but this might
> be a good opportunity to properly fix this issue up.
>
> We take a little inspiration and use the least significant bit of the
> operation number to encode the data direction, which just requires us
> to renumber the operations to fix this scheme.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
> include/linux/blk_types.h | 38 ++++++++++++++++++++++++++++++--------
> include/linux/fs.h | 5 -----
> 2 files changed, 30 insertions(+), 13 deletions(-)
>
> diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
> index dca972d..70d0ef1 100644
> --- a/include/linux/blk_types.h
> +++ b/include/linux/blk_types.h
> @@ -131,20 +131,37 @@ struct bio {
> /*
> * Operations and flags common to the bio and request structures.
> * We use 8 bits for encoding the operation, and the remaining 24 for flags.
> + *
> + * The least significant bit of the operation number indicates the data
> + * transfer direction:
> + *
> + * - if the least significant bit is set transfers are TO the device
> + * - if the least significant bit is not set transfers are FROM the device
> + *
> + * If a operation does not transfer data the least significant bit has not
> + * meaning.
s/not/no/
> */
> #define REQ_OP_BITS 8
> #define REQ_OP_MASK ((1 << REQ_OP_BITS) - 1)
> #define REQ_FLAG_BITS 24
>
> enum req_opf {
> - REQ_OP_READ,
> - REQ_OP_WRITE,
> - REQ_OP_DISCARD, /* request to discard sectors */
> - REQ_OP_SECURE_ERASE, /* request to securely erase sectors */
> - REQ_OP_WRITE_SAME, /* write same block many times */
> - REQ_OP_FLUSH, /* request for cache flush */
> - REQ_OP_ZONE_REPORT, /* Get zone information */
> - REQ_OP_ZONE_RESET, /* Reset a zone write pointer */
> + /* read sectors from the device */
> + REQ_OP_READ = 0,
> + /* write sectors to the device */
> + REQ_OP_WRITE = 1,
> + /* flush the volatile write cache */
> + REQ_OP_FLUSH = 2,
> + /* discard sectors */
> + REQ_OP_DISCARD = 3,
> + /* get zone information */
> + REQ_OP_ZONE_REPORT = 4,
> + /* securely erase sectors */
> + REQ_OP_SECURE_ERASE = 5,
> + /* seset a zone write pointer */
> + REQ_OP_ZONE_RESET = 6,
> + /* write the same sector many times */
> + REQ_OP_WRITE_SAME = 7,
>
> REQ_OP_LAST,
> };
> @@ -194,6 +211,11 @@ enum req_flag_bits {
> #define bio_set_op_attrs(bio, op, op_flags) \
> ((bio)->bi_opf |= (op | op_flags))
>
> +static inline bool op_is_write(unsigned int op)
> +{
> + return (op & 1);
> +}
> +
> static inline bool op_is_sync(unsigned int op)
> {
> return (op & REQ_OP_MASK) == REQ_OP_READ || (op & REQ_SYNC);
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 16d2b6e..e3e878f 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -2499,11 +2499,6 @@ extern void make_bad_inode(struct inode *);
> extern bool is_bad_inode(struct inode *);
>
> #ifdef CONFIG_BLOCK
> -static inline bool op_is_write(unsigned int op)
> -{
> - return op == REQ_OP_READ ? false : true;
> -}
> -
> /*
> * return data direction, READ or WRITE
> */
> --
> 2.1.4
Reviewed-by: Shaun Tancheff <shaun.tancheff@xxxxxxxxxxx>
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--
Shaun Tancheff
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