> -----Original Message-----
> From: Mike Snitzer <snitzer@xxxxxxxxxx>
> Sent: Tuesday, 10 July 2018 19:30
> To: yael.chemla@xxxxxxxxxxxx
> Cc: 'Milan Broz' <gmazyland@xxxxxxxxx>; Yael Chemla
> <Yael.Chemla@xxxxxxx>; dm-devel@xxxxxxxxxx
> Subject: Re: Q about dm-verity per bio data
>
> On Tue, Jul 10 2018 at 8:58am -0400,
> yael.chemla@xxxxxxxxxxxx <yael.chemla@xxxxxxxxxxxx> wrote:
>
> > Hi Mike and Milan,
> > I'd like to consult with you,
> > I'm trying to rewrite a patch I submitted few month ago according to
> > comments I got, Eric Bigger asked my to adopt the method used in dm-
> crypt for dynamic allocations.
> > ( [PATCH 2/2] md: dm-verity: allow parallel processing of
> > bio blocks)
> >
> > I saw you rewrite lately in verity_ctr (dm-verity-target.c) the
> > alignment and the calculation of ti->per_io_data_size, and also did similar
> modification at crypt_ctr, in dm-crypt.c And I suspect it's the source of my
> problem.
> >
> > In my new patch edition as a preparation for parallelization of requests I've
> added new structure (dm_verity_request ) to the end of dm-verity "per bio
> data" area.
> > And enlarged accordingly the size of per_io_data_size
> >
> > I keep getting kernel panic such as " bad PC value" or cpu salls.
> > I guess there's something related to alignment that is missing
> >
> > Here my code (it's not the complete patch I intend to submit) but it
> demonstrate my modification and triggers the mentioned panics:
> >
> > Please let me know if you see any issues with alignment or
> per_io_data_size size calculation that is missing.
> > Thank you,
> > Yael
> >
> > diff --git a/drivers/md/dm-verity-target.c
> > b/drivers/md/dm-verity-target.c index 0cb81c7ed2bb..8d6fbe1a1ae2
> > 100644
> > --- a/drivers/md/dm-verity-target.c
> > +++ b/drivers/md/dm-verity-target.c
> > @@ -359,6 +359,7 @@ static void verity_for_io_block(struct dm_verity *v,
> struct dm_verity_io *io,
> > * until you consider the typical block size is 4,096B.
> > * Going through this loops twice should be very rare.
> > */
> > sg_set_page(&sg[*nents], bv.bv_page, len, bv.bv_offset);
> >
> > bio_advance_iter(bio, iter, len);
>
> This hunk doesn't have any change.. and in general when I attempt to apply
> the patch I get:
>
> patching file drivers/md/dm-verity-target.c
> patch: **** malformed patch at line 33: @@ -447,6 +448,10 @@ static int
> verity_verify_io(struct dm_verity_io *io)
>
I minimized my patch to only the structure addition to per bio data, all the rest was omitted. I wanted to consult with you on this matter only.
And I'm sorry for sending diff between files instead of a patch format, moreover there's a patch that comes before it, therfore you got this hunk.
> > @@ -447,6 +448,10 @@ static int verity_verify_io(struct dm_verity_io *io)
> > unsigned int total_len = 0;
> > sector_t cur_block = io->block + b;
> > struct ahash_request *req = verity_io_hash_req(v, io);
> > + struct dm_verity_request *vreq = verity_io_req(io);
> > +
> > + vreq->sg = sg;
> > + vreq->cur_block = cur_block;
> >
> > if (v->validated_blocks &&
> > likely(test_bit(cur_block, v->validated_blocks)))
> > { @@ -641,6 +646,7 @@ static int verity_map(struct dm_target *ti, struct
> bio *bio)
> > bio->bi_end_io = verity_end_io;
> > bio->bi_private = io;
> > io->iter = bio->bi_iter;
> > + io->vreq = (struct dm_verity_request *)((struct
> > + dm_verity_fec_io *)verity_io_digest_end(v, io) + 1);
> >
> > verity_fec_init_io(io);
> >
>
> The above looks very wrong, 2 issues I'm seeing:
>
> 1)
> your new 'struct dm_verity_request' follows the 'want_digest' in 'struct
> dm_verity_io' right?
You're right currently documentation is misleading, it's actually after everything that resides in per bio data.
thus dmverity per bio data looks as follows:
u8 hash_req[v->ahash_reqsize];
u8 real_digest[v->digest_size];
u8 want_digest[v->digest_size];
struct dm_verity_fec_io ;
struct dm_verity_request;
therefore io->vreq is set to location after fec_io structure at per bio memory area (see verity_map).
>
> So why are you then advancing from 'want_digest' by 'struct
> dm_verity_fec_io' to point to (struct dm_verity_request *)!?
>
> 'struct dm_verity_fec_io' would still follow all the per-bio-data associated
> with 'struct dm_verity_io'.
>
> And doesn't dm-verity-fec.c:fec_io() need updating so that it skips over your
> 'struct dm_verity_io'?
>
> You need to introduce new helpers, something like this:
>
> diff --git a/drivers/md/dm-verity-fec.c b/drivers/md/dm-verity-fec.c index
> 684af08d0747..f3922421d58d 100644
> --- a/drivers/md/dm-verity-fec.c
> +++ b/drivers/md/dm-verity-fec.c
> @@ -28,7 +28,7 @@ bool verity_fec_is_enabled(struct dm_verity *v)
> */
> static inline struct dm_verity_fec_io *fec_io(struct dm_verity_io *io) {
> - return (struct dm_verity_fec_io *) verity_io_digest_end(io->v, io);
> + return (struct dm_verity_fec_io *) verity_io_end(io);
> }
>
> /*
> diff --git a/drivers/md/dm-verity.h b/drivers/md/dm-verity.h index
> 3441c10b840c..937d580adf0b 100644
> --- a/drivers/md/dm-verity.h
> +++ b/drivers/md/dm-verity.h
> @@ -115,6 +115,17 @@ static inline u8 *verity_io_digest_end(struct
> dm_verity *v,
> return verity_io_want_digest(v, io) + v->digest_size; }
>
> +static inline struct dm_verity_request *verity_io_req(struct
> +dm_verity_io *io) {
> + return (struct dm_verity_request *) verity_io_digest_end(io->v, io); }
> +
> +static inline void *verity_io_end(struct dm_verity_io *io) {
> + struct dm_verity_request *io_req = verity_io_req(io);
> + return io_req + 1;
> +}
> +
> extern int verity_for_bv_block(struct dm_verity *v, struct dm_verity_io *io,
> struct bvec_iter *iter,
> int (*process)(struct dm_verity *v,
>
> 2)
> There is no need to add 'struct dm_verity_request *vreq;' to 'struct
> dm_verity_io':
>
vreq pointer is preparation for same solution as in dm-crypt, where there's a pointer to the request structure either located at per bio memory area, or dynimicly allocated request, see ctx->r.req (dm-crypt.c at crypt_alloc_req_skcipher)
so when certain cipher is done asynchronously (see in crypt_convert handling of -EINPROGRESS) this pointer will point to a dynamically allocated request, while async cipher will be satisfied with the single request structure resides at per bio area.
> > diff --git a/drivers/md/dm-verity.h b/drivers/md/dm-verity.h index
> > 3441c10b840c..6ccf6f215fe3 100644
> > --- a/drivers/md/dm-verity.h
> > +++ b/drivers/md/dm-verity.h
> > @@ -78,19 +78,31 @@ struct dm_verity_io {
> > struct bvec_iter iter;
> >
> > struct work_struct work;
> > -
> > + struct dm_verity_request *vreq;
> > /*
> > * Three variably-size fields follow this struct:
> > *
> > * u8 hash_req[v->ahash_reqsize];
> > * u8 real_digest[v->digest_size];
> > * u8 want_digest[v->digest_size];
> > - *
> > + * struct dm_verity_request
> > * To access them use: verity_io_hash_req(), verity_io_real_digest()
> > * and verity_io_want_digest().
> > */
> > };
>
> Just access it using the correct verity_io_req().
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