On Mon, May 13, 2019 at 03:00:03PM +0200, David Sterba wrote:
> On Fri, May 10, 2019 at 01:15:44PM +0200, Johannes Thumshirn wrote:
> > Currently btrfs_csum_data() relied on the crc32c() wrapper around the crypto
> > framework for calculating the CRCs.
> >
> > As we have our own crypto_shash structure in the fs_info now, we can
> > directly call into the crypto framework without going trough the wrapper.
> >
> > Signed-off-by: Johannes Thumshirn <[email protected]>
> > ---
> > fs/btrfs/disk-io.c | 28 ++++++++++++++++++++++++++--
> > 1 file changed, 26 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> > index fb0b06b7b9f6..0c9ac7b45ce8 100644
> > --- a/fs/btrfs/disk-io.c
> > +++ b/fs/btrfs/disk-io.c
> > @@ -253,12 +253,36 @@ struct extent_map *btree_get_extent(struct
> > btrfs_inode *inode,
> > u32 btrfs_csum_data(struct btrfs_fs_info *fs_info, const char *data,
> > u32 seed, size_t len)
> > {
> > - return crc32c(seed, data, len);
> > + SHASH_DESC_ON_STACK(shash, fs_info->csum_shash);
> > + u32 *ctx = (u32 *)shash_desc_ctx(shash);
> > + u32 retval;
> > + int err;
> > +
> > + shash->tfm = fs_info->csum_shash;
> > + shash->flags = 0;
> > + *ctx = seed;
> > +
> > + err = crypto_shash_update(shash, data, len);
> > + ASSERT(err);
> > +
> > + retval = *ctx;
> > + barrier_data(ctx);
> > +
> > + return retval;
>
> I unfortunatelly had a dive into the crypto API calls and since then I'm
> biased against using it (too much indirection and extra memory
> references). So my idea of this function is:
>
> switch (fs_info->csum_type) {
> case CRC32:
> ... calculate crc32c;
> break;
> case SHA256:
> ... calculate sha56;
> break;
> }
>
> with direct calls to the hash primitives rather than thravelling trough
> the shash.
well at least the crc3c2() call we use does nothing else (from
lib/libcrc32c.c):
u32 crc32c(u32 crc, const void *address, unsigned int length)
{
SHASH_DESC_ON_STACK(shash, tfm);
u32 ret, *ctx = (u32 *)shash_desc_ctx(shash);
int err;
shash->tfm = tfm;
shash->flags = 0;
*ctx = crc;
err = crypto_shash_update(shash, address, length);
BUG_ON(err);
ret = *ctx;
barrier_data(ctx);
return ret;
}
EXPORT_SYMBOL(crc32c);
--
Johannes Thumshirn SUSE Labs Filesystems
[email protected] +49 911 74053 689
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Felix Imendörffer, Mary Higgins, Sri Rasiah
HRB 21284 (AG Nürnberg)
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