| Message ID | 20201019191928.77845-4-dgilbert@interlog.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v3,1/4] sgl_alloc_order: remove 4 GiB limit, sgl_free() warning | expand |
Am 19.10.20 um 21:19 schrieb Douglas Gilbert: > After enabling copies between scatter gather lists (sgl_s), > another storage related operation is to compare two sgl_s. > This new function is modelled on NVMe's Compare command and > the SCSI VERIFY(BYTCHK=1) command. Like memcmp() this function > returns false on the first miscompare and stops comparing. > > Signed-off-by: Douglas Gilbert <dgilbert@interlog.com> > --- > include/linux/scatterlist.h | 4 +++ > lib/scatterlist.c | 61 +++++++++++++++++++++++++++++++++++++ > 2 files changed, 65 insertions(+) > > diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h > index 6649414c0749..ae260dc5fedb 100644 > --- a/include/linux/scatterlist.h > +++ b/include/linux/scatterlist.h > @@ -325,6 +325,10 @@ size_t sgl_copy_sgl(struct scatterlist *d_sgl, unsigned int d_nents, off_t d_ski > struct scatterlist *s_sgl, unsigned int s_nents, off_t s_skip, > size_t n_bytes); > > +bool sgl_compare_sgl(struct scatterlist *x_sgl, unsigned int x_nents, off_t x_skip, > + struct scatterlist *y_sgl, unsigned int y_nents, off_t y_skip, > + size_t n_bytes); > + > /* > * Maximum number of entries that will be allocated in one piece, if > * a list larger than this is required then chaining will be utilized. > diff --git a/lib/scatterlist.c b/lib/scatterlist.c > index 1f9e093ad7da..49185536acba 100644 > --- a/lib/scatterlist.c > +++ b/lib/scatterlist.c > @@ -1049,3 +1049,64 @@ size_t sgl_copy_sgl(struct scatterlist *d_sgl, unsigned int d_nents, off_t d_ski > } > EXPORT_SYMBOL(sgl_copy_sgl); > > +/** > + * sgl_compare_sgl - Compare x and y (both sgl_s) > + * @x_sgl: x (left) sgl > + * @x_nents: Number of SG entries in x (left) sgl > + * @x_skip: Number of bytes to skip in x (left) before starting > + * @y_sgl: y (right) sgl > + * @y_nents: Number of SG entries in y (right) sgl > + * @y_skip: Number of bytes to skip in y (right) before starting > + * @n_bytes: The (maximum) number of bytes to compare > + * > + * Returns: > + * true if x and y compare equal before x, y or n_bytes is exhausted. > + * Otherwise on a miscompare, returns false (and stops comparing). > + * > + * Notes: > + * x and y are symmetrical: they can be swapped and the result is the same. > + * > + * Implementation is based on memcmp(). x and y segments may overlap. > + * > + * The notes in sgl_copy_sgl() about large sgl_s _applies here as well. > + * > + **/ > +bool sgl_compare_sgl(struct scatterlist *x_sgl, unsigned int x_nents, off_t x_skip, > + struct scatterlist *y_sgl, unsigned int y_nents, off_t y_skip, > + size_t n_bytes) > +{ > + bool equ = true; > + size_t len; > + size_t offset = 0; > + struct sg_mapping_iter x_iter, y_iter; > + > + if (n_bytes == 0) > + return true; > + sg_miter_start(&x_iter, x_sgl, x_nents, SG_MITER_ATOMIC | SG_MITER_FROM_SG); > + sg_miter_start(&y_iter, y_sgl, y_nents, SG_MITER_ATOMIC | SG_MITER_FROM_SG); > + if (!sg_miter_skip(&x_iter, x_skip)) > + goto fini; > + if (!sg_miter_skip(&y_iter, y_skip)) > + goto fini; > + > + while (equ && offset < n_bytes) { > + if (!sg_miter_next(&x_iter)) > + break; > + if (!sg_miter_next(&y_iter)) > + break; > + len = min3(x_iter.length, y_iter.length, n_bytes - offset); > + > + equ = !memcmp(x_iter.addr, y_iter.addr, len); > + offset += len; > + /* LIFO order is important when SG_MITER_ATOMIC is used */ > + y_iter.consumed = len; > + sg_miter_stop(&y_iter); > + x_iter.consumed = len; > + sg_miter_stop(&x_iter); > + } > +fini: > + sg_miter_stop(&y_iter); > + sg_miter_stop(&x_iter); > + return equ; > +} > +EXPORT_SYMBOL(sgl_compare_sgl); > Reviewed-by: Bodo Stroesser <bostroesser@gmail.com>
diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h index 6649414c0749..ae260dc5fedb 100644 --- a/include/linux/scatterlist.h +++ b/include/linux/scatterlist.h @@ -325,6 +325,10 @@ size_t sgl_copy_sgl(struct scatterlist *d_sgl, unsigned int d_nents, off_t d_ski struct scatterlist *s_sgl, unsigned int s_nents, off_t s_skip, size_t n_bytes); +bool sgl_compare_sgl(struct scatterlist *x_sgl, unsigned int x_nents, off_t x_skip, + struct scatterlist *y_sgl, unsigned int y_nents, off_t y_skip, + size_t n_bytes); + /* * Maximum number of entries that will be allocated in one piece, if * a list larger than this is required then chaining will be utilized. diff --git a/lib/scatterlist.c b/lib/scatterlist.c index 1f9e093ad7da..49185536acba 100644 --- a/lib/scatterlist.c +++ b/lib/scatterlist.c @@ -1049,3 +1049,64 @@ size_t sgl_copy_sgl(struct scatterlist *d_sgl, unsigned int d_nents, off_t d_ski } EXPORT_SYMBOL(sgl_copy_sgl); +/** + * sgl_compare_sgl - Compare x and y (both sgl_s) + * @x_sgl: x (left) sgl + * @x_nents: Number of SG entries in x (left) sgl + * @x_skip: Number of bytes to skip in x (left) before starting + * @y_sgl: y (right) sgl + * @y_nents: Number of SG entries in y (right) sgl + * @y_skip: Number of bytes to skip in y (right) before starting + * @n_bytes: The (maximum) number of bytes to compare + * + * Returns: + * true if x and y compare equal before x, y or n_bytes is exhausted. + * Otherwise on a miscompare, returns false (and stops comparing). + * + * Notes: + * x and y are symmetrical: they can be swapped and the result is the same. + * + * Implementation is based on memcmp(). x and y segments may overlap. + * + * The notes in sgl_copy_sgl() about large sgl_s _applies here as well. + * + **/ +bool sgl_compare_sgl(struct scatterlist *x_sgl, unsigned int x_nents, off_t x_skip, + struct scatterlist *y_sgl, unsigned int y_nents, off_t y_skip, + size_t n_bytes) +{ + bool equ = true; + size_t len; + size_t offset = 0; + struct sg_mapping_iter x_iter, y_iter; + + if (n_bytes == 0) + return true; + sg_miter_start(&x_iter, x_sgl, x_nents, SG_MITER_ATOMIC | SG_MITER_FROM_SG); + sg_miter_start(&y_iter, y_sgl, y_nents, SG_MITER_ATOMIC | SG_MITER_FROM_SG); + if (!sg_miter_skip(&x_iter, x_skip)) + goto fini; + if (!sg_miter_skip(&y_iter, y_skip)) + goto fini; + + while (equ && offset < n_bytes) { + if (!sg_miter_next(&x_iter)) + break; + if (!sg_miter_next(&y_iter)) + break; + len = min3(x_iter.length, y_iter.length, n_bytes - offset); + + equ = !memcmp(x_iter.addr, y_iter.addr, len); + offset += len; + /* LIFO order is important when SG_MITER_ATOMIC is used */ + y_iter.consumed = len; + sg_miter_stop(&y_iter); + x_iter.consumed = len; + sg_miter_stop(&x_iter); + } +fini: + sg_miter_stop(&y_iter); + sg_miter_stop(&x_iter); + return equ; +} +EXPORT_SYMBOL(sgl_compare_sgl);
After enabling copies between scatter gather lists (sgl_s), another storage related operation is to compare two sgl_s. This new function is modelled on NVMe's Compare command and the SCSI VERIFY(BYTCHK=1) command. Like memcmp() this function returns false on the first miscompare and stops comparing. Signed-off-by: Douglas Gilbert <dgilbert@interlog.com> --- include/linux/scatterlist.h | 4 +++ lib/scatterlist.c | 61 +++++++++++++++++++++++++++++++++++++ 2 files changed, 65 insertions(+)