On 24.10.22 03:02, Douglas Gilbert wrote:
A long time ago this driver's store was allocated by kmalloc() or
alloc_pages(). When this was switched to vmalloc() the author
noticed slower ramdisk access times and more variability in repeated
tests. So try going back with sgl_alloc_order() to get uniformly
sized allocations in a sometimes large scatter gather _array_. That
array is the basis of maintaining O(1) access to the store.
Using sgl_alloc_order() and friends requires CONFIG_SGL_ALLOC
so add a 'select' to the Kconfig file.
Remove kcalloc() in resp_verify() as sgl_s can now be compared
directly without forming an intermediate buffer. This is a
performance win for the SCSI VERIFY command implementation.
Make the SCSI COMPARE AND WRITE command yield the offset of the
first miscompared byte when the compare fails (as required by
T10).
Signed-off-by: Douglas Gilbert <dgilbert@xxxxxxxxxxxx>
---
drivers/scsi/Kconfig | 3 +-
drivers/scsi/scsi_debug.c | 478 +++++++++++++++++++++++++++-----------
2 files changed, 341 insertions(+), 140 deletions(-)
diff --git a/drivers/scsi/Kconfig b/drivers/scsi/Kconfig
index 03e71e3d5e5b..97edb4e17319 100644
--- a/drivers/scsi/Kconfig
+++ b/drivers/scsi/Kconfig
@@ -1229,13 +1229,14 @@ config SCSI_DEBUG
tristate "SCSI debugging host and device simulator"
depends on SCSI
select CRC_T10DIF
+ select SGL_ALLOC
help
This pseudo driver simulates one or more hosts (SCSI initiators),
each with one or more targets, each with one or more logical units.
Defaults to one of each, creating a small RAM disk device. Many
parameters found in the /sys/bus/pseudo/drivers/scsi_debug
directory can be tweaked at run time.
- See <http://sg.danny.cz/sg/sdebug26.html> for more information.
+ See <https://sg.danny.cz/sg/scsi_debug.html> for more information.
Mainly used for testing and best as a module. If unsure, say N.
config SCSI_MESH
diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index 697fc57bc711..0715521b2527 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -221,6 +221,7 @@ static const char *sdebug_version_date = "20210520";
#define SDEBUG_CANQUEUE_WORDS 3 /* a WORD is bits in a long */
#define SDEBUG_CANQUEUE (SDEBUG_CANQUEUE_WORDS * BITS_PER_LONG)
#define DEF_CMD_PER_LUN SDEBUG_CANQUEUE
+#define SDEB_ORDER_TOO_LARGE 4096
/* UA - Unit Attention; SA - Service Action; SSU - Start Stop Unit */
#define F_D_IN 1 /* Data-in command (e.g. READ) */
@@ -318,8 +319,11 @@ struct sdebug_host_info {
/* There is an xarray of pointers to this struct's objects, one per host */
struct sdeb_store_info {
+ unsigned int n_elem; /* number of sgl elements */
+ unsigned int order; /* as used by alloc_pages() */
+ unsigned int elem_pow2; /* PAGE_SHIFT + order */
rwlock_t macc_lck; /* for atomic media access on this store */
- u8 *storep; /* user data storage (ram) */
+ struct scatterlist *sgl; /* main store: n_elem array of same sized allocs */
struct t10_pi_tuple *dif_storep; /* protection info */
void *map_storep; /* provisioning map */
};
@@ -880,19 +884,6 @@ static inline bool scsi_debug_lbp(void)
(sdebug_lbpu || sdebug_lbpws || sdebug_lbpws10);
}
-static void *lba2fake_store(struct sdeb_store_info *sip,
- unsigned long long lba)
-{
- struct sdeb_store_info *lsip = sip;
-
- lba = do_div(lba, sdebug_store_sectors);
- if (!sip || !sip->storep) {
- WARN_ON_ONCE(true);
- lsip = xa_load(per_store_ap, 0); /* should never be NULL */
- }
- return lsip->storep + lba * sdebug_sector_size;
-}
-
static struct t10_pi_tuple *dif_store(struct sdeb_store_info *sip,
sector_t sector)
{
@@ -1001,7 +992,6 @@ static int scsi_debug_ioctl(struct scsi_device *dev, unsigned int cmd,
__func__, cmd);
}
return -EINVAL;
- /* return -ENOTTY; // correct return but upsets fdisk */
}
static void config_cdb_len(struct scsi_device *sdev)
@@ -1221,6 +1211,55 @@ static int fetch_to_dev_buffer(struct scsi_cmnd *scp, unsigned char *arr,
return scsi_sg_copy_to_buffer(scp, arr, arr_len);
}
+static bool sdeb_sgl_cmp_buf(struct scatterlist *sgl, unsigned int nents,
+ const void *buf, size_t buflen, off_t skip)
+{
+ bool equ = true;
+ size_t offset = 0;
+ size_t len;
+ struct sg_mapping_iter miter;
+
+ if (buflen == 0)
+ return true;
+ sg_miter_start(&miter, sgl, nents, SG_MITER_ATOMIC | SG_MITER_FROM_SG);
+ if (!sg_miter_skip(&miter, skip))
+ goto fini;
+
+ while (equ && (offset < buflen) && sg_miter_next(&miter)) {
+ len = min(miter.length, buflen - offset);
+ equ = memcmp(buf + offset, miter.addr, len) == 0;
+ offset += len;
+ miter.consumed = len;
+ sg_miter_stop(&miter);
I think, the sg_miter_stop is obsolete here.
Also, I think there is no need to set miter.consumed. If len is less
than miter.length, the loop will end and not not call sg_miter_next
again.
Bodo
+ }
+fini:
+ sg_miter_stop(&miter);
+ return equ;
+}
+
