[SCSI] sg: fixes for large page_size
This sg driver patch addresses the problem with larger
page sizes reported by Brian King in this post:
http://marc.theaimsgroup.com/?l=linux-scsi&m=115867718623631&w=2
Some other related matters are also addressed. Some of these
prevent oopses when the SG_SCATTER_SZ or scatter_elem_sz are
set to inappropriate values.
The scatter_elem_sz has been tested up to 4 MB which should
make the largest data transfer with one SCSI command, 32 MB
less one block, achievable with a relatively small number
of elements in the scatter gather list.
ChangeLog:
- add scatter_elem_sz boot time parameter and sysfs module
parameter that is initialized to SG_SCATTER_SZ
- the driver will then adjust scatter_elem_sz to be the
max(given(scatter_elem_sz), PAGE_SIZE)
It will also round it up, if necessary, to be a power
of two
- clean up sg.h header, correct bad urls and some statements
that are no longer valid
- make the def_reserved_size sysfs module attribute writable
Signed-off-by: Douglas Gilbert <dougg@torque.net>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 34f9343e..3f8b931 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -60,7 +60,7 @@
#ifdef CONFIG_SCSI_PROC_FS
#include <linux/proc_fs.h>
-static char *sg_version_date = "20060818";
+static char *sg_version_date = "20060920";
static int sg_proc_init(void);
static void sg_proc_cleanup(void);
@@ -94,6 +94,9 @@
static int def_reserved_size = -1; /* picks up init parameter */
static int sg_allow_dio = SG_ALLOW_DIO_DEF;
+static int scatter_elem_sz = SG_SCATTER_SZ;
+static int scatter_elem_sz_prev = SG_SCATTER_SZ;
+
#define SG_SECTOR_SZ 512
#define SG_SECTOR_MSK (SG_SECTOR_SZ - 1)
@@ -1537,11 +1540,9 @@
msleep(10); /* dirty detach so delay device destruction */
}
-/* Set 'perm' (4th argument) to 0 to disable module_param's definition
- * of sysfs parameters (which module_param doesn't yet support).
- * Sysfs parameters defined explicitly below.
- */
-module_param_named(def_reserved_size, def_reserved_size, int, S_IRUGO);
+module_param_named(scatter_elem_sz, scatter_elem_sz, int, S_IRUGO | S_IWUSR);
+module_param_named(def_reserved_size, def_reserved_size, int,
+ S_IRUGO | S_IWUSR);
module_param_named(allow_dio, sg_allow_dio, int, S_IRUGO | S_IWUSR);
MODULE_AUTHOR("Douglas Gilbert");
@@ -1550,6 +1551,8 @@
MODULE_VERSION(SG_VERSION_STR);
MODULE_ALIAS_CHARDEV_MAJOR(SCSI_GENERIC_MAJOR);
+MODULE_PARM_DESC(scatter_elem_sz, "scatter gather element "
+ "size (default: max(SG_SCATTER_SZ, PAGE_SIZE))");
MODULE_PARM_DESC(def_reserved_size, "size of buffer reserved for each fd");
MODULE_PARM_DESC(allow_dio, "allow direct I/O (default: 0 (disallow))");
@@ -1558,8 +1561,14 @@
{
int rc;
+ if (scatter_elem_sz < PAGE_SIZE) {
+ scatter_elem_sz = PAGE_SIZE;
+ scatter_elem_sz_prev = scatter_elem_sz;
+ }
if (def_reserved_size >= 0)
sg_big_buff = def_reserved_size;
+ else
+ def_reserved_size = sg_big_buff;
rc = register_chrdev_region(MKDEV(SCSI_GENERIC_MAJOR, 0),
SG_MAX_DEVS, "sg");
@@ -1842,15 +1851,30 @@
if (mx_sc_elems < 0)
return mx_sc_elems; /* most likely -ENOMEM */
+ num = scatter_elem_sz;
+ if (unlikely(num != scatter_elem_sz_prev)) {
+ if (num < PAGE_SIZE) {
+ scatter_elem_sz = PAGE_SIZE;
+ scatter_elem_sz_prev = PAGE_SIZE;
+ } else
+ scatter_elem_sz_prev = num;
+ }
for (k = 0, sg = schp->buffer, rem_sz = blk_size;
(rem_sz > 0) && (k < mx_sc_elems);
++k, rem_sz -= ret_sz, ++sg) {
- num = (rem_sz > SG_SCATTER_SZ) ? SG_SCATTER_SZ : rem_sz;
+ num = (rem_sz > scatter_elem_sz_prev) ?
+ scatter_elem_sz_prev : rem_sz;
p = sg_page_malloc(num, sfp->low_dma, &ret_sz);
if (!p)
return -ENOMEM;
+ if (num == scatter_elem_sz_prev) {
+ if (unlikely(ret_sz > scatter_elem_sz_prev)) {
+ scatter_elem_sz = ret_sz;
+ scatter_elem_sz_prev = ret_sz;
+ }
+ }
sg->page = p;
sg->length = ret_sz;
@@ -2341,6 +2365,9 @@
}
write_unlock_irqrestore(&sg_dev_arr_lock, iflags);
SCSI_LOG_TIMEOUT(3, printk("sg_add_sfp: sfp=0x%p\n", sfp));
+ if (unlikely(sg_big_buff != def_reserved_size))
+ sg_big_buff = def_reserved_size;
+
sg_build_reserve(sfp, sg_big_buff);
SCSI_LOG_TIMEOUT(3, printk("sg_add_sfp: bufflen=%d, k_use_sg=%d\n",
sfp->reserve.bufflen, sfp->reserve.k_use_sg));
@@ -2437,16 +2464,16 @@
return srp ? 1 : 0;
}
-/* If retSzp==NULL want exact size or fail */
+/* The size fetched (value output via retSzp) set when non-NULL return */
static struct page *
sg_page_malloc(int rqSz, int lowDma, int *retSzp)
{
struct page *resp = NULL;
gfp_t page_mask;
int order, a_size;
- int resSz = rqSz;
+ int resSz;
- if (rqSz <= 0)
+ if ((rqSz <= 0) || (NULL == retSzp))
return resp;
if (lowDma)
@@ -2456,8 +2483,9 @@
for (order = 0, a_size = PAGE_SIZE; a_size < rqSz;
order++, a_size <<= 1) ;
+ resSz = a_size; /* rounded up if necessary */
resp = alloc_pages(page_mask, order);
- while ((!resp) && order && retSzp) {
+ while ((!resp) && order) {
--order;
a_size >>= 1; /* divide by 2, until PAGE_SIZE */
resp = alloc_pages(page_mask, order); /* try half */
@@ -2466,8 +2494,7 @@
if (resp) {
if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SYS_RAWIO))
memset(page_address(resp), 0, resSz);
- if (retSzp)
- *retSzp = resSz;
+ *retSzp = resSz;
}
return resp;
}