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[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round it up, if necessary, to be a power of two - clean up sg.h header, correct bad urls and some statements that are no longer valid - make the def_reserved_size sysfs module attribute writable Signed-off-by: Douglas Gilbert 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>
This commit is contained in:
Douglas Gilbert
James Bottomley
parent
8aee918a1c
commit
6460e75a10
@ -60,7 +60,7 @@ static int sg_version_num = 30534; /* 2 digits for each component */
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#ifdef CONFIG_SCSI_PROC_FS
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#include <linux/proc_fs.h>
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static char *sg_version_date = "20060818";
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static char *sg_version_date = "20060920";
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static int sg_proc_init(void);
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static void sg_proc_cleanup(void);
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@ -94,6 +94,9 @@ int sg_big_buff = SG_DEF_RESERVED_SIZE;
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static int def_reserved_size = -1; /* picks up init parameter */
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static int sg_allow_dio = SG_ALLOW_DIO_DEF;
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static int scatter_elem_sz = SG_SCATTER_SZ;
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static int scatter_elem_sz_prev = SG_SCATTER_SZ;
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#define SG_SECTOR_SZ 512
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#define SG_SECTOR_MSK (SG_SECTOR_SZ - 1)
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@ -1537,11 +1540,9 @@ sg_remove(struct class_device *cl_dev, struct class_interface *cl_intf)
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msleep(10); /* dirty detach so delay device destruction */
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}
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/* Set 'perm' (4th argument) to 0 to disable module_param's definition
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* of sysfs parameters (which module_param doesn't yet support).
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* Sysfs parameters defined explicitly below.
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*/
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module_param_named(def_reserved_size, def_reserved_size, int, S_IRUGO);
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module_param_named(scatter_elem_sz, scatter_elem_sz, int, S_IRUGO | S_IWUSR);
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module_param_named(def_reserved_size, def_reserved_size, int,
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S_IRUGO | S_IWUSR);
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module_param_named(allow_dio, sg_allow_dio, int, S_IRUGO | S_IWUSR);
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MODULE_AUTHOR("Douglas Gilbert");
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@ -1550,6 +1551,8 @@ MODULE_LICENSE("GPL");
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MODULE_VERSION(SG_VERSION_STR);
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MODULE_ALIAS_CHARDEV_MAJOR(SCSI_GENERIC_MAJOR);
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MODULE_PARM_DESC(scatter_elem_sz, "scatter gather element "
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"size (default: max(SG_SCATTER_SZ, PAGE_SIZE))");
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MODULE_PARM_DESC(def_reserved_size, "size of buffer reserved for each fd");
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MODULE_PARM_DESC(allow_dio, "allow direct I/O (default: 0 (disallow))");
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@ -1558,8 +1561,14 @@ init_sg(void)
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{
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int rc;
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if (scatter_elem_sz < PAGE_SIZE) {
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scatter_elem_sz = PAGE_SIZE;
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scatter_elem_sz_prev = scatter_elem_sz;
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}
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if (def_reserved_size >= 0)
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sg_big_buff = def_reserved_size;
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else
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def_reserved_size = sg_big_buff;
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rc = register_chrdev_region(MKDEV(SCSI_GENERIC_MAJOR, 0),
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SG_MAX_DEVS, "sg");
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@ -1842,15 +1851,30 @@ sg_build_indirect(Sg_scatter_hold * schp, Sg_fd * sfp, int buff_size)
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if (mx_sc_elems < 0)
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return mx_sc_elems; /* most likely -ENOMEM */
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num = scatter_elem_sz;
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if (unlikely(num != scatter_elem_sz_prev)) {
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if (num < PAGE_SIZE) {
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scatter_elem_sz = PAGE_SIZE;
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scatter_elem_sz_prev = PAGE_SIZE;
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} else
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scatter_elem_sz_prev = num;
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}
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for (k = 0, sg = schp->buffer, rem_sz = blk_size;
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(rem_sz > 0) && (k < mx_sc_elems);
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++k, rem_sz -= ret_sz, ++sg) {
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num = (rem_sz > SG_SCATTER_SZ) ? SG_SCATTER_SZ : rem_sz;
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num = (rem_sz > scatter_elem_sz_prev) ?
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scatter_elem_sz_prev : rem_sz;
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p = sg_page_malloc(num, sfp->low_dma, &ret_sz);
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if (!p)
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return -ENOMEM;
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if (num == scatter_elem_sz_prev) {
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if (unlikely(ret_sz > scatter_elem_sz_prev)) {
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scatter_elem_sz = ret_sz;
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scatter_elem_sz_prev = ret_sz;
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}
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}
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sg->page = p;
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sg->length = ret_sz;
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@ -2341,6 +2365,9 @@ sg_add_sfp(Sg_device * sdp, int dev)
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}
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write_unlock_irqrestore(&sg_dev_arr_lock, iflags);
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SCSI_LOG_TIMEOUT(3, printk("sg_add_sfp: sfp=0x%p\n", sfp));
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if (unlikely(sg_big_buff != def_reserved_size))
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sg_big_buff = def_reserved_size;
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sg_build_reserve(sfp, sg_big_buff);
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SCSI_LOG_TIMEOUT(3, printk("sg_add_sfp: bufflen=%d, k_use_sg=%d\n",
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sfp->reserve.bufflen, sfp->reserve.k_use_sg));
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@ -2437,16 +2464,16 @@ sg_res_in_use(Sg_fd * sfp)
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return srp ? 1 : 0;
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}
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/* If retSzp==NULL want exact size or fail */
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/* The size fetched (value output via retSzp) set when non-NULL return */
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static struct page *
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sg_page_malloc(int rqSz, int lowDma, int *retSzp)
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{
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struct page *resp = NULL;
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gfp_t page_mask;
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int order, a_size;
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int resSz = rqSz;
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int resSz;
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if (rqSz <= 0)
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if ((rqSz <= 0) || (NULL == retSzp))
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return resp;
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if (lowDma)
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@ -2456,8 +2483,9 @@ sg_page_malloc(int rqSz, int lowDma, int *retSzp)
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for (order = 0, a_size = PAGE_SIZE; a_size < rqSz;
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order++, a_size <<= 1) ;
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resSz = a_size; /* rounded up if necessary */
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resp = alloc_pages(page_mask, order);
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while ((!resp) && order && retSzp) {
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while ((!resp) && order) {
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--order;
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a_size >>= 1; /* divide by 2, until PAGE_SIZE */
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resp = alloc_pages(page_mask, order); /* try half */
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@ -2466,8 +2494,7 @@ sg_page_malloc(int rqSz, int lowDma, int *retSzp)
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if (resp) {
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if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SYS_RAWIO))
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memset(page_address(resp), 0, resSz);
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if (retSzp)
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*retSzp = resSz;
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*retSzp = resSz;
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}
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return resp;
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}
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@ -11,26 +11,10 @@
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Original driver (sg.h):
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* Copyright (C) 1992 Lawrence Foard
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Version 2 and 3 extensions to driver:
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* Copyright (C) 1998 - 2003 Douglas Gilbert
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* Copyright (C) 1998 - 2006 Douglas Gilbert
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Version: 3.5.29 (20030529)
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This version is for 2.5 series kernels.
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Changes since 3.5.28 (20030308)
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- fix bug introduced in version 3.1.24 (last segment of sgat list)
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Changes since 3.5.27 (20020812)
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- remove procfs entries: hosts, host_hdr + host_strs (now in sysfs)
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- add sysfs sg driver params: def_reserved_size, allow_dio, version
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- new boot option: "sg_allow_dio" and module parameter: "allow_dio"
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- multiple internal changes due to scsi subsystem rework
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Changes since 3.5.26 (20020708)
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- re-add direct IO using Kai Makisara's work
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- re-tab to 8, start using C99-isms
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- simplify memory management
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Changes since 3.5.25 (20020504)
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- driverfs additions
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- copy_to/from_user() fixes [William Stinson]
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- disable kiobufs support
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Version: 3.5.34 (20060920)
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This version is for 2.6 series kernels.
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For a full changelog see http://www.torque.net/sg
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@ -40,7 +24,7 @@ Map of SG verions to the Linux kernels in which they appear:
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2.1.40 2.2.20
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3.0.x optional version 3 sg driver for 2.2 series
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3.1.17++ 2.4.0++
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3.5.23++ 2.5.0++
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3.5.30++ 2.6.0++
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Major new features in SG 3.x driver (cf SG 2.x drivers)
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- SG_IO ioctl() combines function if write() and read()
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@ -51,14 +35,15 @@ Major new features in SG 3.x driver (cf SG 2.x drivers)
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data into kernel buffers and then use the CPU to copy the data into the
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user space (vice versa for writes). That is called "indirect" IO due to
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the double handling of data. There are two methods offered to remove the
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redundant copy: 1) direct IO which uses the kernel kiobuf mechanism and
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2) using the mmap() system call to map the reserve buffer (this driver has
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one reserve buffer per fd) into the user space. Both have their advantages.
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redundant copy: 1) direct IO and 2) using the mmap() system call to map
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the reserve buffer (this driver has one reserve buffer per fd) into the
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user space. Both have their advantages.
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In terms of absolute speed mmap() is faster. If speed is not a concern,
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indirect IO should be fine. Read the documentation for more information.
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** N.B. To use direct IO 'echo 1 > /proc/scsi/sg/allow_dio' may be
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needed. That pseudo file's content is defaulted to 0. **
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** N.B. To use direct IO 'echo 1 > /proc/scsi/sg/allow_dio' or
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'echo 1 > /sys/module/sg/parameters/allow_dio' is needed.
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That attribute is 0 by default. **
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Historical note: this SCSI pass-through driver has been known as "sg" for
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a decade. In broader kernel discussions "sg" is used to refer to scatter
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@ -72,20 +57,17 @@ Major new features in SG 3.x driver (cf SG 2.x drivers)
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http://www.torque.net/sg/p/sg_v3_ho.html
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This is a rendering from DocBook source [change the extension to "sgml"
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or "xml"]. There are renderings in "ps", "pdf", "rtf" and "txt" (soon).
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The SG_IO ioctl is now found in other parts kernel (e.g. the block layer).
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For more information see http://www.torque.net/sg/sg_io.html
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The older, version 2 documents discuss the original sg interface in detail:
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http://www.torque.net/sg/p/scsi-generic.txt
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http://www.torque.net/sg/p/scsi-generic_long.txt
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A version of this document (potentially out of date) may also be found in
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the kernel source tree, probably at:
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Documentation/scsi/scsi-generic.txt .
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Also available: <kernel_source>/Documentation/scsi/scsi-generic.txt
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Utility and test programs are available at the sg web site. They are
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bundled as sg_utils (for the lk 2.2 series) and sg3_utils (for the
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lk 2.4 series).
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There is a HOWTO on the Linux SCSI subsystem in the lk 2.4 series at:
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http://www.linuxdoc.org/HOWTO/SCSI-2.4-HOWTO
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packaged as sg3_utils (for the lk 2.4 and 2.6 series) and sg_utils
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(for the lk 2.2 series).
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*/
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@ -238,13 +220,12 @@ typedef struct sg_req_info { /* used by SG_GET_REQUEST_TABLE ioctl() */
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#define SG_GET_ACCESS_COUNT 0x2289
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#define SG_SCATTER_SZ (8 * 4096) /* PAGE_SIZE not available to user */
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#define SG_SCATTER_SZ (8 * 4096)
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/* Largest size (in bytes) a single scatter-gather list element can have.
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The value must be a power of 2 and <= (PAGE_SIZE * 32) [131072 bytes on
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i386]. The minimum value is PAGE_SIZE. If scatter-gather not supported
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by adapter then this value is the largest data block that can be
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read/written by a single scsi command. The user can find the value of
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PAGE_SIZE by calling getpagesize() defined in unistd.h . */
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The value used by the driver is 'max(SG_SCATTER_SZ, PAGE_SIZE)'.
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This value should be a power of 2 (and may be rounded up internally).
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If scatter-gather is not supported by adapter then this value is the
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largest data block that can be read/written by a single scsi command. */
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#define SG_DEFAULT_RETRIES 0
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