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Subject[PATCH] Mostly PAGE_SIZE IO for RAW (NEW VERSION)
Date
Hi,

Here is the new version of the patch for doing mostly PAGE_SIZE IO
for RAW (2.4.17). Here are the things that changed.

1) Inorder to address Jens Axboe and Ben LaHaise concerns, I followed
Andrea's suggestion and modified the patch to do variable size IO
only for the tested drivers/adaptors.

The patch will work only on the drivers which set "can_do_varyio"
bit in their SCSI Host template. Currently, I tested this on
QLOGIC, AIC adaptors. The hardware which has extra aligment
restrictions & drivers which can not handle variable buffer sizes
in a single IO can be safely excluded.

2) Limited the scope to only SCSI.


Thanks to Andrea, Jens, Ben & Alan for their valuable input.

Thanks,
Badari

diff -Nur -X dontdiff linux/drivers/block/ll_rw_blk.c linux-2417newvary/drivers/block/ll_rw_blk.c
--- linux/drivers/block/ll_rw_blk.c Mon Oct 29 12:11:17 2001
+++ linux-2417newvary/drivers/block/ll_rw_blk.c Fri Jan 11 16:58:37 2002
@@ -118,6 +118,13 @@
int * max_sectors[MAX_BLKDEV];

/*
+ * blkdev_varyio indicates if variable size IO can be done on a device.
+ *
+ * Currently used for doing variable size IO on RAW devices.
+ */
+char * blkdev_varyio[MAX_BLKDEV];
+
+/*
* How many reqeusts do we allocate per queue,
* and how many do we "batch" on freeing them?
*/
@@ -874,20 +881,7 @@
}


-/**
- * submit_bh: submit a buffer_head to the block device later for I/O
- * @rw: whether to %READ or %WRITE, or maybe to %READA (read ahead)
- * @bh: The &struct buffer_head which describes the I/O
- *
- * submit_bh() is very similar in purpose to generic_make_request(), and
- * uses that function to do most of the work.
- *
- * The extra functionality provided by submit_bh is to determine
- * b_rsector from b_blocknr and b_size, and to set b_rdev from b_dev.
- * This is is appropriate for IO requests that come from the buffer
- * cache and page cache which (currently) always use aligned blocks.
- */
-void submit_bh(int rw, struct buffer_head * bh)
+static inline void submit_bh_rsector(int rw, struct buffer_head * bh, int rsect)
{
int count = bh->b_size >> 9;

@@ -901,7 +895,7 @@
* further remap this.
*/
bh->b_rdev = bh->b_dev;
- bh->b_rsector = bh->b_blocknr * count;
+ bh->b_rsector = rsect;

generic_make_request(rw, bh);

@@ -913,6 +907,33 @@
kstat.pgpgin += count;
break;
}
+}
+
+/**
+ * submit_bh: submit a buffer_head to the block device later for I/O
+ * @rw: whether to %READ or %WRITE, or maybe to %READA (read ahead)
+ * @bh: The &struct buffer_head which describes the I/O
+ *
+ * submit_bh() is very similar in purpose to generic_make_request(), and
+ * uses that function to do most of the work.
+ *
+ * The extra functionality provided by submit_bh is to determine
+ * b_rsector from b_blocknr and b_size, and to set b_rdev from b_dev.
+ * This is is appropriate for IO requests that come from the buffer
+ * cache and page cache which (currently) always use aligned blocks.
+ */
+void submit_bh(int rw, struct buffer_head * bh)
+{
+ submit_bh_rsector(rw, bh, bh->b_blocknr * (bh->b_size >> 9));
+}
+
+/*
+ * submit_bh_blknr() - same as submit_bh() except that b_rsector is
+ * set to b_blocknr. Used for RAW VARY.
+ */
+void submit_bh_blknr(int rw, struct buffer_head * bh)
+{
+ submit_bh_rsector(rw, bh, bh->b_blocknr);
}

/**
diff -Nur -X dontdiff linux/drivers/char/raw.c linux-2417newvary/drivers/char/raw.c
--- linux/drivers/char/raw.c Sat Sep 22 20:35:43 2001
+++ linux-2417newvary/drivers/char/raw.c Fri Jan 11 21:37:16 2002
@@ -23,6 +23,7 @@
struct block_device *binding;
int inuse, sector_size, sector_bits;
struct semaphore mutex;
+ int can_do_vary;
} raw_device_data_t;

static raw_device_data_t raw_devices[256];
@@ -225,6 +226,8 @@
bdput(raw_devices[minor].binding);
raw_devices[minor].binding =
bdget(kdev_t_to_nr(MKDEV(rq.block_major, rq.block_minor)));
+ raw_devices[minor].can_do_vary =
+ get_blkdev_varyio(rq.block_major, rq.block_minor);
up(&raw_devices[minor].mutex);
} else {
struct block_device *bdev;
@@ -283,6 +286,7 @@

int sector_size, sector_bits, sector_mask;
int max_sectors;
+ int can_do_varyio;

/*
* First, a few checks on device size limits
@@ -308,6 +312,7 @@
sector_bits = raw_devices[minor].sector_bits;
sector_mask = sector_size- 1;
max_sectors = KIO_MAX_SECTORS >> (sector_bits - 9);
+ can_do_varyio = raw_devices[minor].can_do_vary;

if (blk_size[MAJOR(dev)])
limit = (((loff_t) blk_size[MAJOR(dev)][MINOR(dev)]) << BLOCK_SIZE_BITS) >> sector_bits;
@@ -350,8 +355,12 @@

for (i=0; i < blocks; i++)
iobuf->blocks[i] = blocknr++;
+
+ iobuf->dovary = can_do_varyio;

err = brw_kiovec(rw, 1, &iobuf, dev, iobuf->blocks, sector_size);
+
+ iobuf->dovary = 0;

if (rw == READ && err > 0)
mark_dirty_kiobuf(iobuf, err);
diff -Nur -X dontdiff linux/drivers/scsi/aic7xxx/aic7xxx_linux_host.h linux-2417newvary/drivers/scsi/aic7xxx/aic7xxx_linux_host.h
--- linux/drivers/scsi/aic7xxx/aic7xxx_linux_host.h Thu Oct 25 13:53:49 2001
+++ linux-2417newvary/drivers/scsi/aic7xxx/aic7xxx_linux_host.h Fri Jan 11 21:39:18 2002
@@ -89,7 +89,8 @@
present: 0, /* number of 7xxx's present */\
unchecked_isa_dma: 0, /* no memory DMA restrictions */\
use_clustering: ENABLE_CLUSTERING, \
- use_new_eh_code: 1 \
+ use_new_eh_code: 1, \
+ can_do_varyio: 1 \
}

#endif /* _AIC7XXX_LINUX_HOST_H_ */
diff -Nur -X dontdiff linux/drivers/scsi/hosts.h linux-2417newvary/drivers/scsi/hosts.h
--- linux/drivers/scsi/hosts.h Thu Nov 22 11:49:15 2001
+++ linux-2417newvary/drivers/scsi/hosts.h Fri Jan 11 18:19:39 2002
@@ -292,6 +292,11 @@
unsigned emulated:1;

/*
+ * True for drivers which can handle variable length IO
+ */
+ unsigned can_do_varyio:1;
+
+ /*
* Name of proc directory
*/
char *proc_name;
diff -Nur -X dontdiff linux/drivers/scsi/qlogicisp.h linux-2417newvary/drivers/scsi/qlogicisp.h
--- linux/drivers/scsi/qlogicisp.h Fri Nov 12 04:40:46 1999
+++ linux-2417newvary/drivers/scsi/qlogicisp.h Thu Jan 10 22:51:55 2002
@@ -84,7 +84,8 @@
cmd_per_lun: 1, \
present: 0, \
unchecked_isa_dma: 0, \
- use_clustering: DISABLE_CLUSTERING \
+ use_clustering: DISABLE_CLUSTERING, \
+ can_do_varyio: 1 \
}

#endif /* _QLOGICISP_H */
diff -Nur -X dontdiff linux/drivers/scsi/sd.c linux-2417newvary/drivers/scsi/sd.c
--- linux/drivers/scsi/sd.c Fri Nov 9 14:05:06 2001
+++ linux-2417newvary/drivers/scsi/sd.c Fri Jan 11 21:34:19 2002
@@ -1241,6 +1241,8 @@
return 1;
}

+#define SD_DISK_MAJOR(i) SD_MAJOR((i) >> 4)
+
static int sd_attach(Scsi_Device * SDp)
{
unsigned int devnum;
@@ -1274,6 +1276,22 @@
printk("Attached scsi %sdisk %s at scsi%d, channel %d, id %d, lun %d\n",
SDp->removable ? "removable " : "",
nbuff, SDp->host->host_no, SDp->channel, SDp->id, SDp->lun);
+
+ if (SDp->host->hostt->can_do_varyio) {
+ char *varyio;
+
+ varyio = blkdev_varyio[SD_DISK_MAJOR(i)];
+ if (varyio == NULL) {
+ varyio = kmalloc((sd_template.dev_max << 4), GFP_ATOMIC);
+ if (varyio == NULL) {
+ printk("Unable allocate for VARYIO\n");
+ return 0;
+ }
+ blkdev_varyio[SD_DISK_MAJOR(i)] = varyio;
+ }
+
+ memset(varyio + (devnum << 4), 1, 16);
+ }
return 0;
}

diff -Nur -X dontdiff linux/fs/buffer.c linux-2417newvary/fs/buffer.c
--- linux/fs/buffer.c Fri Jan 11 18:11:37 2002
+++ linux-2417newvary/fs/buffer.c Fri Jan 11 18:16:29 2002
@@ -2071,11 +2071,11 @@
err = 0;

for (i = nr; --i >= 0; ) {
- iosize += size;
tmp = bh[i];
if (buffer_locked(tmp)) {
wait_on_buffer(tmp);
}
+ iosize += tmp->b_size;

if (!buffer_uptodate(tmp)) {
/* We are traversing bh'es in reverse order so
@@ -2118,6 +2118,7 @@
struct kiobuf * iobuf = NULL;
struct page * map;
struct buffer_head *tmp, **bhs = NULL;
+ int iosize = size;

if (!nr)
return 0;
@@ -2154,7 +2155,7 @@
}

while (length > 0) {
- blocknr = b[bufind++];
+ blocknr = b[bufind];
if (blocknr == -1UL) {
if (rw == READ) {
/* there was an hole in the filesystem */
@@ -2167,9 +2168,15 @@
} else
BUG();
}
+ if (iobuf->dovary) {
+ iosize = PAGE_SIZE - offset;
+ if (iosize > length)
+ iosize = length;
+ }
+ bufind += (iosize/size);
tmp = bhs[bhind++];

- tmp->b_size = size;
+ tmp->b_size = iosize;
set_bh_page(tmp, map, offset);
tmp->b_this_page = tmp;

@@ -2185,7 +2192,10 @@
set_bit(BH_Uptodate, &tmp->b_state);

atomic_inc(&iobuf->io_count);
- submit_bh(rw, tmp);
+ if (iobuf->dovary)
+ submit_bh_blknr(rw, tmp);
+ else
+ submit_bh(rw, tmp);
/*
* Wait for IO if we have got too much
*/
@@ -2200,8 +2210,8 @@
}

skip_block:
- length -= size;
- offset += size;
+ length -= iosize;
+ offset += iosize;

if (offset >= PAGE_SIZE) {
offset = 0;
diff -Nur -X dontdiff linux/include/linux/blkdev.h linux-2417newvary/include/linux/blkdev.h
--- linux/include/linux/blkdev.h Mon Nov 26 05:29:17 2001
+++ linux-2417newvary/include/linux/blkdev.h Fri Jan 11 16:58:52 2002
@@ -175,6 +175,8 @@

extern int * max_segments[MAX_BLKDEV];

+extern char * blkdev_varyio[MAX_BLKDEV];
+
#define MAX_SEGMENTS 128
#define MAX_SECTORS 255

@@ -228,4 +230,12 @@
return retval;
}

+static inline int get_blkdev_varyio(int major, int minor)
+{
+ int retval = 0;
+ if (blkdev_varyio[major]) {
+ retval = blkdev_varyio[major][minor];
+ }
+ return retval;
+}
#endif
diff -Nur -X dontdiff linux/include/linux/iobuf.h linux-2417newvary/include/linux/iobuf.h
--- linux/include/linux/iobuf.h Thu Nov 22 11:46:26 2001
+++ linux-2417newvary/include/linux/iobuf.h Wed Jan 9 22:17:39 2002
@@ -44,7 +44,8 @@

struct page ** maplist;

- unsigned int locked : 1; /* If set, pages has been locked */
+ unsigned int locked : 1, /* If set, pages has been locked */
+ dovary : 1; /* If set, do variable size IO */

/* Always embed enough struct pages for atomic IO */
struct page * map_array[KIO_STATIC_PAGES];
-
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