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| Kernel Functions for Drivers | bioclone(9F) |
| | bioclone - clone another buffer |
SYNOPSIS
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#include <sys/ddi.h> #include <sys/sunddi.h>
struct buf *bioclone(struct buf *bp, off_t off, size_t len, dev_t dev, daddr_t blkno, int (*iodone) (struct buf *), struct buf *bp_mem, int sleepflag); |
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Solaris DDI specific (Solaris DDI).
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bp
- Pointer to the buf(9S) structure describing the original I/O request.
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off
- Offset within original I/O request
where new I/O request should start.
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len
- Length of the I/O request.
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dev
- Device number.
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blkno
- Block number on device.
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iodone
- Specific biodone(9F) routine.
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bp_mem
- Pointer to a buffer structure to be filled in or NULL.
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sleepflag
- Determines whether caller can sleep for memory. Possible
flags are KM_SLEEP to allow sleeping until memory is
available, or KM_NOSLEEP to return NULL immediately if memory is not available.
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bioclone() returns an initialized buffer to perform I/O to a portion of another buffer. The new buffer
will be set up to perform I/O to the range
within the original I/O request specified
by the parameters off and len.
An offset 0 starts the new I/O request
at the same address as the original request. off
+ len must not exceed b_bcount,
the length of the original request. The device number dev
specifies the device to which the buffer is to perform I/O. blkno is the block number on device.
It will be assigned to the b_blkno field of the
cloned buffer structure. iodone lets the driver
identify a specific biodone(9F) routine
to be called by the driver when the I/O is
complete. bp_mem determines from where the space
for the buffer should be allocated. If bp_mem is NULL, bioclone() will allocate
a new buffer using getrbuf(9F).
If sleepflag is set to KM_SLEEP,
the driver may sleep until space is freed up. If sleepflag
is set to KM_NOSLEEP, the driver will not sleep. In either
case, a pointer to the allocated space is returned or NULL to indicate that no space was available. After the transfer
is completed, the buffer has to be freed using freerbuf(9F).
If bp_mem is not NULL,
it will be used as the space for the buffer structure. The driver has to
ensure that bp_mem is initialized properly either
using getrbuf(9F) or bioinit(9F).
If the original buffer is mapped into the kernel virtual address space
using bp_mapin(9F) before calling bp_clone(), a clone buffer will share the kernel mapping of the
original buffer. An additional bp_mapin() to get a kernel
mapping for the clone buffer is not necessary.
The driver has to ensure that the original buffer is not freed while
any of the clone buffers is still performing I/O. The biodone() function has to be called on
all clone buffers before it is called on the original
buffer.
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The bioclone() function returns a pointer to the
initialized buffer header, or NULL if no space
is available.
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bioclone() can be called from user or interrupt
context. Drivers must not allow bioclone() to sleep if
called from an interrupt routine.
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| | Example 1. : Using bioclone
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A device driver can use bioclone() for disk striping.
For each disk in the stripe, a clone buffer is created which performs I/O to a portion of the original buffer.
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static int
stripe_strategy(struct buf *bp)
{
...
bp_orig = bp;
bp_1 = bioclone(bp_orig, 0, size_1, dev_1, blkno_1,
stripe_done, NULL, KM_SLEEP);
fragment++;
...
bp_n = bioclone(bp_orig, offset_n, size_n, dev_n,
blkno_n, stripe_done, NULL, KM_SLEEP);
fragment++;
/* submit bp_1 ... bp_n to device */
xxstrategy(bp_x);
return (0);
}
static uint_t
xxintr(caddr_t arg)
{
...
/*
* get bp of completed subrequest. biodone(9F) will
* call stripe_done()
*/
biodone(bp);
return (0);
}
static int
stripe_done(struct buf *bp)
{
...
freerbuf(bp);
fragment--;
if (fragment == 0) {
/* get bp_orig */
biodone(bp_orig);
}
return (0);
}
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