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SUNRPC: Add an xdr_align_data() function

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For now, this function simply aligns the data at the beginning of the
pages. This can eventually be expanded to shift data to the correct
offsets when we're ready.

Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
This commit is contained in:
Anna Schumaker 2020-04-21 11:27:00 -04:00
parent c05eafad6b
commit e6ac0accb2
2 changed files with 122 additions and 0 deletions
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1
include/linux/sunrpc/xdr.h
View File

@ -250,6 +250,7 @@ extern __be32 *xdr_inline_decode(struct xdr_stream *xdr, size_t nbytes);
extern unsigned int xdr_read_pages(struct xdr_stream *xdr, unsigned int len);
extern void xdr_enter_page(struct xdr_stream *xdr, unsigned int len);
extern int xdr_process_buf(struct xdr_buf *buf, unsigned int offset, unsigned int len, int (*actor)(struct scatterlist *, void *), void *data);
extern uint64_t xdr_align_data(struct xdr_stream *, uint64_t, uint32_t);
extern uint64_t xdr_expand_hole(struct xdr_stream *, uint64_t, uint64_t);
/**

121
net/sunrpc/xdr.c
View File

@ -19,6 +19,9 @@
#include <linux/bvec.h>
#include <trace/events/sunrpc.h>
static void _copy_to_pages(struct page **, size_t, const char *, size_t);
/*
* XDR functions for basic NFS types
*/
@ -201,6 +204,88 @@ EXPORT_SYMBOL_GPL(xdr_inline_pages);
* Helper routines for doing 'memmove' like operations on a struct xdr_buf
*/
/**
* _shift_data_left_pages
* @pages: vector of pages containing both the source and dest memory area.
* @pgto_base: page vector address of destination
* @pgfrom_base: page vector address of source
* @len: number of bytes to copy
*
* Note: the addresses pgto_base and pgfrom_base are both calculated in
* the same way:
* if a memory area starts at byte 'base' in page 'pages[i]',
* then its address is given as (i << PAGE_CACHE_SHIFT) + base
* Alse note: pgto_base must be < pgfrom_base, but the memory areas
* they point to may overlap.
*/
static void
_shift_data_left_pages(struct page **pages, size_t pgto_base,
size_t pgfrom_base, size_t len)
{
struct page **pgfrom, **pgto;
char *vfrom, *vto;
size_t copy;
BUG_ON(pgfrom_base <= pgto_base);
pgto = pages + (pgto_base >> PAGE_SHIFT);
pgfrom = pages + (pgfrom_base >> PAGE_SHIFT);
pgto_base &= ~PAGE_MASK;
pgfrom_base &= ~PAGE_MASK;
do {
if (pgto_base >= PAGE_SIZE) {
pgto_base = 0;
pgto++;
}
if (pgfrom_base >= PAGE_SIZE){
pgfrom_base = 0;
pgfrom++;
}
copy = len;
if (copy > (PAGE_SIZE - pgto_base))
copy = PAGE_SIZE - pgto_base;
if (copy > (PAGE_SIZE - pgfrom_base))
copy = PAGE_SIZE - pgfrom_base;
vto = kmap_atomic(*pgto);
if (*pgto != *pgfrom) {
vfrom = kmap_atomic(*pgfrom);
memcpy(vto + pgto_base, vfrom + pgfrom_base, copy);
kunmap_atomic(vfrom);
} else
memmove(vto + pgto_base, vto + pgfrom_base, copy);
flush_dcache_page(*pgto);
kunmap_atomic(vto);
pgto_base += copy;
pgfrom_base += copy;
} while ((len -= copy) != 0);
}
static void
_shift_data_left_tail(struct xdr_buf *buf, unsigned int pgto, size_t len)
{
struct kvec *tail = buf->tail;
if (len > tail->iov_len)
len = tail->iov_len;
_copy_to_pages(buf->pages,
buf->page_base + pgto,
(char *)tail->iov_base,
len);
tail->iov_len -= len;
if (tail->iov_len > 0)
memmove((char *)tail->iov_base,
tail->iov_base + len,
tail->iov_len);
}
/**
* _shift_data_right_pages
* @pages: vector of pages containing both the source and dest memory area.
@ -1128,6 +1213,42 @@ unsigned int xdr_read_pages(struct xdr_stream *xdr, unsigned int len)
}
EXPORT_SYMBOL_GPL(xdr_read_pages);
uint64_t xdr_align_data(struct xdr_stream *xdr, uint64_t offset, uint32_t length)
{
struct xdr_buf *buf = xdr->buf;
unsigned int from, bytes;
unsigned int shift = 0;
if ((offset + length) < offset ||
(offset + length) > buf->page_len)
length = buf->page_len - offset;
xdr_realign_pages(xdr);
from = xdr_page_pos(xdr);
bytes = xdr->nwords << 2;
if (length < bytes)
bytes = length;
/* Move page data to the left */
if (from > offset) {
shift = min_t(unsigned int, bytes, buf->page_len - from);
_shift_data_left_pages(buf->pages,
buf->page_base + offset,
buf->page_base + from,
shift);
bytes -= shift;
/* Move tail data into the pages, if necessary */
if (bytes > 0)
_shift_data_left_tail(buf, offset + shift, bytes);
}
xdr->nwords -= XDR_QUADLEN(length);
xdr_set_page(xdr, from + length, PAGE_SIZE);
return length;
}
EXPORT_SYMBOL_GPL(xdr_align_data);
uint64_t xdr_expand_hole(struct xdr_stream *xdr, uint64_t offset, uint64_t length)
{
struct xdr_buf *buf = xdr->buf;