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libceph: isolate kmap() call in write_partial_msg_pages() 

In write_partial_msg_pages(), every case now does an identical call
to kmap(page).  Instead, just call it once inside the CRC-computing
block where it's needed.  Move the definition of kaddr inside that
block, and make it a (char *) to ensure portable pointer arithmetic.

We still don't kunmap() it until after the sendpage() call, in case
that also ends up needing to use the mapping.

Signed-off-by: Alex Elder <elder@dreamhost.com>
Reviewed-by: Sage Weil <sage@newdream.net>
This commit is contained in:
Alex Elder 2012-03-07 11:40:08 -06:00
parent 9bd1966344
commit 8d63e318c4
1 changed files with 2 additions and 11 deletions
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13
net/ceph/messenger.c
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@ -835,7 +835,6 @@ static int write_partial_msg_pages(struct ceph_connection *con)
while (data_len > con->out_msg_pos.data_pos) {
struct page *page = NULL;
void *kaddr = NULL;
int max_write = PAGE_SIZE;
int bio_offset = 0;
@ -856,18 +855,12 @@ static int write_partial_msg_pages(struct ceph_connection *con)
page = list_first_entry(&msg->trail->head,
struct page, lru);
if (do_datacrc)
kaddr = kmap(page);
max_write = PAGE_SIZE;
} else if (msg->pages) {
page = msg->pages[con->out_msg_pos.page];
if (do_datacrc)
kaddr = kmap(page);
} else if (msg->pagelist) {
page = list_first_entry(&msg->pagelist->head,
struct page, lru);
if (do_datacrc)
kaddr = kmap(page);
#ifdef CONFIG_BLOCK
} else if (msg->bio) {
struct bio_vec *bv;
@ -875,14 +868,10 @@ static int write_partial_msg_pages(struct ceph_connection *con)
bv = bio_iovec_idx(msg->bio_iter, msg->bio_seg);
page = bv->bv_page;
bio_offset = bv->bv_offset;
if (do_datacrc)
kaddr = kmap(page);
max_write = bv->bv_len;
#endif
} else {
page = zero_page;
if (do_datacrc)
kaddr = kmap(page);
}
len = min_t(int, max_write - con->out_msg_pos.page_pos,
total_max_write);
@ -891,7 +880,9 @@ static int write_partial_msg_pages(struct ceph_connection *con)
void *base;
u32 crc;
u32 tmpcrc = le32_to_cpu(con->out_msg->footer.data_crc);
char *kaddr;
kaddr = kmap(page);
BUG_ON(kaddr == NULL);
base = kaddr + con->out_msg_pos.page_pos + bio_offset;
crc = crc32c(tmpcrc, base, len);