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md/async: don't pass a memory pointer as a page pointer.

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md/raid6 passes a list of 'struct page *' to the async_tx routines,
which then either DMA map them for offload, or take the page_address
for CPU based calculations.

For RAID6 we sometime leave 'blanks' in the list of pages.
For CPU based calcs, we want to treat theses as a page of zeros.
For offloaded calculations, we simply don't pass a page to the
hardware.

Currently the 'blanks' are encoded as a pointer to
raid6_empty_zero_page.  This is a 4096 byte memory region, not a
'struct page'.  This is mostly handled correctly but is rather ugly.

So change the code to pass and expect a NULL pointer for the blanks.
When taking page_address of a page, we need to check for a NULL and
in that case use raid6_empty_zero_page.

Signed-off-by: NeilBrown <neilb@suse.de>
This commit is contained in:
NeilBrown
2009-10-16 16:40:25 +11:00
parent 5e5e3e78ed
commit 5dd33c9a4c
3 changed files with 17 additions and 18 deletions
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16
crypto/async_tx/async_raid6_recov.c
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@@ -263,10 +263,10 @@ __2data_recov_n(int disks, size_t bytes, int faila, int failb,
* delta p and delta q
*/
dp = blocks[faila];
blocks[faila] = (void *)raid6_empty_zero_page;
blocks[faila] = NULL;
blocks[disks-2] = dp;
dq = blocks[failb];
blocks[failb] = (void *)raid6_empty_zero_page;
blocks[failb] = NULL;
blocks[disks-1] = dq;
init_async_submit(submit, ASYNC_TX_FENCE, tx, NULL, NULL, scribble);
@@ -338,7 +338,10 @@ async_raid6_2data_recov(int disks, size_t bytes, int faila, int failb,
async_tx_quiesce(&submit->depend_tx);
for (i = 0; i < disks; i++)
ptrs[i] = page_address(blocks[i]);
if (blocks[i] == NULL)
ptrs[i] = (void*)raid6_empty_zero_page;
else
ptrs[i] = page_address(blocks[i]);
raid6_2data_recov(disks, bytes, faila, failb, ptrs);
@@ -398,7 +401,10 @@ async_raid6_datap_recov(int disks, size_t bytes, int faila,
async_tx_quiesce(&submit->depend_tx);
for (i = 0; i < disks; i++)
ptrs[i] = page_address(blocks[i]);
if (blocks[i] == NULL)
ptrs[i] = (void*)raid6_empty_zero_page;
else
ptrs[i] = page_address(blocks[i]);
raid6_datap_recov(disks, bytes, faila, ptrs);
@@ -414,7 +420,7 @@ async_raid6_datap_recov(int disks, size_t bytes, int faila,
* Use the dead data page as temporary storage for delta q
*/
dq = blocks[faila];
blocks[faila] = (void *)raid6_empty_zero_page;
blocks[faila] = NULL;
blocks[disks-1] = dq;
/* in the 4 disk case we only need to perform a single source