Re: [Patch v2 11/15] CIFS: Pass page offset for calculating signature

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On 5/30/2018 3:48 PM, Long Li wrote:
From: Long Li <longli@xxxxxxxxxxxxx>

When calculating signature for the packet, it needs to read into the
correct page offset for the data.

Signed-off-by: Long Li <longli@xxxxxxxxxxxxx>
---
  fs/cifs/cifsencrypt.c | 9 +++++----
  1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/fs/cifs/cifsencrypt.c b/fs/cifs/cifsencrypt.c
index a6ef088..e88303c 100644
--- a/fs/cifs/cifsencrypt.c
+++ b/fs/cifs/cifsencrypt.c
@@ -68,11 +68,12 @@ int __cifs_calc_signature(struct smb_rqst *rqst,
/* now hash over the rq_pages array */
  	for (i = 0; i < rqst->rq_npages; i++) {
-		void *kaddr = kmap(rqst->rq_pages[i]);
-		size_t len = rqst->rq_pagesz;
+		void *kaddr;
+		unsigned int len, offset;
- if (i == rqst->rq_npages - 1)
-			len = rqst->rq_tailsz;
+		rqst_page_get_length(rqst, i, &len, &offset);
+
+		kaddr = (char *) kmap(rqst->rq_pages[i]) + offset;

I suppose it's more robust to map a page at a time, but it's pretty
expensive. Is this the only way to iterate over a potentially very
large block of data? For example, a 1MB segment means 256 kmap/kunmaps.

Tom.

crypto_shash_update(shash, kaddr, len);
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