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Subject[Patch v3 05/16] CIFS: Calculate the correct request length based on page offset and tail size
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From: Long Li <longli@microsoft.com>

It's possible that the page offset is non-zero in the pages in a request,
change the function to calculate the correct data buffer length.

Signed-off-by: Long Li <longli@microsoft.com>
---
fs/cifs/transport.c | 20 +++++++++++++++++---
1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c
index 927226a..d6b5523 100644
--- a/fs/cifs/transport.c
+++ b/fs/cifs/transport.c
@@ -212,10 +212,24 @@ rqst_len(struct smb_rqst *rqst)
for (i = 0; i < rqst->rq_nvec; i++)
buflen += iov[i].iov_len;

- /* add in the page array if there is one */
+ /*
+ * Add in the page array if there is one. The caller needs to make
+ * sure rq_offset and rq_tailsz are set correctly. If a buffer of
+ * multiple pages ends at page boundary, rq_tailsz needs to be set to
+ * PAGE_SIZE.
+ */
if (rqst->rq_npages) {
- buflen += rqst->rq_pagesz * (rqst->rq_npages - 1);
- buflen += rqst->rq_tailsz;
+ if (rqst->rq_npages == 1)
+ buflen += rqst->rq_tailsz;
+ else {
+ /*
+ * If there is more than one page, calculate the
+ * buffer length based on rq_offset and rq_tailsz
+ */
+ buflen += rqst->rq_pagesz * (rqst->rq_npages - 1) -
+ rqst->rq_offset;
+ buflen += rqst->rq_tailsz;
+ }
}

return buflen;
--
2.7.4
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