Re: [Patch v2 05/15] CIFS: Calculate the correct request length based on page offset and tail size
From: Tom Talpey <tom@talpey.com>
Date: 2018-06-24 02:07:14
Also in:
linux-cifs, lkml
On 5/30/2018 3:47 PM, Long Li wrote:
quoted hunk ↗ jump to hunk
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; + }
Wouldn't it be simpler to keep the original code, but then just subtract the rq_offset? buflen += rqst->rq_pagesz * (rqst->rq_npages - 1); buflen += rqst->rq_tailsz; buflen -= rqst->rq_offset; It's kind of confusing as written. Also, what if it's just one page, but has a non-zero offset? Is that somehow not possible? My suggested code would take that into account, yours doesn't. Tom.
} return buflen;