Re: [Patch v2 06/15] CIFS: Introduce helper function to get page offset and length in smb_rqst

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On 6/25/2018 5:14 PM, Long Li wrote:
Subject: Re: [Patch v2 06/15] CIFS: Introduce helper function to get page
offset and length in smb_rqst

On 5/30/2018 3:47 PM, Long Li wrote:
From: Long Li <longli@xxxxxxxxxxxxx>

Introduce a function rqst_page_get_length to return the page offset
and length for a given page in smb_rqst. This function is to be used
by following patches.

Signed-off-by: Long Li <longli@xxxxxxxxxxxxx>
---
   fs/cifs/cifsproto.h |  3 +++
   fs/cifs/misc.c      | 17 +++++++++++++++++
   2 files changed, 20 insertions(+)

diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h index
7933c5f..89dda14 100644
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -557,4 +557,7 @@ int cifs_alloc_hash(const char *name, struct
crypto_shash **shash,
   		    struct sdesc **sdesc);
   void cifs_free_hash(struct crypto_shash **shash, struct sdesc
**sdesc);

+extern void rqst_page_get_length(struct smb_rqst *rqst, unsigned int
page,
+				unsigned int *len, unsigned int *offset);
+
   #endif			/* _CIFSPROTO_H */
diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c index 96849b5..e951417
100644
--- a/fs/cifs/misc.c
+++ b/fs/cifs/misc.c
@@ -905,3 +905,20 @@ cifs_free_hash(struct crypto_shash **shash,
struct sdesc **sdesc)
   		crypto_free_shash(*shash);
   	*shash = NULL;
   }
+
+/**
+ * rqst_page_get_length - obtain the length and offset for a page in
+smb_rqst
+ * Input: rqst - a smb_rqst, page - a page index for rqst
+ * Output: *len - the length for this page, *offset - the offset for
+this page  */ void rqst_page_get_length(struct smb_rqst *rqst,
+unsigned int page,
+				unsigned int *len, unsigned int *offset) {
+	*len = rqst->rq_pagesz;
+	*offset = (page == 0) ? rqst->rq_offset : 0;

Really? Page 0 always has a zero offset??

I think you are misreading this line. The offset for page 0 is rq_offset, the offset for all subsequent pages are 0.

Ah, yes, sorry I did read it incorrectly.
+
+	if (rqst->rq_npages == 1 || page == rqst->rq_npages-1)
+		*len = rqst->rq_tailsz;
+	else if (page == 0)
+		*len = rqst->rq_pagesz - rqst->rq_offset; }


This subroutine does what patch 5 does inline. Why not push this patch up in
the sequence and use the helper?

This is actually a little different. This function returns the length and offset for a given page in the request. There might be multiple pages in a request.

Ok, but I still think there is quite a bit of inline computation of
this stuff that would more clearly and more robustly be done in a set
of common functions. If someone ever touches the code to support a
new upper layer, or even integrate with more complex compounding,
things will get ugly fast.

The other function calculates the total length of all the pages in a request.

Again, a great candidate for a common set of subroutines, IMO.

Tom.
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