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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