From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tom Talpey Subject: Re: [Patch v2 06/15] CIFS: Introduce helper function to get page offset and length in smb_rqst Date: Tue, 26 Jun 2018 09:16:54 -0400 Message-ID: <33a2f951-10fd-fa94-4fb1-cade7f72cd77@talpey.com> References: <20180530194807.31657-1-longli@linuxonhyperv.com> <20180530194807.31657-7-longli@linuxonhyperv.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Long Li , Steve French , "linux-cifs@vger.kernel.org" , "samba-technical@lists.samba.org" , "linux-kernel@vger.kernel.org" , "linux-rdma@vger.kernel.org" List-Id: linux-rdma@vger.kernel.org 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 >>> >>> 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 >>> --- >>> 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.