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SubjectRe: [Patch v2 03/15] CIFS: Use offset when reading pages
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On 5/30/2018 3:47 PM, Long Li wrote:
> From: Long Li <longli@microsoft.com>
>
> With offset defined in rdata, transport functions need to look at this
> offset when reading data into the correct places in pages.
>
> Signed-off-by: Long Li <longli@microsoft.com>
> ---
> fs/cifs/cifsproto.h | 4 +++-
> fs/cifs/connect.c | 5 +++--
> fs/cifs/file.c | 52 +++++++++++++++++++++++++++++++++++++---------------
> fs/cifs/smb2ops.c | 2 +-
> fs/cifs/smb2pdu.c | 1 +
> 5 files changed, 45 insertions(+), 19 deletions(-)
>
> diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
> index dc80f84..1f27d8e 100644
> --- a/fs/cifs/cifsproto.h
> +++ b/fs/cifs/cifsproto.h
> @@ -203,7 +203,9 @@ extern void dequeue_mid(struct mid_q_entry *mid, bool malformed);
> extern int cifs_read_from_socket(struct TCP_Server_Info *server, char *buf,
> unsigned int to_read);
> extern int cifs_read_page_from_socket(struct TCP_Server_Info *server,
> - struct page *page, unsigned int to_read);
> + struct page *page,
> + unsigned int page_offset,
> + unsigned int to_read);
> extern int cifs_setup_cifs_sb(struct smb_vol *pvolume_info,
> struct cifs_sb_info *cifs_sb);
> extern int cifs_match_super(struct super_block *, void *);
> diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
> index 83b0234..8501da0 100644
> --- a/fs/cifs/connect.c
> +++ b/fs/cifs/connect.c
> @@ -594,10 +594,11 @@ cifs_read_from_socket(struct TCP_Server_Info *server, char *buf,
>
> int
> cifs_read_page_from_socket(struct TCP_Server_Info *server, struct page *page,
> - unsigned int to_read)
> + unsigned int page_offset, unsigned int to_read)
> {
> struct msghdr smb_msg;
> - struct bio_vec bv = {.bv_page = page, .bv_len = to_read};
> + struct bio_vec bv = {
> + .bv_page = page, .bv_len = to_read, .bv_offset = page_offset};
> iov_iter_bvec(&smb_msg.msg_iter, READ | ITER_BVEC, &bv, 1, to_read);
> return cifs_readv_from_socket(server, &smb_msg);
> }
> diff --git a/fs/cifs/file.c b/fs/cifs/file.c
> index 1c98293..87eece6 100644
> --- a/fs/cifs/file.c
> +++ b/fs/cifs/file.c
> @@ -3026,12 +3026,20 @@ uncached_fill_pages(struct TCP_Server_Info *server,
> int result = 0;
> unsigned int i;
> unsigned int nr_pages = rdata->nr_pages;
> + unsigned int page_offset = rdata->page_offset;
>
> rdata->got_bytes = 0;
> rdata->tailsz = PAGE_SIZE;
> for (i = 0; i < nr_pages; i++) {
> struct page *page = rdata->pages[i];
> size_t n;
> + unsigned int segment_size = rdata->pagesz;
> +
> + if (i == 0)
> + segment_size -= page_offset;
> + else
> + page_offset = 0;
> +
>
> if (len <= 0) {
> /* no need to hold page hostage */
> @@ -3040,24 +3048,25 @@ uncached_fill_pages(struct TCP_Server_Info *server,
> put_page(page);
> continue;
> }
> +
> n = len;
> - if (len >= PAGE_SIZE) {
> + if (len >= segment_size)
> /* enough data to fill the page */
> - n = PAGE_SIZE;
> - len -= n;
> - } else {
> - zero_user(page, len, PAGE_SIZE - len);
> + n = segment_size;
> + else
> rdata->tailsz = len;
> - len = 0;
> - }
> + len -= n;
> +
> if (iter)
> - result = copy_page_from_iter(page, 0, n, iter);
> + result = copy_page_from_iter(
> + page, page_offset, n, iter);
> #ifdef CONFIG_CIFS_SMB_DIRECT
> else if (rdata->mr)
> result = n;
> #endif

I hadn't noticed this type of xonditional code before. It's kind of ugly
to modify the data handling code like this. Do you plan to break this
out into an smbdirect-specific hander, like the cases above and below?

> else
> - result = cifs_read_page_from_socket(server, page, n);
> + result = cifs_read_page_from_socket(
> + server, page, page_offset, n);
> if (result < 0)
> break;
>
> @@ -3130,6 +3139,7 @@ cifs_send_async_read(loff_t offset, size_t len, struct cifsFileInfo *open_file,
> rdata->bytes = cur_len;
> rdata->pid = pid;
> rdata->pagesz = PAGE_SIZE;
> + rdata->tailsz = PAGE_SIZE;
> rdata->read_into_pages = cifs_uncached_read_into_pages;
> rdata->copy_into_pages = cifs_uncached_copy_into_pages;
> rdata->credits = credits;
> @@ -3574,6 +3584,7 @@ readpages_fill_pages(struct TCP_Server_Info *server,
> u64 eof;
> pgoff_t eof_index;
> unsigned int nr_pages = rdata->nr_pages;
> + unsigned int page_offset = rdata->page_offset;
>
> /* determine the eof that the server (probably) has */
> eof = CIFS_I(rdata->mapping->host)->server_eof;
> @@ -3584,13 +3595,21 @@ readpages_fill_pages(struct TCP_Server_Info *server,
> rdata->tailsz = PAGE_SIZE;
> for (i = 0; i < nr_pages; i++) {
> struct page *page = rdata->pages[i];
> - size_t n = PAGE_SIZE;
> + unsigned int to_read = rdata->pagesz;
> + size_t n;
> +
> + if (i == 0)
> + to_read -= page_offset;
> + else
> + page_offset = 0;
> +
> + n = to_read;
>
> - if (len >= PAGE_SIZE) {
> - len -= PAGE_SIZE;
> + if (len >= to_read) {
> + len -= to_read;
> } else if (len > 0) {
> /* enough for partial page, fill and zero the rest */
> - zero_user(page, len, PAGE_SIZE - len);
> + zero_user(page, len + page_offset, to_read - len);
> n = rdata->tailsz = len;
> len = 0;
> } else if (page->index > eof_index) {
> @@ -3622,13 +3641,15 @@ readpages_fill_pages(struct TCP_Server_Info *server,
> }
>
> if (iter)
> - result = copy_page_from_iter(page, 0, n, iter);
> + result = copy_page_from_iter(
> + page, page_offset, n, iter);
> #ifdef CONFIG_CIFS_SMB_DIRECT
> else if (rdata->mr)
> result = n;
> #endif

Ditto previous comment/question.

> else
> - result = cifs_read_page_from_socket(server, page, n);
> + result = cifs_read_page_from_socket(
> + server, page, page_offset, n);
> if (result < 0)
> break;
>
> @@ -3807,6 +3828,7 @@ static int cifs_readpages(struct file *file, struct address_space *mapping,
> rdata->bytes = bytes;
> rdata->pid = pid;
> rdata->pagesz = PAGE_SIZE;
> + rdata->tailsz = PAGE_SIZE;
> rdata->read_into_pages = cifs_readpages_read_into_pages;
> rdata->copy_into_pages = cifs_readpages_copy_into_pages;
> rdata->credits = credits;
> diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
> index 7c0edd2..1fa1c29 100644
> --- a/fs/cifs/smb2ops.c
> +++ b/fs/cifs/smb2ops.c
> @@ -2467,7 +2467,7 @@ read_data_into_pages(struct TCP_Server_Info *server, struct page **pages,
> zero_user(page, len, PAGE_SIZE - len);
> len = 0;
> }
> - length = cifs_read_page_from_socket(server, page, n);
> + length = cifs_read_page_from_socket(server, page, 0, n);
> if (length < 0)
> return length;
> server->total_read += length;
> diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
> index a02f6b6..f603fbe 100644
> --- a/fs/cifs/smb2pdu.c
> +++ b/fs/cifs/smb2pdu.c
> @@ -2683,6 +2683,7 @@ smb2_readv_callback(struct mid_q_entry *mid)
> struct smb_rqst rqst = { .rq_iov = rdata->iov,
> .rq_nvec = 2,
> .rq_pages = rdata->pages,
> + .rq_offset = rdata->page_offset,
> .rq_npages = rdata->nr_pages,
> .rq_pagesz = rdata->pagesz,
> .rq_tailsz = rdata->tailsz };
>

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