| Re: [PATCH 1/4] fuse: add basic support of iovec[] to fuse_req [message #47382 is a reply to message #47196] |
Wed, 08 August 2012 16:02   |
Miklos Szeredi
Messages: 161
Registered: April 2007
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Senior Member |
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Maxim Patlasov <mpatlasov@parallels.com> writes:
> The patch allows fuse_req to refer to array of iovec-s describing
> layout of user-data over req->pages. fuse_copy_pages() is re-worked to
> support both cased: former layout where pages[] corresponded to <buf, len>
> and newer one where pages[] corresponds to iovec[].
>
> Signed-off-by: Maxim Patlasov <mpatlasov@parallels.com>
> ---
> fs/fuse/dev.c | 52 +++++++++++++++++++++++++++++++++++++++++++++++++---
> fs/fuse/fuse_i.h | 12 ++++++++++--
> 2 files changed, 59 insertions(+), 5 deletions(-)
>
> diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
> index 7df2b5e..cdae525 100644
> --- a/fs/fuse/dev.c
> +++ b/fs/fuse/dev.c
> @@ -850,9 +850,9 @@ static int fuse_copy_page(struct fuse_copy_state *cs, struct page **pagep,
> return 0;
> }
>
> -/* Copy pages in the request to/from userspace buffer */
> -static int fuse_copy_pages(struct fuse_copy_state *cs, unsigned nbytes,
> - int zeroing)
> +/* Start from addr(pages[0]) + page_offset. No holes in the middle. */
> +static int fuse_copy_pages_for_buf(struct fuse_copy_state *cs, unsigned nbytes,
> + int zeroing)
> {
> unsigned i;
> struct fuse_req *req = cs->req;
> @@ -874,6 +874,52 @@ static int fuse_copy_pages(struct fuse_copy_state *cs, unsigned nbytes,
> return 0;
> }
>
> +/* Take iov_offset as offset in iovec[0]. Iterate based on iovec[].iov_len */
> +static int fuse_copy_pages_for_iovec(struct fuse_copy_state *cs,
> + unsigned nbytes, int zeroing)
> +{
> + unsigned i;
> + struct fuse_req *req = cs->req;
> + const struct iovec *iov = req->iovec;
> + unsigned iov_offset = req->iov_offset;
> +
> + for (i = 0; i < req->num_pages && (nbytes || zeroing); i++) {
> + int err;
> + unsigned long user_addr = (unsigned long)iov->iov_base +
> + iov_offset;
> + unsigned offset = user_addr & ~PAGE_MASK;
> + unsigned count = min_t(size_t, PAGE_SIZE - offset,
> + iov->iov_len - iov_offset);
It would be much cleaner if we didn't have to deal with the original
iovec here, but only offset and length relative to the page.
I understand that that would mean allocating an array for these. In the
other thread I mentioned the possibility of allocating the page array.
Instead of a page array, we could have an array of (pageptr, offset,
len) which would simplify the whole thing.
Thanks,
Miklos
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