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fuse: optimize fuse_get_user_pages()

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Let fuse_get_user_pages() pack as many iov-s to a single fuse_req as
possible. This is very beneficial in case of iov[] consisting of many
iov-s of relatively small sizes (e.g. PAGE_SIZE).

Signed-off-by: Maxim Patlasov <mpatlasov@parallels.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
This commit is contained in:
Maxim Patlasov 2012-10-26 19:50:29 +04:00 committed by Miklos Szeredi
parent b98d023a24
commit 7c190c8b9c
1 changed files with 51 additions and 28 deletions
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79
fs/fuse/file.c
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@ -1047,29 +1047,37 @@ static void fuse_release_user_pages(struct fuse_req *req, int write)
}
}
static inline void fuse_page_descs_length_init(struct fuse_req *req)
static inline void fuse_page_descs_length_init(struct fuse_req *req,
unsigned index, unsigned nr_pages)
{
int i;
for (i = 0; i < req->num_pages; i++)
for (i = index; i < index + nr_pages; i++)
req->page_descs[i].length = PAGE_SIZE -
req->page_descs[i].offset;
}
static inline unsigned long fuse_get_user_addr(const struct iov_iter *ii)
{
return (unsigned long)ii->iov->iov_base + ii->iov_offset;
}
static inline size_t fuse_get_frag_size(const struct iov_iter *ii,
size_t max_size)
{
return min(iov_iter_single_seg_count(ii), max_size);
}
static int fuse_get_user_pages(struct fuse_req *req, struct iov_iter *ii,
size_t *nbytesp, int write)
{
size_t nbytes = *nbytesp;
size_t frag_size = min(iov_iter_single_seg_count(ii), nbytes);
unsigned long user_addr;
unsigned offset;
int npages;
user_addr = (unsigned long)ii->iov->iov_base + ii->iov_offset;
offset = user_addr & ~PAGE_MASK;
size_t nbytes = 0; /* # bytes already packed in req */
/* Special case for kernel I/O: can copy directly into the buffer */
if (segment_eq(get_fs(), KERNEL_DS)) {
unsigned long user_addr = fuse_get_user_addr(ii);
size_t frag_size = fuse_get_frag_size(ii, *nbytesp);
if (write)
req->in.args[1].value = (void *) user_addr;
else
@ -1080,30 +1088,45 @@ static int fuse_get_user_pages(struct fuse_req *req, struct iov_iter *ii,
return 0;
}
nbytes = min_t(size_t, frag_size, FUSE_MAX_PAGES_PER_REQ << PAGE_SHIFT);
npages = (nbytes + offset + PAGE_SIZE - 1) >> PAGE_SHIFT;
npages = clamp(npages, 1, FUSE_MAX_PAGES_PER_REQ);
npages = get_user_pages_fast(user_addr, npages, !write, req->pages);
if (npages < 0)
return npages;
while (nbytes < *nbytesp && req->num_pages < FUSE_MAX_PAGES_PER_REQ) {
unsigned npages;
unsigned long user_addr = fuse_get_user_addr(ii);
unsigned offset = user_addr & ~PAGE_MASK;
size_t frag_size = fuse_get_frag_size(ii, *nbytesp - nbytes);
int ret;
req->num_pages = npages;
req->page_descs[0].offset = offset;
fuse_page_descs_length_init(req);
unsigned n = FUSE_MAX_PAGES_PER_REQ - req->num_pages;
frag_size = min_t(size_t, frag_size, n << PAGE_SHIFT);
npages = (frag_size + offset + PAGE_SIZE - 1) >> PAGE_SHIFT;
npages = clamp(npages, 1U, n);
ret = get_user_pages_fast(user_addr, npages, !write,
&req->pages[req->num_pages]);
if (ret < 0)
return ret;
npages = ret;
frag_size = min_t(size_t, frag_size,
(npages << PAGE_SHIFT) - offset);
iov_iter_advance(ii, frag_size);
req->page_descs[req->num_pages].offset = offset;
fuse_page_descs_length_init(req, req->num_pages, npages);
req->num_pages += npages;
req->page_descs[req->num_pages - 1].length -=
(npages << PAGE_SHIFT) - offset - frag_size;
nbytes += frag_size;
}
if (write)
req->in.argpages = 1;
else
req->out.argpages = 1;
nbytes = (req->num_pages << PAGE_SHIFT) - req->page_descs[0].offset;
if (frag_size < nbytes)
req->page_descs[req->num_pages - 1].length -=
nbytes - frag_size;
*nbytesp = min(frag_size, nbytes);
iov_iter_advance(ii, *nbytesp);
*nbytesp = nbytes;
return 0;
}
@ -1948,7 +1971,7 @@ long fuse_do_ioctl(struct file *file, unsigned int cmd, unsigned long arg,
}
memcpy(req->pages, pages, sizeof(req->pages[0]) * num_pages);
req->num_pages = num_pages;
fuse_page_descs_length_init(req);
fuse_page_descs_length_init(req, 0, req->num_pages);
/* okay, let's send it to the client */
req->in.h.opcode = FUSE_IOCTL;