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authorAl Viro <viro@zeniv.linux.org.uk>2014-04-04 23:12:29 -0400
committerAl Viro <viro@zeniv.linux.org.uk>2014-05-06 17:39:45 -0400
commit62a8067a7f35dba2de501c9cb00e4cf36da90bc0 (patch)
treebb008456891c13b9d8a25825a10074efb861cd88 /mm/iov_iter.c
parent81055e584f9d743cb13dc7944923d817c20f089d (diff)
downloadlinux-stericsson-62a8067a7f35dba2de501c9cb00e4cf36da90bc0.tar.gz
bio_vec-backed iov_iter
New variant of iov_iter - ITER_BVEC in iter->type, backed with bio_vec array instead of iovec one. Primitives taught to deal with such beasts, __swap_write() switched to using that kind of iov_iter. Note that bio_vec is just a <page, offset, length> triple - there's nothing block-specific about it. I've left the definition where it was, but took it from under ifdef CONFIG_BLOCK. Next target: ->splice_write()... Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'mm/iov_iter.c')
-rw-r--r--mm/iov_iter.c390
1 files changed, 358 insertions, 32 deletions
diff --git a/mm/iov_iter.c b/mm/iov_iter.c
index fcdaaab438b6..7b5dbd1517b5 100644
--- a/mm/iov_iter.c
+++ b/mm/iov_iter.c
@@ -4,7 +4,7 @@
#include <linux/slab.h>
#include <linux/vmalloc.h>
-size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
+static size_t copy_page_to_iter_iovec(struct page *page, size_t offset, size_t bytes,
struct iov_iter *i)
{
size_t skip, copy, left, wanted;
@@ -84,9 +84,8 @@ done:
i->iov_offset = skip;
return wanted - bytes;
}
-EXPORT_SYMBOL(copy_page_to_iter);
-size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
+static size_t copy_page_from_iter_iovec(struct page *page, size_t offset, size_t bytes,
struct iov_iter *i)
{
size_t skip, copy, left, wanted;
@@ -166,7 +165,6 @@ done:
i->iov_offset = skip;
return wanted - bytes;
}
-EXPORT_SYMBOL(copy_page_from_iter);
static size_t __iovec_copy_from_user_inatomic(char *vaddr,
const struct iovec *iov, size_t base, size_t bytes)
@@ -195,7 +193,7 @@ static size_t __iovec_copy_from_user_inatomic(char *vaddr,
* were successfully copied. If a fault is encountered then return the number of
* bytes which were copied.
*/
-size_t iov_iter_copy_from_user_atomic(struct page *page,
+static size_t copy_from_user_atomic_iovec(struct page *page,
struct iov_iter *i, unsigned long offset, size_t bytes)
{
char *kaddr;
@@ -215,9 +213,8 @@ size_t iov_iter_copy_from_user_atomic(struct page *page,
return copied;
}
-EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
-void iov_iter_advance(struct iov_iter *i, size_t bytes)
+static void advance_iovec(struct iov_iter *i, size_t bytes)
{
BUG_ON(i->count < bytes);
@@ -252,7 +249,6 @@ void iov_iter_advance(struct iov_iter *i, size_t bytes)
i->nr_segs = nr_segs;
}
}
-EXPORT_SYMBOL(iov_iter_advance);
/*
* Fault in the first iovec of the given iov_iter, to a maximum length
@@ -265,26 +261,16 @@ EXPORT_SYMBOL(iov_iter_advance);
*/
int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
{
- char __user *buf = i->iov->iov_base + i->iov_offset;
- bytes = min(bytes, i->iov->iov_len - i->iov_offset);
- return fault_in_pages_readable(buf, bytes);
+ if (!(i->type & ITER_BVEC)) {
+ char __user *buf = i->iov->iov_base + i->iov_offset;
+ bytes = min(bytes, i->iov->iov_len - i->iov_offset);
+ return fault_in_pages_readable(buf, bytes);
+ }
+ return 0;
}
EXPORT_SYMBOL(iov_iter_fault_in_readable);
-/*
- * Return the count of just the current iov_iter segment.
- */
-size_t iov_iter_single_seg_count(const struct iov_iter *i)
-{
- const struct iovec *iov = i->iov;
- if (i->nr_segs == 1)
- return i->count;
- else
- return min(i->count, iov->iov_len - i->iov_offset);
-}
-EXPORT_SYMBOL(iov_iter_single_seg_count);
-
-unsigned long iov_iter_alignment(const struct iov_iter *i)
+static unsigned long alignment_iovec(const struct iov_iter *i)
{
const struct iovec *iov = i->iov;
unsigned long res;
@@ -307,7 +293,6 @@ unsigned long iov_iter_alignment(const struct iov_iter *i)
res |= (unsigned long)iov->iov_base | size;
return res;
}
-EXPORT_SYMBOL(iov_iter_alignment);
void iov_iter_init(struct iov_iter *i, int direction,
const struct iovec *iov, unsigned long nr_segs,
@@ -315,7 +300,7 @@ void iov_iter_init(struct iov_iter *i, int direction,
{
/* It will get better. Eventually... */
if (segment_eq(get_fs(), KERNEL_DS))
- direction |= REQ_KERNEL;
+ direction |= ITER_KVEC;
i->type = direction;
i->iov = iov;
i->nr_segs = nr_segs;
@@ -324,7 +309,7 @@ void iov_iter_init(struct iov_iter *i, int direction,
}
EXPORT_SYMBOL(iov_iter_init);
-ssize_t iov_iter_get_pages(struct iov_iter *i,
+static ssize_t get_pages_iovec(struct iov_iter *i,
struct page **pages, size_t maxsize,
size_t *start)
{
@@ -349,9 +334,8 @@ ssize_t iov_iter_get_pages(struct iov_iter *i,
return res;
return (res == n ? len : res * PAGE_SIZE) - *start;
}
-EXPORT_SYMBOL(iov_iter_get_pages);
-ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
+static ssize_t get_pages_alloc_iovec(struct iov_iter *i,
struct page ***pages, size_t maxsize,
size_t *start)
{
@@ -387,9 +371,8 @@ ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
*pages = p;
return (res == n ? len : res * PAGE_SIZE) - *start;
}
-EXPORT_SYMBOL(iov_iter_get_pages_alloc);
-int iov_iter_npages(const struct iov_iter *i, int maxpages)
+static int iov_iter_npages_iovec(const struct iov_iter *i, int maxpages)
{
size_t offset = i->iov_offset;
size_t size = i->count;
@@ -414,4 +397,347 @@ int iov_iter_npages(const struct iov_iter *i, int maxpages)
}
return min(npages, maxpages);
}
+
+static void memcpy_from_page(char *to, struct page *page, size_t offset, size_t len)
+{
+ char *from = kmap_atomic(page);
+ memcpy(to, from + offset, len);
+ kunmap_atomic(from);
+}
+
+static void memcpy_to_page(struct page *page, size_t offset, char *from, size_t len)
+{
+ char *to = kmap_atomic(page);
+ memcpy(to + offset, from, len);
+ kunmap_atomic(to);
+}
+
+static size_t copy_page_to_iter_bvec(struct page *page, size_t offset, size_t bytes,
+ struct iov_iter *i)
+{
+ size_t skip, copy, wanted;
+ const struct bio_vec *bvec;
+ void *kaddr, *from;
+
+ if (unlikely(bytes > i->count))
+ bytes = i->count;
+
+ if (unlikely(!bytes))
+ return 0;
+
+ wanted = bytes;
+ bvec = i->bvec;
+ skip = i->iov_offset;
+ copy = min_t(size_t, bytes, bvec->bv_len - skip);
+
+ kaddr = kmap_atomic(page);
+ from = kaddr + offset;
+ memcpy_to_page(bvec->bv_page, skip + bvec->bv_offset, from, copy);
+ skip += copy;
+ from += copy;
+ bytes -= copy;
+ while (bytes) {
+ bvec++;
+ copy = min(bytes, (size_t)bvec->bv_len);
+ memcpy_to_page(bvec->bv_page, bvec->bv_offset, from, copy);
+ skip = copy;
+ from += copy;
+ bytes -= copy;
+ }
+ kunmap_atomic(kaddr);
+ if (skip == bvec->bv_len) {
+ bvec++;
+ skip = 0;
+ }
+ i->count -= wanted - bytes;
+ i->nr_segs -= bvec - i->bvec;
+ i->bvec = bvec;
+ i->iov_offset = skip;
+ return wanted - bytes;
+}
+
+static size_t copy_page_from_iter_bvec(struct page *page, size_t offset, size_t bytes,
+ struct iov_iter *i)
+{
+ size_t skip, copy, wanted;
+ const struct bio_vec *bvec;
+ void *kaddr, *to;
+
+ if (unlikely(bytes > i->count))
+ bytes = i->count;
+
+ if (unlikely(!bytes))
+ return 0;
+
+ wanted = bytes;
+ bvec = i->bvec;
+ skip = i->iov_offset;
+
+ kaddr = kmap_atomic(page);
+
+ to = kaddr + offset;
+
+ copy = min(bytes, bvec->bv_len - skip);
+
+ memcpy_from_page(to, bvec->bv_page, bvec->bv_offset + skip, copy);
+
+ to += copy;
+ skip += copy;
+ bytes -= copy;
+
+ while (bytes) {
+ bvec++;
+ copy = min(bytes, (size_t)bvec->bv_len);
+ memcpy_from_page(to, bvec->bv_page, bvec->bv_offset, copy);
+ skip = copy;
+ to += copy;
+ bytes -= copy;
+ }
+ kunmap_atomic(kaddr);
+ if (skip == bvec->bv_len) {
+ bvec++;
+ skip = 0;
+ }
+ i->count -= wanted;
+ i->nr_segs -= bvec - i->bvec;
+ i->bvec = bvec;
+ i->iov_offset = skip;
+ return wanted;
+}
+
+static size_t copy_from_user_bvec(struct page *page,
+ struct iov_iter *i, unsigned long offset, size_t bytes)
+{
+ char *kaddr;
+ size_t left;
+ const struct bio_vec *bvec;
+ size_t base = i->iov_offset;
+
+ kaddr = kmap_atomic(page);
+ for (left = bytes, bvec = i->bvec; left; bvec++, base = 0) {
+ size_t copy = min(left, bvec->bv_len - base);
+ if (!bvec->bv_len)
+ continue;
+ memcpy_from_page(kaddr + offset, bvec->bv_page,
+ bvec->bv_offset + base, copy);
+ offset += copy;
+ left -= copy;
+ }
+ kunmap_atomic(kaddr);
+ return bytes;
+}
+
+static void advance_bvec(struct iov_iter *i, size_t bytes)
+{
+ BUG_ON(i->count < bytes);
+
+ if (likely(i->nr_segs == 1)) {
+ i->iov_offset += bytes;
+ i->count -= bytes;
+ } else {
+ const struct bio_vec *bvec = i->bvec;
+ size_t base = i->iov_offset;
+ unsigned long nr_segs = i->nr_segs;
+
+ /*
+ * The !iov->iov_len check ensures we skip over unlikely
+ * zero-length segments (without overruning the iovec).
+ */
+ while (bytes || unlikely(i->count && !bvec->bv_len)) {
+ int copy;
+
+ copy = min(bytes, bvec->bv_len - base);
+ BUG_ON(!i->count || i->count < copy);
+ i->count -= copy;
+ bytes -= copy;
+ base += copy;
+ if (bvec->bv_len == base) {
+ bvec++;
+ nr_segs--;
+ base = 0;
+ }
+ }
+ i->bvec = bvec;
+ i->iov_offset = base;
+ i->nr_segs = nr_segs;
+ }
+}
+
+static unsigned long alignment_bvec(const struct iov_iter *i)
+{
+ const struct bio_vec *bvec = i->bvec;
+ unsigned long res;
+ size_t size = i->count;
+ size_t n;
+
+ if (!size)
+ return 0;
+
+ res = bvec->bv_offset + i->iov_offset;
+ n = bvec->bv_len - i->iov_offset;
+ if (n >= size)
+ return res | size;
+ size -= n;
+ res |= n;
+ while (size > (++bvec)->bv_len) {
+ res |= bvec->bv_offset | bvec->bv_len;
+ size -= bvec->bv_len;
+ }
+ res |= bvec->bv_offset | size;
+ return res;
+}
+
+static ssize_t get_pages_bvec(struct iov_iter *i,
+ struct page **pages, size_t maxsize,
+ size_t *start)
+{
+ const struct bio_vec *bvec = i->bvec;
+ size_t len = bvec->bv_len - i->iov_offset;
+ if (len > i->count)
+ len = i->count;
+ if (len > maxsize)
+ len = maxsize;
+ *start = bvec->bv_offset + i->iov_offset;
+
+ get_page(*pages = bvec->bv_page);
+
+ return len;
+}
+
+static ssize_t get_pages_alloc_bvec(struct iov_iter *i,
+ struct page ***pages, size_t maxsize,
+ size_t *start)
+{
+ const struct bio_vec *bvec = i->bvec;
+ size_t len = bvec->bv_len - i->iov_offset;
+ if (len > i->count)
+ len = i->count;
+ if (len > maxsize)
+ len = maxsize;
+ *start = bvec->bv_offset + i->iov_offset;
+
+ *pages = kmalloc(sizeof(struct page *), GFP_KERNEL);
+ if (!*pages)
+ return -ENOMEM;
+
+ get_page(**pages = bvec->bv_page);
+
+ return len;
+}
+
+static int iov_iter_npages_bvec(const struct iov_iter *i, int maxpages)
+{
+ size_t offset = i->iov_offset;
+ size_t size = i->count;
+ const struct bio_vec *bvec = i->bvec;
+ int npages = 0;
+ int n;
+
+ for (n = 0; size && n < i->nr_segs; n++, bvec++) {
+ size_t len = bvec->bv_len - offset;
+ offset = 0;
+ if (unlikely(!len)) /* empty segment */
+ continue;
+ if (len > size)
+ len = size;
+ npages++;
+ if (npages >= maxpages) /* don't bother going further */
+ return maxpages;
+ size -= len;
+ offset = 0;
+ }
+ return min(npages, maxpages);
+}
+
+size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
+ struct iov_iter *i)
+{
+ if (i->type & ITER_BVEC)
+ return copy_page_to_iter_bvec(page, offset, bytes, i);
+ else
+ return copy_page_to_iter_iovec(page, offset, bytes, i);
+}
+EXPORT_SYMBOL(copy_page_to_iter);
+
+size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
+ struct iov_iter *i)
+{
+ if (i->type & ITER_BVEC)
+ return copy_page_from_iter_bvec(page, offset, bytes, i);
+ else
+ return copy_page_from_iter_iovec(page, offset, bytes, i);
+}
+EXPORT_SYMBOL(copy_page_from_iter);
+
+size_t iov_iter_copy_from_user_atomic(struct page *page,
+ struct iov_iter *i, unsigned long offset, size_t bytes)
+{
+ if (i->type & ITER_BVEC)
+ return copy_from_user_bvec(page, i, offset, bytes);
+ else
+ return copy_from_user_atomic_iovec(page, i, offset, bytes);
+}
+EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
+
+void iov_iter_advance(struct iov_iter *i, size_t size)
+{
+ if (i->type & ITER_BVEC)
+ advance_bvec(i, size);
+ else
+ advance_iovec(i, size);
+}
+EXPORT_SYMBOL(iov_iter_advance);
+
+/*
+ * Return the count of just the current iov_iter segment.
+ */
+size_t iov_iter_single_seg_count(const struct iov_iter *i)
+{
+ if (i->nr_segs == 1)
+ return i->count;
+ else if (i->type & ITER_BVEC)
+ return min(i->count, i->iov->iov_len - i->iov_offset);
+ else
+ return min(i->count, i->bvec->bv_len - i->iov_offset);
+}
+EXPORT_SYMBOL(iov_iter_single_seg_count);
+
+unsigned long iov_iter_alignment(const struct iov_iter *i)
+{
+ if (i->type & ITER_BVEC)
+ return alignment_bvec(i);
+ else
+ return alignment_iovec(i);
+}
+EXPORT_SYMBOL(iov_iter_alignment);
+
+ssize_t iov_iter_get_pages(struct iov_iter *i,
+ struct page **pages, size_t maxsize,
+ size_t *start)
+{
+ if (i->type & ITER_BVEC)
+ return get_pages_bvec(i, pages, maxsize, start);
+ else
+ return get_pages_iovec(i, pages, maxsize, start);
+}
+EXPORT_SYMBOL(iov_iter_get_pages);
+
+ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
+ struct page ***pages, size_t maxsize,
+ size_t *start)
+{
+ if (i->type & ITER_BVEC)
+ return get_pages_alloc_bvec(i, pages, maxsize, start);
+ else
+ return get_pages_alloc_iovec(i, pages, maxsize, start);
+}
+EXPORT_SYMBOL(iov_iter_get_pages_alloc);
+
+int iov_iter_npages(const struct iov_iter *i, int maxpages)
+{
+ if (i->type & ITER_BVEC)
+ return iov_iter_npages_bvec(i, maxpages);
+ else
+ return iov_iter_npages_iovec(i, maxpages);
+}
EXPORT_SYMBOL(iov_iter_npages);