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Message-Id: <1417724597-17099-2-git-send-email-viro@ZenIV.linux.org.uk>
Date: Thu, 4 Dec 2014 20:23:06 +0000
From: Al Viro <viro@...IV.linux.org.uk>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
netdev@...r.kernel.org
Subject: [RFC][PATCH 02/13] iov_iter.c: iterate_and_advance
From: Al Viro <viro@...iv.linux.org.uk>
same as iterate_all_kinds, but iterator is moved to the position past
the last byte we'd handled.
iov_iter_advance() converted to it
Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
mm/iov_iter.c | 104 ++++++++++++++++------------------------------------------
1 file changed, 28 insertions(+), 76 deletions(-)
diff --git a/mm/iov_iter.c b/mm/iov_iter.c
index 798fcb4..e91bf0a 100644
--- a/mm/iov_iter.c
+++ b/mm/iov_iter.c
@@ -70,6 +70,33 @@
} \
}
+#define iterate_and_advance(i, n, v, I, B) { \
+ size_t skip = i->iov_offset; \
+ if (unlikely(i->type & ITER_BVEC)) { \
+ const struct bio_vec *bvec; \
+ struct bio_vec v; \
+ iterate_bvec(i, n, v, bvec, skip, (B)) \
+ if (skip == bvec->bv_len) { \
+ bvec++; \
+ skip = 0; \
+ } \
+ i->nr_segs -= bvec - i->bvec; \
+ i->bvec = bvec; \
+ } else { \
+ const struct iovec *iov; \
+ struct iovec v; \
+ iterate_iovec(i, n, v, iov, skip, (I)) \
+ if (skip == iov->iov_len) { \
+ iov++; \
+ skip = 0; \
+ } \
+ i->nr_segs -= iov - i->iov; \
+ i->iov = iov; \
+ } \
+ i->count -= n; \
+ i->iov_offset = skip; \
+}
+
static size_t copy_to_iter_iovec(void *from, size_t bytes, struct iov_iter *i)
{
size_t skip, copy, left, wanted;
@@ -366,42 +393,6 @@ static size_t zero_iovec(size_t bytes, struct iov_iter *i)
return wanted - bytes;
}
-static void advance_iovec(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 iovec *iov = i->iov;
- 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 && !iov->iov_len)) {
- int copy;
-
- copy = min(bytes, iov->iov_len - base);
- BUG_ON(!i->count || i->count < copy);
- i->count -= copy;
- bytes -= copy;
- base += copy;
- if (iov->iov_len == base) {
- iov++;
- nr_segs--;
- base = 0;
- }
- }
- i->iov = iov;
- i->iov_offset = base;
- i->nr_segs = nr_segs;
- }
-}
-
/*
* Fault in the first iovec of the given iov_iter, to a maximum length
* of bytes. Returns 0 on success, or non-zero if the memory could not be
@@ -685,42 +676,6 @@ static size_t zero_bvec(size_t bytes, struct iov_iter *i)
return wanted - 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 ssize_t get_pages_bvec(struct iov_iter *i,
struct page **pages, size_t maxsize, unsigned maxpages,
size_t *start)
@@ -849,10 +804,7 @@ 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);
+ iterate_and_advance(i, size, v, 0, 0)
}
EXPORT_SYMBOL(iov_iter_advance);
--
2.1.3
--
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