When we want to add some prefix to the bio data, such as journal header,
we don't want to copy it from bio into a new larger memory. Instead, we need
a prefix page and suffix page to store the header and footer in bio_iter.
Signed-off-by: Dongsheng Yang <dongsheng.yang@xxxxxxxxxxxx>
---
include/linux/ceph/messenger.h | 9 ++++
net/ceph/messenger.c | 96 ++++++++++++++++++++++++++++++++----------
2 files changed, 83 insertions(+), 22 deletions(-)
diff --git a/include/linux/ceph/messenger.h b/include/linux/ceph/messenger.h
index 800a212..0da6a4b 100644
--- a/include/linux/ceph/messenger.h
+++ b/include/linux/ceph/messenger.h
@@ -87,6 +87,15 @@ enum ceph_msg_data_type {
struct ceph_bio_iter {
struct bio *bio;
struct bvec_iter iter;
+ size_t bio_len;
+
+ struct page *prefix_page;
+ unsigned int prefix_offset;
+ unsigned int prefix_len;
+
+ struct page *suffix_page;
+ unsigned int suffix_offset;
+ unsigned int suffix_len;
};
#define __ceph_bio_iter_advance_step(it, n, STEP) do { \
diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index 57fcc6b..64c70c5 100644
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -828,23 +828,46 @@ static void ceph_msg_data_bio_cursor_init(struct ceph_msg_data_cursor *cursor,
cursor->resid = min_t(size_t, length, data->bio_length);
*it = data->bio_pos;
- if (cursor->resid < it->iter.bi_size)
- it->iter.bi_size = cursor->resid;
- BUG_ON(cursor->resid < bio_iter_len(it->bio, it->iter));
- cursor->last_piece = cursor->resid == bio_iter_len(it->bio, it->iter);
+ if (cursor->resid < it->iter.bi_size + it->prefix_len + it->suffix_len)
+ it->iter.bi_size = cursor->resid - it->prefix_len - it->suffix_len;
+
+ it->bio_len = cursor->resid - it->prefix_len - it->suffix_len;
+ if (it->suffix_len) {
+ cursor->last_piece = cursor->resid == it->suffix_len;
+ } else if (it->bio_len) {
+ cursor->last_piece = cursor->resid == bio_iter_len(it->bio, it->iter);
+ } else if (it->prefix_len) {
+ cursor->last_piece = cursor->resid == it->prefix_len;
+ } else {
+ BUG();
+ }
}
static struct page *ceph_msg_data_bio_next(struct ceph_msg_data_cursor *cursor,
size_t *page_offset,
size_t *length)
{
- struct bio_vec bv = bio_iter_iovec(cursor->bio_iter.bio,
- cursor->bio_iter.iter);
+ struct ceph_bio_iter *it = &cursor->bio_iter;
- *page_offset = bv.bv_offset;
- *length = bv.bv_len;
- return bv.bv_page;
+ if (it->prefix_len) {
+ *page_offset = it->prefix_offset;
+ *length = it->prefix_len;
+ return it->prefix_page;
+ } else if (it->bio_len) {
+ struct bio_vec bv = bio_iter_iovec(cursor->bio_iter.bio,
+ cursor->bio_iter.iter);
+
+ *page_offset = bv.bv_offset;
+ *length = bv.bv_len;
+ return bv.bv_page;
+ } else {
+ BUG_ON(!it->suffix_len);
+
+ *page_offset = it->suffix_offset;
+ *length = it->suffix_len;
+ return it->suffix_page;
+ }
}
static bool ceph_msg_data_bio_advance(struct ceph_msg_data_cursor *cursor,
@@ -852,29 +875,58 @@ static bool ceph_msg_data_bio_advance(struct ceph_msg_data_cursor *cursor,
{
struct ceph_bio_iter *it = &cursor->bio_iter;
+ if (!bytes)
+ return false;
+
BUG_ON(bytes > cursor->resid);
- BUG_ON(bytes > bio_iter_len(it->bio, it->iter));
cursor->resid -= bytes;
- bio_advance_iter(it->bio, &it->iter, bytes);
+ if (it->prefix_len) {
+ BUG_ON(bytes > it->prefix_len);
+ it->prefix_offset += bytes;
+ it->prefix_len -= bytes;
+ if (it->prefix_len)
+ return false;
+ } else if (it->bio_len) {
+ BUG_ON(bytes > bio_iter_len(it->bio, it->iter));
+ bio_advance_iter(it->bio, &it->iter, bytes);
+ it->bio_len -= bytes;
+ if (!cursor->resid) {
+ BUG_ON(!cursor->last_piece);
+ return false; /* no more data */
+ }
+ if (it->iter.bi_size && it->iter.bi_bvec_done)
+ return false; /* more bytes to process in this segment */
+
+ if (it->bio_len && !it->iter.bi_size) {
+ it->bio = it->bio->bi_next;
+ it->iter = it->bio->bi_iter;
+ if (cursor->resid < it->iter.bi_size)
+ it->iter.bi_size = cursor->resid;
+ }
+ } else {
+ BUG_ON(!it->suffix_len);
+ it->suffix_offset += bytes;
+ it->suffix_len -= bytes;
+ if (it->suffix_len)
+ return false;
+ }
if (!cursor->resid) {
BUG_ON(!cursor->last_piece);
return false; /* no more data */
}
- if (!bytes || (it->iter.bi_size && it->iter.bi_bvec_done))
- return false; /* more bytes to process in this segment */
-
- if (!it->iter.bi_size) {
- it->bio = it->bio->bi_next;
- it->iter = it->bio->bi_iter;
- if (cursor->resid < it->iter.bi_size)
- it->iter.bi_size = cursor->resid;
+ BUG_ON(cursor->last_piece);
+ if (it->suffix_len) {
+ cursor->last_piece = cursor->resid == it->suffix_len;
+ } else if (it->bio_len) {
+ cursor->last_piece = cursor->resid == bio_iter_len(it->bio, it->iter);
+ } else if (it->prefix_len) {
+ cursor->last_piece = cursor->resid == it->prefix_len;
+ } else {
+ BUG();
}
- BUG_ON(cursor->last_piece);
- BUG_ON(cursor->resid < bio_iter_len(it->bio, it->iter));
- cursor->last_piece = cursor->resid == bio_iter_len(it->bio, it->iter);
return true;
}
#endif /* CONFIG_BLOCK */
--
1.8.3.1
