[Ocfs2-tools-devel] [PATCH 01/11] Implement cache sharing for io channels

[Jan Kara]

Implement function io_share_cache() to allow sharing of caches for two
io channels.

Signed-off-by: Jan Kara <jack at suse.cz>
---
 include/ocfs2/ocfs2.h |    1 +
 libocfs2/unix_io.c    |   16 +++++++++++++++-
 2 files changed, 16 insertions(+), 1 deletions(-)

diff --git a/include/ocfs2/ocfs2.h b/include/ocfs2/ocfs2.h
index 8bf22c9..2b7dc54 100644
--- a/include/ocfs2/ocfs2.h
+++ b/include/ocfs2/ocfs2.h
@@ -248,6 +248,7 @@ errcode_t io_write_block_nocache(io_channel *channel, int64_t blkno, int count,
 errcode_t io_init_cache(io_channel *channel, size_t nr_blocks);
 void io_set_nocache(io_channel *channel, bool nocache);
 errcode_t io_init_cache_size(io_channel *channel, size_t bytes);
+errcode_t io_share_cache(io_channel *from, io_channel *to);
 errcode_t io_mlock_cache(io_channel *channel);
 void io_destroy_cache(io_channel *channel);
 
diff --git a/libocfs2/unix_io.c b/libocfs2/unix_io.c
index ccdaf93..4d16b0c 100644
--- a/libocfs2/unix_io.c
+++ b/libocfs2/unix_io.c
@@ -84,6 +84,7 @@ struct io_cache {
 	char *ic_data_buffer;
 	unsigned long ic_data_buffer_len;
 	int ic_locked;
+	int ic_use_count;
 };
 
 struct _io_channel {
@@ -479,7 +480,8 @@ static void io_free_cache(struct io_cache *ic)
 void io_destroy_cache(io_channel *channel)
 {
 	if (channel->io_cache) {
-		io_free_cache(channel->io_cache);
+		if (!--channel->io_cache->ic_use_count)
+			io_free_cache(channel->io_cache);
 		channel->io_cache = NULL;
 	}
 }
@@ -562,6 +564,7 @@ errcode_t io_init_cache(io_channel *channel, size_t nr_blocks)
 		list_add_tail(&icb_list[i].icb_list, &ic->ic_lru);
 	}
 
+	ic->ic_use_count = 1;
 	channel->io_cache = ic;
 
 out:
@@ -581,6 +584,17 @@ errcode_t io_init_cache_size(io_channel *channel, size_t bytes)
 }
 
 
+errcode_t io_share_cache(io_channel *from, io_channel *to)
+{
+	if (!from->io_cache)
+		return OCFS2_ET_INTERNAL_FAILURE;
+	if (to->io_cache)
+		return OCFS2_ET_INTERNAL_FAILURE;
+	to->io_cache = from->io_cache;
+	from->io_cache->ic_use_count++;
+	return 0;
+}
+
 static errcode_t io_validate_o_direct(io_channel *channel)
 {
 	errcode_t ret = OCFS2_ET_UNEXPECTED_BLOCK_SIZE;
-- 
1.6.0.2