[Ocfs2-tools-devel] [PATCH 3/3] tunefs.ocfs2: Use one I/O cache.

[Joel Becker]

We nest ocfs2_filesys structures for each operation.  However, this can
mean that the I/O cache on the master filesys is stale when a child
filesys has written to its own cache.

Instead, we'll create an I/O cache on the master filesys and share it in
the children.  That way all operations have a consistent view of the
disk.

Signed-off-by: Joel Becker <joel.becker at oracle.com>
---
 tunefs.ocfs2/libocfs2ne.c |   28 ++++++++++++++++++++++++++++
 1 files changed, 28 insertions(+), 0 deletions(-)

diff --git a/tunefs.ocfs2/libocfs2ne.c b/tunefs.ocfs2/libocfs2ne.c
index f588596..5044f65 100644
--- a/tunefs.ocfs2/libocfs2ne.c
+++ b/tunefs.ocfs2/libocfs2ne.c
@@ -1259,10 +1259,21 @@ static void tunefs_init_cache(ocfs2_filesys *fs)
 {
 	errcode_t err;
 	struct tunefs_private *tp = to_private(fs);
+	struct tunefs_filesystem_state *state = tunefs_get_state(fs);
 	uint64_t blocks_wanted;
 	int scale_down;
 
 	/*
+	 * We have one I/O cache for all ocfs2_filesys structures.  This
+	 * guarantees a consistent view of the disk.  The master filesys
+	 * allocates it, child filesyses just use it.
+	 */
+	if (state->ts_master != fs) {
+		fs->fs_io = state->ts_master->fs_io;
+		return;
+	}
+
+	/*
 	 * Operations needing a large cache really want enough to
 	 * hold the whole filesystem in memory.  The rest of the
 	 * operations don't need much at all.  A cache big enough to
@@ -1314,6 +1325,21 @@ static void tunefs_init_cache(ocfs2_filesys *fs)
 	}
 }
 
+static void tunefs_drop_cache(ocfs2_filesys *fs)
+{
+	struct tunefs_filesystem_state *state = tunefs_get_state(fs);
+
+	/*
+	 * The master filesys created our cache.  We don't want
+	 * ocfs2_close() to kill it if we're closing a non-master,
+	 * so kill the pointer for those.
+	 */
+	if (state->ts_master == fs)
+		io_destroy_cache(fs->fs_io);
+	else
+		fs->fs_io = NULL;
+}
+
 static errcode_t tunefs_add_fs(ocfs2_filesys *fs, int flags)
 {
 	errcode_t err;
@@ -1470,6 +1496,7 @@ errcode_t tunefs_open(const char *device, int flags,
 out:
 	if (err && !tunefs_special_errorp(err)) {
 		if (fs) {
+			tunefs_drop_cache(fs);
 			tunefs_remove_fs(fs);
 			ocfs2_close(fs);
 			fs = NULL;
@@ -1499,6 +1526,7 @@ errcode_t tunefs_close(ocfs2_filesys *fs)
 		if (!err)
 			err = tmp;
 
+		tunefs_drop_cache(fs);
 		tunefs_remove_fs(fs);
 		tmp = ocfs2_close(fs);
 		if (!err)
-- 
1.6.3.1