[PATCH v3 08/12] fs/ceph: remove i_truncate_mutex, use i_fragtree_mutex for both

`i_fragtree_mutex` is only used for directories and `i_truncate_mutex`
is only used for regular files.  Since these two fields will never be
both be used on any given object, let's merge them into one.

(This is a minimal diff that defines a preprocessor macro, to avoid
refactoring all code lines using these two mutexes.)

This reduces the size of `struct ceph_inode_info` by 8 bytes.

Signed-off-by: Max Kellermann <[email protected]>
---
 fs/ceph/inode.c | 1 -
 fs/ceph/super.h | 6 +++++-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
index e79ba09f2cdf..1f65aa387008 100644
--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -677,7 +677,6 @@ struct inode *ceph_alloc_inode(struct super_block *sb)
 	for (i = 0; i < CEPH_FILE_MODE_BITS; i++)
 		ci->i_nr_by_mode[i] = 0;
 
-	mutex_init(&ci->i_truncate_mutex);
 	ci->i_truncate_seq = 0;
 	ci->i_truncate_size = 0;
 	ci->i_truncate_pending = 0;
diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index 05452bc7eac1..35399689f0c1 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -466,7 +466,11 @@ struct ceph_inode_info {
 	unsigned long i_last_wr;
 	int i_nr_by_mode[CEPH_FILE_MODE_BITS];  /* open file counts */
 
-	struct mutex i_truncate_mutex;
+/* since i_fragtree_mutex is only used for directories and
+   i_truncate_mutex is only used for regular files, we use the same
+   field for both */
+#define i_truncate_mutex i_fragtree_mutex
+
 	u64 i_truncate_size;       /*  and the size we last truncated down to */
 	u32 i_truncate_seq;        /* last truncate to smaller size */
 	int i_truncate_pending;    /*  still need to call vmtruncate */
-- 
2.47.3