[RFC PATCH v2 09/10] ceph: cache layout in parent dir on first sync create

[Jeff Layton <jlayton@kernel.org>]

It doesn't do much good to do an asynchronous create unless we can do
I/O to it before the create reply comes in. That means we need layout
info the new file before we've gotten the response from the MDS.

All files created in a directory will initially inherit the same layout,
so copy off the requisite info from the first synchronous create in the
directory, and save it in a new i_cached_layout field. Zero out the
layout when we lose Dc caps in the dir.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 fs/ceph/caps.c  | 13 ++++++++++---
 fs/ceph/file.c  | 22 +++++++++++++++++++++-
 fs/ceph/inode.c |  2 ++
 fs/ceph/super.h |  1 +
 4 files changed, 34 insertions(+), 4 deletions(-)

diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index 9d1a3d6831f7..70bf50f00c27 100644
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -561,14 +561,14 @@ static void __cap_delay_cancel(struct ceph_mds_client *mdsc,
 	spin_unlock(&mdsc->cap_delay_lock);
 }
 
-/*
- * Common issue checks for add_cap, handle_cap_grant.
- */
+/* Common issue checks for add_cap, handle_cap_grant. */
 static void __check_cap_issue(struct ceph_inode_info *ci, struct ceph_cap *cap,
 			      unsigned issued)
 {
 	unsigned had = __ceph_caps_issued(ci, NULL);
 
+	lockdep_assert_held(&ci->i_ceph_lock);
+
 	/*
 	 * Each time we receive FILE_CACHE anew, we increment
 	 * i_rdcache_gen.
@@ -593,6 +593,13 @@ static void __check_cap_issue(struct ceph_inode_info *ci, struct ceph_cap *cap,
 			__ceph_dir_clear_complete(ci);
 		}
 	}
+
+	/* Wipe saved layout if we're losing DIR_CREATE caps */
+	if (S_ISDIR(ci->vfs_inode.i_mode) && (had & CEPH_CAP_DIR_CREATE) &&
+		!(issued & CEPH_CAP_DIR_CREATE)) {
+	     ceph_put_string(rcu_dereference_raw(ci->i_cached_layout.pool_ns));
+	     memset(&ci->i_cached_layout, 0, sizeof(ci->i_cached_layout));
+	}
 }
 
 /*
diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index 1e6cdf2dfe90..b44ccbc85fe4 100644
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -430,6 +430,23 @@ int ceph_open(struct inode *inode, struct file *file)
 	return err;
 }
 
+/* Clone the layout from a synchronous create, if the dir now has Dc caps */
+static void
+cache_file_layout(struct inode *dst, struct inode *src)
+{
+	struct ceph_inode_info *cdst = ceph_inode(dst);
+	struct ceph_inode_info *csrc = ceph_inode(src);
+
+	spin_lock(&cdst->i_ceph_lock);
+	if ((__ceph_caps_issued(cdst, NULL) & CEPH_CAP_DIR_CREATE) &&
+	    !ceph_file_layout_is_valid(&cdst->i_cached_layout)) {
+		memcpy(&cdst->i_cached_layout, &csrc->i_layout,
+			sizeof(cdst->i_cached_layout));
+		rcu_assign_pointer(cdst->i_cached_layout.pool_ns,
+				   ceph_try_get_string(csrc->i_layout.pool_ns));
+	}
+	spin_unlock(&cdst->i_ceph_lock);
+}
 
 /*
  * Do a lookup + open with a single request.  If we get a non-existent
@@ -518,7 +535,10 @@ int ceph_atomic_open(struct inode *dir, struct dentry *dentry,
 	} else {
 		dout("atomic_open finish_open on dn %p\n", dn);
 		if (req->r_op == CEPH_MDS_OP_CREATE && req->r_reply_info.has_create_ino) {
-			ceph_init_inode_acls(d_inode(dentry), &as_ctx);
+			struct inode *newino = d_inode(dentry);
+
+			cache_file_layout(dir, newino);
+			ceph_init_inode_acls(newino, &as_ctx);
 			file->f_mode |= FMODE_CREATED;
 		}
 		err = finish_open(file, dentry, ceph_open);
diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
index 4056c7968b86..73f986efb1fd 100644
--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -447,6 +447,7 @@ struct inode *ceph_alloc_inode(struct super_block *sb)
 	ci->i_max_files = 0;
 
 	memset(&ci->i_dir_layout, 0, sizeof(ci->i_dir_layout));
+	memset(&ci->i_cached_layout, 0, sizeof(ci->i_cached_layout));
 	RCU_INIT_POINTER(ci->i_layout.pool_ns, NULL);
 
 	ci->i_fragtree = RB_ROOT;
@@ -587,6 +588,7 @@ void ceph_evict_inode(struct inode *inode)
 		ceph_buffer_put(ci->i_xattrs.prealloc_blob);
 
 	ceph_put_string(rcu_dereference_raw(ci->i_layout.pool_ns));
+	ceph_put_string(rcu_dereference_raw(ci->i_cached_layout.pool_ns));
 }
 
 static inline blkcnt_t calc_inode_blocks(u64 size)
diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index 86dd4a2163e0..09bd4b71de91 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -326,6 +326,7 @@ struct ceph_inode_info {
 
 	struct ceph_dir_layout i_dir_layout;
 	struct ceph_file_layout i_layout;
+	struct ceph_file_layout i_cached_layout;	// for async creates
 	char *i_symlink;
 
 	/* for dirs */
-- 
2.24.1