[PATCH 2/2] ceph: pagecache writeback fault injection switch

[Jeff Layton]

From: Jeff Layton <jlay...@redhat.com>

Testing ceph for proper writeback error handling turns out to be quite
difficult. I tried using iptables to block traffic but that didn't
give reliable results.

I hacked in this wb_fault switch that makes the filesystem pretend that
writeback failed, even when it succeeds. With this, I could verify that
cephfs fsync error reporting does work properly.

Signed-off-by: Jeff Layton <jlay...@redhat.com>
---
 fs/ceph/addr.c    | 7 +++++++
 fs/ceph/debugfs.c | 8 +++++++-
 fs/ceph/super.h   | 2 ++
 3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index 50836280a6f8..a3831d100e16 100644
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -584,6 +584,10 @@ static int writepage_nounlock(struct page *page, struct 
writeback_control *wbc)
                                   page_off, len,
                                   truncate_seq, truncate_size,
                                   &inode->i_mtime, &page, 1);
+
+       if (fsc->wb_fault && err >= 0)
+               err = -EIO;
+
        if (err < 0) {
                struct writeback_control tmp_wbc;
                if (!wbc)
@@ -666,6 +670,9 @@ static void writepages_finish(struct ceph_osd_request *req)
        struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
        bool remove_page;
 
+       if (fsc->wb_fault && rc >= 0)
+               rc = -EIO;
+
        dout("writepages_finish %p rc %d\n", inode, rc);
        if (rc < 0) {
                mapping_set_error(mapping, rc);
diff --git a/fs/ceph/debugfs.c b/fs/ceph/debugfs.c
index 4e2d112c982f..e1e6eaa12031 100644
--- a/fs/ceph/debugfs.c
+++ b/fs/ceph/debugfs.c
@@ -197,7 +197,6 @@ CEPH_DEFINE_SHOW_FUNC(caps_show)
 CEPH_DEFINE_SHOW_FUNC(dentry_lru_show)
 CEPH_DEFINE_SHOW_FUNC(mds_sessions_show)
 
-
 /*
  * debugfs
  */
@@ -231,6 +230,7 @@ void ceph_fs_debugfs_cleanup(struct ceph_fs_client *fsc)
        debugfs_remove(fsc->debugfs_caps);
        debugfs_remove(fsc->debugfs_mdsc);
        debugfs_remove(fsc->debugfs_dentry_lru);
+       debugfs_remove(fsc->debugfs_wb_fault);
 }
 
 int ceph_fs_debugfs_init(struct ceph_fs_client *fsc)
@@ -298,6 +298,12 @@ int ceph_fs_debugfs_init(struct ceph_fs_client *fsc)
        if (!fsc->debugfs_dentry_lru)
                goto out;
 
+       fsc->debugfs_wb_fault = debugfs_create_bool("wb_fault",
+                                       0600, fsc->client->debugfs_dir,
+                                       &fsc->wb_fault);
+       if (!fsc->debugfs_wb_fault)
+               goto out;
+
        return 0;
 
 out:
diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index f02a2225fe42..a38fd6203b77 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -84,6 +84,7 @@ struct ceph_fs_client {
 
        unsigned long mount_state;
        int min_caps;                  /* min caps i added */
+       bool wb_fault;
 
        struct ceph_mds_client *mdsc;
 
@@ -100,6 +101,7 @@ struct ceph_fs_client {
        struct dentry *debugfs_bdi;
        struct dentry *debugfs_mdsc, *debugfs_mdsmap;
        struct dentry *debugfs_mds_sessions;
+       struct dentry *debugfs_wb_fault;
 #endif
 
 #ifdef CONFIG_CEPH_FSCACHE
-- 
2.13.3