GFS2: glock livelock

This patch fixes a couple gfs2 problems with the reclaiming of
unlinked dinodes.  First, there were a couple of livelocks where
everything would come to a halt waiting for a glock that was
seemingly held by a process that no longer existed.  In fact, the
process did exist, it just had the wrong pid number in the holder
information.  Second, there was a lock ordering problem between
inode locking and glock locking.  Third, glock/inode contention
could sometimes cause inodes to be improperly marked invalid by
iget_failed.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>

1 files changed, 92 insertions, 9 deletions

diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
index b1bf2694fb2b..51d8061fa07a 100644
--- a/fs/gfs2/inode.c
+++ b/fs/gfs2/inode.c
@@ -158,7 +158,6 @@ void gfs2_set_iop(struct inode *inode)
  * @sb: The super block
  * @no_addr: The inode number
  * @type: The type of the inode
- * @skip_freeing: set this not return an inode if it is currently being freed.
  *
  * Returns: A VFS inode, or an error
  */
@@ -166,17 +165,14 @@ void gfs2_set_iop(struct inode *inode)
 struct inode *gfs2_inode_lookup(struct super_block *sb,
                                 unsigned int type,
                                 u64 no_addr,
-                                u64 no_formal_ino, int skip_freeing)
+                                u64 no_formal_ino)
 {
         struct inode *inode;
         struct gfs2_inode *ip;
         struct gfs2_glock *io_gl;
         int error;
 
-        if (skip_freeing)
-                inode = gfs2_iget_skip(sb, no_addr);
-        else
-                inode = gfs2_iget(sb, no_addr);
+        inode = gfs2_iget(sb, no_addr);
         ip = GFS2_I(inode);
 
         if (!inode)
@@ -234,13 +230,100 @@ fail_glock:
 fail_iopen:
         gfs2_glock_put(io_gl);
 fail_put:
-        ip->i_gl->gl_object = NULL;
+        if (inode->i_state & I_NEW)
+                ip->i_gl->gl_object = NULL;
         gfs2_glock_put(ip->i_gl);
 fail:
-        iget_failed(inode);
+        if (inode->i_state & I_NEW)
+                iget_failed(inode);
+        else
+                iput(inode);
         return ERR_PTR(error);
 }
 
+/**
+ * gfs2_unlinked_inode_lookup - Lookup an unlinked inode for reclamation
+ * @sb: The super block
+ * no_addr: The inode number
+ * @@inode: A pointer to the inode found, if any
+ *
+ * Returns: 0 and *inode if no errors occurred.  If an error occurs,
+ *          the resulting *inode may or may not be NULL.
+ */
+
+int gfs2_unlinked_inode_lookup(struct super_block *sb, u64 no_addr,
+                               struct inode **inode)
+{
+        struct gfs2_sbd *sdp;
+        struct gfs2_inode *ip;
+        struct gfs2_glock *io_gl;
+        int error;
+        struct gfs2_holder gh;
+
+        *inode = gfs2_iget_skip(sb, no_addr);
+
+        if (!(*inode))
+                return -ENOBUFS;
+
+        if (!((*inode)->i_state & I_NEW))
+                return -ENOBUFS;
+
+        ip = GFS2_I(*inode);
+        sdp = GFS2_SB(*inode);
+        ip->i_no_formal_ino = -1;
+
+        error = gfs2_glock_get(sdp, no_addr, &gfs2_inode_glops, CREATE, &ip->i_gl);
+        if (unlikely(error))
+                goto fail;
+        ip->i_gl->gl_object = ip;
+
+        error = gfs2_glock_get(sdp, no_addr, &gfs2_iopen_glops, CREATE, &io_gl);
+        if (unlikely(error))
+                goto fail_put;
+
+        set_bit(GIF_INVALID, &ip->i_flags);
+        error = gfs2_glock_nq_init(io_gl, LM_ST_SHARED, LM_FLAG_TRY | GL_EXACT,
+                                   &ip->i_iopen_gh);
+        if (unlikely(error)) {
+                if (error == GLR_TRYFAILED)
+                        error = 0;
+                goto fail_iopen;
+        }
+        ip->i_iopen_gh.gh_gl->gl_object = ip;
+        gfs2_glock_put(io_gl);
+
+        (*inode)->i_mode = DT2IF(DT_UNKNOWN);
+
+        /*
+         * We must read the inode in order to work out its type in
+         * this case. Note that this doesn't happen often as we normally
+         * know the type beforehand. This code path only occurs during
+         * unlinked inode recovery (where it is safe to do this glock,
+         * which is not true in the general case).
+         */
+        error = gfs2_glock_nq_init(ip->i_gl, LM_ST_EXCLUSIVE, LM_FLAG_TRY,
+                                   &gh);
+        if (unlikely(error)) {
+                if (error == GLR_TRYFAILED)
+                        error = 0;
+                goto fail_glock;
+        }
+        /* Inode is now uptodate */
+        gfs2_glock_dq_uninit(&gh);
+        gfs2_set_iop(*inode);
+
+        return 0;
+fail_glock:
+        gfs2_glock_dq(&ip->i_iopen_gh);
+fail_iopen:
+        gfs2_glock_put(io_gl);
+fail_put:
+        ip->i_gl->gl_object = NULL;
+        gfs2_glock_put(ip->i_gl);
+fail:
+        return error;
+}
+
 static int gfs2_dinode_in(struct gfs2_inode *ip, const void *buf)
 {
         const struct gfs2_dinode *str = buf;
@@ -862,7 +945,7 @@ struct inode *gfs2_createi(struct gfs2_holder *ghs, const struct qstr *name,
                 goto fail_gunlock2;
 
         inode = gfs2_inode_lookup(dir->i_sb, IF2DT(mode), inum.no_addr,
-                                  inum.no_formal_ino, 0);
+                                  inum.no_formal_ino);
         if (IS_ERR(inode))
                 goto fail_gunlock2;