GFS2: stuck in inode wait, no glocks stuck

This patch changes the lock ordering when gfs2 reclaims
unlinked dinodes, thereby avoiding a livelock.

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

1 files changed, 30 insertions, 48 deletions

diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
index 37391550284f..8bce73ed4d8e 100644
--- a/fs/gfs2/rgrp.c
+++ b/fs/gfs2/rgrp.c
@@ -952,16 +952,14 @@ static int try_rgrp_fit(struct gfs2_rgrpd *rgd, struct gfs2_alloc *al)
  *          The inode, if one has been found, in inode.
  */
 
-static int try_rgrp_unlink(struct gfs2_rgrpd *rgd, u64 *last_unlinked,
-                           u64 skip, struct inode **inode)
+static u64 try_rgrp_unlink(struct gfs2_rgrpd *rgd, u64 *last_unlinked,
+                           u64 skip)
 {
         u32 goal = 0, block;
         u64 no_addr;
         struct gfs2_sbd *sdp = rgd->rd_sbd;
         unsigned int n;
-        int error = 0;
 
-        *inode = NULL;
         for(;;) {
                 if (goal >= rgd->rd_data)
                         break;
@@ -981,10 +979,7 @@ static int try_rgrp_unlink(struct gfs2_rgrpd *rgd, u64 *last_unlinked,
                 if (no_addr == skip)
                         continue;
                 *last_unlinked = no_addr;
-                error = gfs2_unlinked_inode_lookup(rgd->rd_sbd->sd_vfs,
-                                                   no_addr, inode);
-                if (*inode || error)
-                        return error;
+                return no_addr;
         }
 
         rgd->rd_flags &= ~GFS2_RDF_CHECK;
@@ -1069,11 +1064,12 @@ static void forward_rgrp_set(struct gfs2_sbd *sdp, struct gfs2_rgrpd *rgd)
  * Try to acquire rgrp in way which avoids contending with others.
  *
  * Returns: errno
+ *          unlinked: the block address of an unlinked block to be reclaimed
  */
 
-static struct inode *get_local_rgrp(struct gfs2_inode *ip, u64 *last_unlinked)
+static int get_local_rgrp(struct gfs2_inode *ip, u64 *unlinked,
+                          u64 *last_unlinked)
 {
-        struct inode *inode = NULL;
         struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
         struct gfs2_rgrpd *rgd, *begin = NULL;
         struct gfs2_alloc *al = ip->i_alloc;
@@ -1082,6 +1078,7 @@ static struct inode *get_local_rgrp(struct gfs2_inode *ip, u64 *last_unlinked)
         int loops = 0;
         int error, rg_locked;
 
+        *unlinked = 0;
         rgd = gfs2_blk2rgrpd(sdp, ip->i_goal);
 
         while (rgd) {
@@ -1103,29 +1100,19 @@ static struct inode *get_local_rgrp(struct gfs2_inode *ip, u64 *last_unlinked)
                            because that would require an iput which can only
                            happen after the rgrp is unlocked. */
                         if (!rg_locked && rgd->rd_flags & GFS2_RDF_CHECK)
-                                error = try_rgrp_unlink(rgd, last_unlinked,
-                                                        ip->i_no_addr, &inode);
+                                *unlinked = try_rgrp_unlink(rgd, last_unlinked,
+                                                           ip->i_no_addr);
                         if (!rg_locked)
                                 gfs2_glock_dq_uninit(&al->al_rgd_gh);
-                        if (inode) {
-                                if (error) {
-                                        if (inode->i_state & I_NEW)
-                                                iget_failed(inode);
-                                        else
-                                                iput(inode);
-                                        return ERR_PTR(error);
-                                }
-                                return inode;
-                        }
-                        if (error)
-                                return ERR_PTR(error);
+                        if (*unlinked)
+                                return -EAGAIN;
                         /* fall through */
                 case GLR_TRYFAILED:
                         rgd = recent_rgrp_next(rgd);
                         break;
 
                 default:
-                        return ERR_PTR(error);
+                        return error;
                 }
         }
 
@@ -1148,22 +1135,12 @@ static struct inode *get_local_rgrp(struct gfs2_inode *ip, u64 *last_unlinked)
                         if (try_rgrp_fit(rgd, al))
                                 goto out;
                         if (!rg_locked && rgd->rd_flags & GFS2_RDF_CHECK)
-                                error = try_rgrp_unlink(rgd, last_unlinked,
-                                                        ip->i_no_addr, &inode);
+                                *unlinked = try_rgrp_unlink(rgd, last_unlinked,
+                                                            ip->i_no_addr);
                         if (!rg_locked)
                                 gfs2_glock_dq_uninit(&al->al_rgd_gh);
-                        if (inode) {
-                                if (error) {
-                                        if (inode->i_state & I_NEW)
-                                                iget_failed(inode);
-                                        else
-                                                iput(inode);
-                                        return ERR_PTR(error);
-                                }
-                                return inode;
-                        }
-                        if (error)
-                                return ERR_PTR(error);
+                        if (*unlinked)
+                                return -EAGAIN;
                         break;
 
                 case GLR_TRYFAILED:
@@ -1171,7 +1148,7 @@ static struct inode *get_local_rgrp(struct gfs2_inode *ip, u64 *last_unlinked)
                         break;
 
                 default:
-                        return ERR_PTR(error);
+                        return error;
                 }
 
                 rgd = gfs2_rgrpd_get_next(rgd);
@@ -1180,7 +1157,7 @@ static struct inode *get_local_rgrp(struct gfs2_inode *ip, u64 *last_unlinked)
 
                 if (rgd == begin) {
                         if (++loops >= 3)
-                                return ERR_PTR(-ENOSPC);
+                                return -ENOSPC;
                         if (!skipped)
                                 loops++;
                         flags = 0;
@@ -1200,7 +1177,7 @@ out:
                 forward_rgrp_set(sdp, rgd);
         }
 
-        return NULL;
+        return 0;
 }
 
 /**
@@ -1216,7 +1193,7 @@ int gfs2_inplace_reserve_i(struct gfs2_inode *ip, char *file, unsigned int line)
         struct gfs2_alloc *al = ip->i_alloc;
         struct inode *inode;
         int error = 0;
-        u64 last_unlinked = NO_BLOCK;
+        u64 last_unlinked = NO_BLOCK, unlinked;
 
         if (gfs2_assert_warn(sdp, al->al_requested))
                 return -EINVAL;
@@ -1232,14 +1209,19 @@ try_again:
         if (error)
                 return error;
 
-        inode = get_local_rgrp(ip, &last_unlinked);
-        if (inode) {
+        error = get_local_rgrp(ip, &unlinked, &last_unlinked);
+        if (error) {
                 if (ip != GFS2_I(sdp->sd_rindex))
                         gfs2_glock_dq_uninit(&al->al_ri_gh);
-                if (IS_ERR(inode))
-                        return PTR_ERR(inode);
-                iput(inode);
+                if (error != -EAGAIN)
+                        return error;
+                error = gfs2_unlinked_inode_lookup(ip->i_inode.i_sb,
+                                                   unlinked, &inode);
+                if (inode)
+                        iput(inode);
                 gfs2_log_flush(sdp, NULL);
+                if (error == GLR_TRYFAILED)
+                        error = 0;
                 goto try_again;
         }