[GFS2] Recovery for lost unlinked inodes

Under certain circumstances its possible (though rather unlikely) that
inodes which were unlinked by one node while still open on another might
get "lost" in the sense that they don't get deallocated if the node
which held the inode open crashed before it was unlinked.

This patch adds the recovery code which allows automatic deallocation of
the inode if its found during block allocation (the sensible time to
look for such inodes since we are scanning the rgrp's bitmaps anyway at
this time, so it adds no overhead to do this).

Since the inode will have had its i_nlink set to zero, all we need to
trigger recovery is a lookup and an iput(), and the normal deallocation
code takes care of the rest.

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

1 files changed, 70 insertions, 17 deletions

diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
index 027f6ec5b0d9..fd3fd9074779 100644
--- a/fs/gfs2/rgrp.c
+++ b/fs/gfs2/rgrp.c
@@ -28,6 +28,7 @@
 #include "ops_file.h"
 #include "util.h"
 #include "log.h"
+#include "inode.h"
 
 #define BFITNOENT ((u32)~0)
 
@@ -50,6 +51,9 @@ static const char valid_change[16] = {
                 1, 0, 0, 0
 };
 
+static u32 rgblk_search(struct gfs2_rgrpd *rgd, u32 goal,
+                        unsigned char old_state, unsigned char new_state);
+
 /**
  * gfs2_setbit - Set a bit in the bitmaps
  * @buffer: the buffer that holds the bitmaps
@@ -531,6 +535,7 @@ static int read_rindex_entry(struct gfs2_inode *ip,
 
         rgd->rd_gl->gl_object = rgd;
         rgd->rd_rg_vn = rgd->rd_gl->gl_vn - 1;
+        rgd->rd_flags |= GFS2_RDF_CHECK;
         return error;
 }
 
@@ -846,6 +851,37 @@ static int try_rgrp_fit(struct gfs2_rgrpd *rgd, struct gfs2_alloc *al)
 }
 
 /**
+ * try_rgrp_unlink - Look for any unlinked, allocated, but unused inodes
+ * @rgd: The rgrp
+ *
+ * Returns: The inode, if one has been found
+ */
+
+static struct inode *try_rgrp_unlink(struct gfs2_rgrpd *rgd, u64 *last_unlinked)
+{
+        struct inode *inode;
+        u32 goal = 0;
+        u64 ino;
+
+        for(;;) {
+                goal = rgblk_search(rgd, goal, GFS2_BLKST_UNLINKED,
+                                    GFS2_BLKST_UNLINKED);
+                if (goal == 0)
+                        return 0;
+                ino = goal + rgd->rd_data0;
+                if (ino <= *last_unlinked)
+                        continue;
+                *last_unlinked = ino;
+                inode = gfs2_inode_lookup(rgd->rd_sbd->sd_vfs, ino, DT_UNKNOWN);
+                if (!IS_ERR(inode))
+                        return inode;
+        }
+
+        rgd->rd_flags &= ~GFS2_RDF_CHECK;
+        return NULL;
+}
+
+/**
  * recent_rgrp_first - get first RG from "recent" list
  * @sdp: The GFS2 superblock
  * @rglast: address of the rgrp used last
@@ -1006,8 +1042,9 @@ static void forward_rgrp_set(struct gfs2_sbd *sdp, struct gfs2_rgrpd *rgd)
  * Returns: errno
  */
 
-static int get_local_rgrp(struct gfs2_inode *ip)
+static struct inode *get_local_rgrp(struct gfs2_inode *ip, 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;
@@ -1027,7 +1064,11 @@ static int get_local_rgrp(struct gfs2_inode *ip)
                 case 0:
                         if (try_rgrp_fit(rgd, al))
                                 goto out;
+                        if (rgd->rd_flags & GFS2_RDF_CHECK)
+                                inode = try_rgrp_unlink(rgd, last_unlinked);
                         gfs2_glock_dq_uninit(&al->al_rgd_gh);
+                        if (inode)
+                                return inode;
                         rgd = recent_rgrp_next(rgd, 1);
                         break;
 
@@ -1036,7 +1077,7 @@ static int get_local_rgrp(struct gfs2_inode *ip)
                         break;
 
                 default:
-                        return error;
+                        return ERR_PTR(error);
                 }
         }
 
@@ -1051,7 +1092,11 @@ static int get_local_rgrp(struct gfs2_inode *ip)
                 case 0:
                         if (try_rgrp_fit(rgd, al))
                                 goto out;
+                        if (rgd->rd_flags & GFS2_RDF_CHECK)
+                                inode = try_rgrp_unlink(rgd, last_unlinked);
                         gfs2_glock_dq_uninit(&al->al_rgd_gh);
+                        if (inode)
+                                return inode;
                         break;
 
                 case GLR_TRYFAILED:
@@ -1059,7 +1104,7 @@ static int get_local_rgrp(struct gfs2_inode *ip)
                         break;
 
                 default:
-                        return error;
+                        return ERR_PTR(error);
                 }
 
                 rgd = gfs2_rgrpd_get_next(rgd);
@@ -1068,7 +1113,7 @@ static int get_local_rgrp(struct gfs2_inode *ip)
 
                 if (rgd == begin) {
                         if (++loops >= 3)
-                                return -ENOSPC;
+                                return ERR_PTR(-ENOSPC);
                         if (!skipped)
                                 loops++;
                         flags = 0;
@@ -1088,7 +1133,7 @@ out:
                 forward_rgrp_set(sdp, rgd);
         }
 
-        return 0;
+        return NULL;
 }
 
 /**
@@ -1102,11 +1147,14 @@ int gfs2_inplace_reserve_i(struct gfs2_inode *ip, char *file, unsigned int line)
 {
         struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
         struct gfs2_alloc *al = &ip->i_alloc;
+        struct inode *inode;
         int error = 0;
+        u64 last_unlinked = 0;
 
         if (gfs2_assert_warn(sdp, al->al_requested))
                 return -EINVAL;
 
+try_again:
         /* We need to hold the rindex unless the inode we're using is
            the rindex itself, in which case it's already held. */
         if (ip != GFS2_I(sdp->sd_rindex))
@@ -1117,11 +1165,15 @@ int gfs2_inplace_reserve_i(struct gfs2_inode *ip, char *file, unsigned int line)
         if (error)
                 return error;
 
-        error = get_local_rgrp(ip);
-        if (error) {
+        inode = get_local_rgrp(ip, &last_unlinked);
+        if (inode) {
                 if (ip != GFS2_I(sdp->sd_rindex))
                         gfs2_glock_dq_uninit(&al->al_ri_gh);
-                return error;
+                if (IS_ERR(inode))
+                        return PTR_ERR(inode);
+                iput(inode);
+                gfs2_log_flush(sdp, NULL);
+                goto try_again;
         }
 
         al->al_file = file;
@@ -1209,7 +1261,7 @@ unsigned char gfs2_get_block_type(struct gfs2_rgrpd *rgd, u64 block)
  */
 
 static u32 rgblk_search(struct gfs2_rgrpd *rgd, u32 goal,
-                             unsigned char old_state, unsigned char new_state)
+                        unsigned char old_state, unsigned char new_state)
 {
         struct gfs2_bitmap *bi = NULL;
         u32 length = rgd->rd_length;
@@ -1250,17 +1302,18 @@ static u32 rgblk_search(struct gfs2_rgrpd *rgd, u32 goal,
                 goal = 0;
         }
 
-        if (gfs2_assert_withdraw(rgd->rd_sbd, x <= length))
-                blk = 0;
+        if (old_state != new_state) {
+                gfs2_assert_withdraw(rgd->rd_sbd, blk != BFITNOENT);
 
-        gfs2_trans_add_bh(rgd->rd_gl, bi->bi_bh, 1);
-        gfs2_setbit(rgd, bi->bi_bh->b_data + bi->bi_offset,
-                    bi->bi_len, blk, new_state);
-        if (bi->bi_clone)
-                gfs2_setbit(rgd, bi->bi_clone + bi->bi_offset,
+                gfs2_trans_add_bh(rgd->rd_gl, bi->bi_bh, 1);
+                gfs2_setbit(rgd, bi->bi_bh->b_data + bi->bi_offset,
                             bi->bi_len, blk, new_state);
+                if (bi->bi_clone)
+                        gfs2_setbit(rgd, bi->bi_clone + bi->bi_offset,
+                                    bi->bi_len, blk, new_state);
+        }
 
-        return bi->bi_start * GFS2_NBBY + blk;
+        return (blk == BFITNOENT) ? 0 : (bi->bi_start * GFS2_NBBY) + blk;
 }
 
 /**