1 files changed, 33 insertions, 11 deletions

diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
index b43b9556366..acf67883110 100644
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c
@@ -590,9 +590,8 @@ static int ext2_get_blocks(struct inode *inode,
 
         if (depth == 0)
                 return (err);
-reread:
-        partial = ext2_get_branch(inode, depth, offsets, chain, &err);
 
+        partial = ext2_get_branch(inode, depth, offsets, chain, &err);
         /* Simplest case - block found, no allocation needed */
         if (!partial) {
                 first_block = le32_to_cpu(chain[depth - 1].key);
@@ -602,15 +601,16 @@ reread:
                 while (count < maxblocks && count <= blocks_to_boundary) {
                         ext2_fsblk_t blk;
 
-                        if (!verify_chain(chain, partial)) {
+                        if (!verify_chain(chain, chain + depth - 1)) {
                                 /*
                                  * Indirect block might be removed by
                                  * truncate while we were reading it.
                                  * Handling of that case: forget what we've
                                  * got now, go to reread.
                                  */
+                                err = -EAGAIN;
                                 count = 0;
-                                goto changed;
+                                break;
                         }
                         blk = le32_to_cpu(*(chain[depth-1].p + count));
                         if (blk == first_block + count)
@@ -618,7 +618,8 @@ reread:
                         else
                                 break;
                 }
-                goto got_it;
+                if (err != -EAGAIN)
+                        goto got_it;
         }
 
         /* Next simple case - plain lookup or failed read of indirect block */
@@ -626,6 +627,33 @@ reread:
                 goto cleanup;
 
         mutex_lock(&ei->truncate_mutex);
+        /*
+         * If the indirect block is missing while we are reading
+         * the chain(ext3_get_branch() returns -EAGAIN err), or
+         * if the chain has been changed after we grab the semaphore,
+         * (either because another process truncated this branch, or
+         * another get_block allocated this branch) re-grab the chain to see if
+         * the request block has been allocated or not.
+         *
+         * Since we already block the truncate/other get_block
+         * at this point, we will have the current copy of the chain when we
+         * splice the branch into the tree.
+         */
+        if (err == -EAGAIN || !verify_chain(chain, partial)) {
+                while (partial > chain) {
+                        brelse(partial->bh);
+                        partial--;
+                }
+                partial = ext2_get_branch(inode, depth, offsets, chain, &err);
+                if (!partial) {
+                        count++;
+                        mutex_unlock(&ei->truncate_mutex);
+                        if (err)
+                                goto cleanup;
+                        clear_buffer_new(bh_result);
+                        goto got_it;
+                }
+        }
 
         /*
          * Okay, we need to do block allocation.  Lazily initialize the block
@@ -683,12 +711,6 @@ cleanup:
                 partial--;
         }
         return err;
-changed:
-        while (partial > chain) {
-                brelse(partial->bh);
-                partial--;
-        }
-        goto reread;
 }
 
 int ext2_get_block(struct inode *inode, sector_t iblock, struct buffer_head *bh_result, int create)