1 files changed, 61 insertions, 83 deletions

diff --git a/fs/ext3/inode.c b/fs/ext3/inode.c
index 040eb288bb1c..ea5888688f94 100644
--- a/fs/ext3/inode.c
+++ b/fs/ext3/inode.c
@@ -455,12 +455,11 @@ static unsigned long ext3_find_near(struct inode *inode, Indirect *ind)
  *      @goal:  place to store the result.
  *
  *      Normally this function find the prefered place for block allocation,
- *      stores it in *@goal and returns zero. If the branch had been changed
- *      under us we return -EAGAIN.
+ *      stores it in *@goal and returns zero.
  */
 
-static int ext3_find_goal(struct inode *inode, long block, Indirect chain[4],
-                          Indirect *partial, unsigned long *goal)
+static unsigned long ext3_find_goal(struct inode *inode, long block,
+                Indirect chain[4], Indirect *partial)
 {
         struct ext3_block_alloc_info *block_i =  EXT3_I(inode)->i_block_alloc_info;
 
@@ -470,15 +469,10 @@ static int ext3_find_goal(struct inode *inode, long block, Indirect chain[4],
          */
         if (block_i && (block == block_i->last_alloc_logical_block + 1)
                 && (block_i->last_alloc_physical_block != 0)) {
-                *goal = block_i->last_alloc_physical_block + 1;
-                return 0;
+                return block_i->last_alloc_physical_block + 1;
         }
 
-        if (verify_chain(chain, partial)) {
-                *goal = ext3_find_near(inode, partial);
-                return 0;
-        }
-        return -EAGAIN;
+        return ext3_find_near(inode, partial);
 }
 
 /**
@@ -582,12 +576,9 @@ static int ext3_alloc_branch(handle_t *handle, struct inode *inode,
  *      @where: location of missing link
  *      @num:   number of blocks we are adding
  *
- *      This function verifies that chain (up to the missing link) had not
- *      changed, fills the missing link and does all housekeeping needed in
+ *      This function fills the missing link and does all housekeeping needed in
  *      inode (->i_blocks, etc.). In case of success we end up with the full
- *      chain to new block and return 0. Otherwise (== chain had been changed)
- *      we free the new blocks (forgetting their buffer_heads, indeed) and
- *      return -EAGAIN.
+ *      chain to new block and return 0.
  */
 
 static int ext3_splice_branch(handle_t *handle, struct inode *inode, long block,
@@ -608,12 +599,6 @@ static int ext3_splice_branch(handle_t *handle, struct inode *inode, long block,
                 if (err)
                         goto err_out;
         }
-        /* Verify that place we are splicing to is still there and vacant */
-
-        if (!verify_chain(chain, where-1) || *where->p)
-                /* Writer: end */
-                goto changed;
-
         /* That's it */
 
         *where->p = where->key;
@@ -657,26 +642,11 @@ static int ext3_splice_branch(handle_t *handle, struct inode *inode, long block,
         }
         return err;
 
-changed:
-        /*
-         * AKPM: if where[i].bh isn't part of the current updating
-         * transaction then we explode nastily.  Test this code path.
-         */
-        jbd_debug(1, "the chain changed: try again\n");
-        err = -EAGAIN;
-
 err_out:
         for (i = 1; i < num; i++) {
                 BUFFER_TRACE(where[i].bh, "call journal_forget");
                 ext3_journal_forget(handle, where[i].bh);
         }
-        /* For the normal collision cleanup case, we free up the blocks.
-         * On genuine filesystem errors we don't even think about doing
-         * that. */
-        if (err == -EAGAIN)
-                for (i = 0; i < num; i++)
-                        ext3_free_blocks(handle, inode, 
-                                         le32_to_cpu(where[i].key), 1);
         return err;
 }
 
@@ -708,7 +678,7 @@ ext3_get_block_handle(handle_t *handle, struct inode *inode, sector_t iblock,
         unsigned long goal;
         int left;
         int boundary = 0;
-        int depth = ext3_block_to_path(inode, iblock, offsets, &boundary);
+        const int depth = ext3_block_to_path(inode, iblock, offsets, &boundary);
         struct ext3_inode_info *ei = EXT3_I(inode);
 
         J_ASSERT(handle != NULL || create == 0);
@@ -716,54 +686,55 @@ ext3_get_block_handle(handle_t *handle, struct inode *inode, sector_t iblock,
         if (depth == 0)
                 goto out;
 
-reread:
         partial = ext3_get_branch(inode, depth, offsets, chain, &err);
 
         /* Simplest case - block found, no allocation needed */
         if (!partial) {
                 clear_buffer_new(bh_result);
-got_it:
-                map_bh(bh_result, inode->i_sb, le32_to_cpu(chain[depth-1].key));
-                if (boundary)
-                        set_buffer_boundary(bh_result);
-                /* Clean up and exit */
-                partial = chain+depth-1; /* the whole chain */
-                goto cleanup;
+                goto got_it;
         }
 
         /* Next simple case - plain lookup or failed read of indirect block */
-        if (!create || err == -EIO) {
-cleanup:
+        if (!create || err == -EIO)
+                goto cleanup;
+
+        down(&ei->truncate_sem);
+
+        /*
+         * 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) {
-                        BUFFER_TRACE(partial->bh, "call brelse");
                         brelse(partial->bh);
                         partial--;
                 }
-                BUFFER_TRACE(bh_result, "returned");
-out:
-                return err;
+                partial = ext3_get_branch(inode, depth, offsets, chain, &err);
+                if (!partial) {
+                        up(&ei->truncate_sem);
+                        if (err)
+                                goto cleanup;
+                        clear_buffer_new(bh_result);
+                        goto got_it;
+                }
         }
 
         /*
-         * Indirect block might be removed by truncate while we were
-         * reading it. Handling of that case (forget what we've got and
-         * reread) is taken out of the main path.
-         */
-        if (err == -EAGAIN)
-                goto changed;
-
-        goal = 0;
-        down(&ei->truncate_sem);
-
-        /* lazy initialize the block allocation info here if necessary */
-        if (S_ISREG(inode->i_mode) && (!ei->i_block_alloc_info)) {
+         * Okay, we need to do block allocation.  Lazily initialize the block
+         * allocation info here if necessary
+        */
+        if (S_ISREG(inode->i_mode) && (!ei->i_block_alloc_info))
                 ext3_init_block_alloc_info(inode);
-        }
 
-        if (ext3_find_goal(inode, iblock, chain, partial, &goal) < 0) {
-                up(&ei->truncate_sem);
-                goto changed;
-        }
+        goal = ext3_find_goal(inode, iblock, chain, partial);
 
         left = (chain + depth) - partial;
 
@@ -771,38 +742,45 @@ out:
          * Block out ext3_truncate while we alter the tree
          */
         err = ext3_alloc_branch(handle, inode, left, goal,
-                                        offsets+(partial-chain), partial);
+                                offsets + (partial - chain), partial);
 
-        /* The ext3_splice_branch call will free and forget any buffers
+        /*
+         * The ext3_splice_branch call will free and forget any buffers
          * on the new chain if there is a failure, but that risks using
          * up transaction credits, especially for bitmaps where the
          * credits cannot be returned.  Can we handle this somehow?  We
-         * may need to return -EAGAIN upwards in the worst case.  --sct */
+         * may need to return -EAGAIN upwards in the worst case.  --sct
+         */
         if (!err)
                 err = ext3_splice_branch(handle, inode, iblock, chain,
                                          partial, left);
-        /* i_disksize growing is protected by truncate_sem
-         * don't forget to protect it if you're about to implement
-         * concurrent ext3_get_block() -bzzz */
+        /*
+         * i_disksize growing is protected by truncate_sem.  Don't forget to
+         * protect it if you're about to implement concurrent
+         * ext3_get_block() -bzzz
+        */
         if (!err && extend_disksize && inode->i_size > ei->i_disksize)
                 ei->i_disksize = inode->i_size;
         up(&ei->truncate_sem);
-        if (err == -EAGAIN)
-                goto changed;
         if (err)
                 goto cleanup;
 
         set_buffer_new(bh_result);
-        goto got_it;
-
-changed:
+got_it:
+        map_bh(bh_result, inode->i_sb, le32_to_cpu(chain[depth-1].key));
+        if (boundary)
+                set_buffer_boundary(bh_result);
+        /* Clean up and exit */
+        partial = chain + depth - 1;    /* the whole chain */
+cleanup:
         while (partial > chain) {
-                jbd_debug(1, "buffer chain changed, retrying\n");
-                BUFFER_TRACE(partial->bh, "brelsing");
+                BUFFER_TRACE(partial->bh, "call brelse");
                 brelse(partial->bh);
                 partial--;
         }
-        goto reread;
+        BUFFER_TRACE(bh_result, "returned");
+out:
+        return err;
 }
 
 static int ext3_get_block(struct inode *inode, sector_t iblock,