ext4: Make ext4_get_blocks_wrap take the truncate_mutex early.

When doing a migrate from ext3 to ext4 inode we need to make sure the test
for inode type and walking inode data happens inside  lock. To make this
happen move truncate_mutex early before checking the i_flags.


This actually should enable us to remove the verify_chain().

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

2 files changed, 14 insertions, 64 deletions

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 8593e59020fe..ec5019fa552f 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -2129,6 +2129,10 @@ out:
         return err ? err : allocated;
 }
 
+/*
+ * Need to be called with
+ * mutex_lock(&EXT4_I(inode)->truncate_mutex);
+ */
 int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
                         ext4_lblk_t iblock,
                         unsigned long max_blocks, struct buffer_head *bh_result,
@@ -2144,7 +2148,6 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
         __clear_bit(BH_New, &bh_result->b_state);
         ext_debug("blocks %u/%lu requested for inode %u\n",
                         iblock, max_blocks, inode->i_ino);
-        mutex_lock(&EXT4_I(inode)->truncate_mutex);
 
         /* check in cache */
         goal = ext4_ext_in_cache(inode, iblock, &newex);
@@ -2318,8 +2321,6 @@ out2:
                 ext4_ext_drop_refs(path);
                 kfree(path);
         }
-        mutex_unlock(&EXT4_I(inode)->truncate_mutex);
-
         return err ? err : allocated;
 }
 
@@ -2449,6 +2450,7 @@ long ext4_fallocate(struct inode *inode, int mode, loff_t offset, loff_t len)
          * modify 1 super block, 1 block bitmap and 1 group descriptor.
          */
         credits = EXT4_DATA_TRANS_BLOCKS(inode->i_sb) + 3;
+        mutex_lock(&EXT4_I(inode)->truncate_mutex)
 retry:
         while (ret >= 0 && ret < max_blocks) {
                 block = block + ret;
@@ -2505,6 +2507,7 @@ retry:
         if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
                 goto retry;
 
+        mutex_unlock(&EXT4_I(inode)->truncate_mutex)
         /*
          * Time to update the file size.
          * Update only when preallocation was requested beyond the file size.
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index eaace1373ccb..71c7ad0c6723 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -243,13 +243,6 @@ static inline void add_chain(Indirect *p, struct buffer_head *bh, __le32 *v)
         p->bh = bh;
 }
 
-static int verify_chain(Indirect *from, Indirect *to)
-{
-        while (from <= to && from->key == *from->p)
-                from++;
-        return (from > to);
-}
-
 /**
  *      ext4_block_to_path - parse the block number into array of offsets
  *      @inode: inode in question (we are only interested in its superblock)
@@ -348,10 +341,11 @@ static int ext4_block_to_path(struct inode *inode,
  *              (pointer to last triple returned, *@err == 0)
  *      or when it gets an IO error reading an indirect block
  *              (ditto, *@err == -EIO)
- *      or when it notices that chain had been changed while it was reading
- *              (ditto, *@err == -EAGAIN)
  *      or when it reads all @depth-1 indirect blocks successfully and finds
  *      the whole chain, all way to the data (returns %NULL, *err == 0).
+ *
+ *      Need to be called with
+ *      mutex_lock(&EXT4_I(inode)->truncate_mutex)
  */
 static Indirect *ext4_get_branch(struct inode *inode, int depth,
                                  ext4_lblk_t  *offsets,
@@ -370,9 +364,6 @@ static Indirect *ext4_get_branch(struct inode *inode, int depth,
                 bh = sb_bread(sb, le32_to_cpu(p->key));
                 if (!bh)
                         goto failure;
-                /* Reader: pointers */
-                if (!verify_chain(chain, p))
-                        goto changed;
                 add_chain(++p, bh, (__le32*)bh->b_data + *++offsets);
                 /* Reader: end */
                 if (!p->key)
@@ -380,10 +371,6 @@ static Indirect *ext4_get_branch(struct inode *inode, int depth,
         }
         return NULL;
 
-changed:
-        brelse(bh);
-        *err = -EAGAIN;
-        goto no_block;
 failure:
         *err = -EIO;
 no_block:
@@ -787,6 +774,10 @@ err_out:
  * return > 0, # of blocks mapped or allocated.
  * return = 0, if plain lookup failed.
  * return < 0, error case.
+ *
+ *
+ * Need to be called with
+ * mutex_lock(&EXT4_I(inode)->truncate_mutex)
  */
 int ext4_get_blocks_handle(handle_t *handle, struct inode *inode,
                 ext4_lblk_t iblock, unsigned long maxblocks,
@@ -825,18 +816,6 @@ int ext4_get_blocks_handle(handle_t *handle, struct inode *inode,
                 while (count < maxblocks && count <= blocks_to_boundary) {
                         ext4_fsblk_t blk;
 
-                        if (!verify_chain(chain, partial)) {
-                                /*
-                                 * Indirect block might be removed by
-                                 * truncate while we were reading it.
-                                 * Handling of that case: forget what we've
-                                 * got now. Flag the err as EAGAIN, so it
-                                 * will reread.
-                                 */
-                                err = -EAGAIN;
-                                count = 0;
-                                break;
-                        }
                         blk = le32_to_cpu(*(chain[depth-1].p + count));
 
                         if (blk == first_block + count)
@@ -844,44 +823,13 @@ int ext4_get_blocks_handle(handle_t *handle, struct inode *inode,
                         else
                                 break;
                 }
-                if (err != -EAGAIN)
-                        goto got_it;
+                goto got_it;
         }
 
         /* Next simple case - plain lookup or failed read of indirect block */
         if (!create || err == -EIO)
                 goto cleanup;
 
-        mutex_lock(&ei->truncate_mutex);
-
-        /*
-         * If the indirect block is missing while we are reading
-         * the chain(ext4_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 = ext4_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
          * allocation info here if necessary
@@ -923,7 +871,6 @@ int ext4_get_blocks_handle(handle_t *handle, struct inode *inode,
         */
         if (!err && extend_disksize && inode->i_size > ei->i_disksize)
                 ei->i_disksize = inode->i_size;
-        mutex_unlock(&ei->truncate_mutex);
         if (err)
                 goto cleanup;