[PATCH] ext3: remove unnecessary race then retry in ext3_get_block

[PATCH] ext3: remove unnecessary race then retry in ext3_get_block

The extra race-with-truncate-then-retry logic around
ext3_get_block_handle(), which was inherited from ext2, becomes unecessary
for ext3, since we have already obtained the ei->truncate_sem in
ext3_get_block_handle() before calling ext3_alloc_branch().  The
ei->truncate_sem is already there to block concurrent truncate and block
allocation on the same inode.  So the inode's indirect addressing tree
won't be changed after we grab that semaphore.

We could, after get the semaphore, re-verify the branch is up-to-date or
not.  If it has been changed, then get the updated branch.  If we still
need block allocation, we will have a safe version of the branch to work
with in the ext3_find_goal()/ext3_splice_branch().

The code becomes more readable after remove those retry logic.  The patch
also clean up some gotos in ext3_get_block_handle() to make it more
readable.

Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>