tree 49e5a6f8041a7f0a9be0c1a39cd9088e3faa1df2
parent ea9947b4395fa34666086b2fa6f686e94903e047
author Chris Mason <chris.mason@oracle.com> 1336303427 -0400
committer Chris Mason <chris.mason@oracle.com> 1336303427 -0400

Btrfs: avoid sleeping in verify_parent_transid while atomic

verify_parent_transid needs to lock the extent range to make
sure no IO is underway, and so it can safely clear the
uptodate bits if our checks fail.

But, a few callers are using it with spinlocks held.  Most
of the time, the generation numbers are going to match, and
we don't want to switch to a blocking lock just for the error
case.  This adds an atomic flag to verify_parent_transid,
and changes it to return EAGAIN if it needs to block to
properly verifiy things.

Signed-off-by: Chris Mason <chris.mason@oracle.com>