tree a65508f3456f623f51215581e3b00529a9c20ee7
parent b9e1d435fdf4ae0b925070d44b65d608f2707688
author Al Viro <viro@zeniv.linux.org.uk> 1461352004 -0400
committer Al Viro <viro@zeniv.linux.org.uk> 1462232845 -0400

make ext2_get_page() and friends work without external serialization

Right now ext2_get_page() (and its analogues in a bunch of other filesystems)
relies upon the directory being locked - the way it sets and tests Checked and
Error bits would be racy without that.  Switch to a slightly different scheme,
_not_ setting Checked in case of failure.  That way the logics becomes
	if Checked => OK
	else if Error => fail
	else if !validate => fail
	else => OK
with validation setting Checked or Error on success and failure resp. and
returning which one had happened.  Equivalent to the current logics, but unlike
the current logics not sensitive to the order of set_bit, test_bit getting
reordered by CPU, etc.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>