Here is a reworked version of my patch to ext3 to retry certain filesystem
operations after an ENOSPC error.  The ext3_should_retry_alloc() function will
not wait on the currently running transaction if there is a currently active
handle; hence this should avoid deadlocks in the Lustre use case.  The patch
is versus BK-recent.

I've also included a simple, reliable test case which demonstrates the problem
this patch is intended to fix.  (Note that BK-recent is not sufficient to
address this test case, and waiting on the commiting transaction in
ext3_new_block is also not sufficient.  Been there, tried that, didn't work.
We need to do the full-bore retry from the top level.  The
ext3_should_retry_alloc() will only wait on the committing transaction if
there is an active handle; hence Lustre will probably also need to use
ext3_should_retry_alloc() if it wants to reliably avoid this particular
problem.)

#!/bin/sh
#
#
TEST_DIR=/tmp
IMAGE=$TEST_DIR/retry.img
MNTPT=$TEST_DIR/retry.mnt
TEST_SRC=/usr/projects/e2fsprogs/e2fsprogs/build
MKE2FS_OPTS=""
IMAGE_SIZE=8192

umount $MNTPT
dd if=/dev/zero of=$IMAGE bs=4k count=$IMAGE_SIZE
mke2fs -j -F $MKE2FS_OPTS $IMAGE 

function test_log ()
{
	echo $*
	logger -p local4.notice $*
}

mkdir -p $MNTPT
mount -o loop -t ext3 $IMAGE $MNTPT
test_log Retry test: BEGIN
for i in `seq 1 3`
do
	test_log "Retry test: Loop $i"
	echo 2 > /proc/sys/fs/jbd-debug
	while ! mkdir -p $MNTPT/foo/bar
	do
		test_log "Retry test: mkdir failed"
		sleep 1
	done
	echo 0 > /proc/sys/fs/jbd-debug
	cp -r $TEST_SRC $MNTPT/foo/bar 2> /dev/null
	rm -rf $MNTPT/*
done
umount $MNTPT
test_log "Retry test: END"


akpm@osdl.org

  Rework the code to make it a formal JBD API entry point.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>