Il 14/08/2012 07:01, liub.liubo@xxxxxxxxx ha scritto:
From: Liu Bo <bo.li.liu@xxxxxxxxxx>
I found this while testing xfstests 068, the story is
t1 t2
sys_sync thaw_super
iterate_supers
down_read(sb->s_umount) down_write(sb->s_umount) --->wait for t1
sync_fs (with wait mode)
start_transaction
sb_start_intwrite --------------------> wait for t2 to set s_writers.frozen to SB_UNFROZEN
In this patch, I add an helper sb_start_intwrite_trylock() and use it before we
start_transaction in sync_fs() with wait mode so that we won't hit the deadlock.
IMHO, we should avoid to call the sync operation on a frozen fs. The
freeze operation, indeed, already include a sync operation. According to
man page, no other operation should modify the fs after the freeze. So
for me the modification is inside sync_filesystem (and sync_one_sb).
Marco
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