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author | Oleg Nesterov <oleg@redhat.com> | 2015-07-20 00:50:55 +0200 |
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committer | Oleg Nesterov <oleg@redhat.com> | 2015-08-15 13:52:09 +0200 |
commit | f4b554af9931585174d4913b482eacab75858964 (patch) | |
tree | e01977e85b9568688a28058ebacd82f34be6ae14 /fs/nfs | |
parent | bee9182d955227f01ff3b80c4cb6acca9bb40b11 (diff) | |
download | linux-f4b554af9931585174d4913b482eacab75858964.tar.bz2 |
fix the broken lockdep logic in __sb_start_write()
1. wait_event(frozen < level) without rwsem_acquire_read() is just
wrong from lockdep perspective. If we are going to deadlock
because the caller is buggy, lockdep can't detect this problem.
2. __sb_start_write() can race with thaw_super() + freeze_super(),
and after "goto retry" the 2nd acquire_freeze_lock() is wrong.
3. The "tell lockdep we are doing trylock" hack doesn't look nice.
I think this is correct, but this logic should be more explicit.
Yes, the recursive read_lock() is fine if we hold the lock on a
higher level. But we do not need to fool lockdep. If we can not
deadlock in this case then try-lock must not fail and we can use
use wait == F throughout this code.
Note: as Dave Chinner explains, the "trylock" hack and the fat comment
can be probably removed. But this needs a separate change and it will
be trivial: just kill __sb_start_write() and rename do_sb_start_write()
back to __sb_start_write().
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Jan Kara <jack@suse.com>
Diffstat (limited to 'fs/nfs')
0 files changed, 0 insertions, 0 deletions