attached patch should fix the following race:
Proc 1 Proc 2
__flush_batch()
ll_rw_block()
do_get_write_access()
lock_buffer
jh is only waiting for checkpoint
-> b_transaction == NULL ->
do nothing
unlock_buffer
test_set_buffer_locked()
test_clear_buffer_dirty()
__journal_file_buffer()
change the data
submit_bh()
and we have sent wrong data to disk... We now clean the dirty buffer flag
under buffer lock in all cases and hence we know that whenever a buffer is
starting to be journaled we either finish the pending write-out before
attaching a buffer to a transaction or we won't write the buffer until the
transaction is going to be committed.
The test in jbd_unexpected_dirty_buffer() is redundant - remove it.
Furthermore we have to clear the buffer dirty bit under the buffer lock to
prevent races with buffer write-out (and hence prevent returning a buffer with
IO happening).
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This fixes the lots-of-fsx-linux-instances-cause-a-slow-leak bug.
It's been there since 2.6.6, caused by:
ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.5/2.6.5-mm4/broken-out/jbd-move-locked-buffers.patch
That patch moves under-writeout ordered-data buffers onto a separate journal
list during commit. It took out the old code which was based on a single
list.
The old code (necessarily) had logic which would restart I/O against buffers
which had been redirtied while they were on the committing transaction's
t_sync_datalist list. The new code only writes buffers once, ignoring
redirtyings by a later transaction, which is good.
But over on the truncate side of things, in journal_unmap_buffer(), we're
treating buffers on the t_locked_list as inviolable things which belong to the
committing transaction, and we just leave them alone during concurrent
truncate-vs-commit.
The net effect is that when truncate tries to invalidate a page whose buffers
are on t_locked_list and have been redirtied, journal_unmap_buffer() just
leaves those buffers alone. truncate will remove the page from its mapping
and we end up with an anonymous clean page with dirty buffers, which is an
illegal state for a page. The JBD commit will not clean those buffers as they
are removed from t_locked_list. The VM (try_to_free_buffers) cannot reclaim
these pages.
The patch teaches journal_unmap_buffer() about buffers which are on the
committing transaction's t_locked_list. These buffers have been written and
I/O has completed. We can take them off the transaction and undirty them
within the context of journal_invalidatepage()->journal_unmap_buffer().
Acked-by: "Stephen C. Tweedie" <sct@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Jan Kara