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author | Jan Kara <jack@suse.cz> | 2005-09-06 15:19:17 -0700 |
---|---|---|
committer | Linus Torvalds <torvalds@g5.osdl.org> | 2005-09-07 16:57:57 -0700 |
commit | 4407c2b6b297339e296facf62e020cf66e55053d (patch) | |
tree | 485d60b1cb5c6013d09a0327355e216b202bd8ed /fs | |
parent | e39f07c83bac96850265b87a69dfc5c90ed4f1f5 (diff) | |
download | linux-4407c2b6b297339e296facf62e020cf66e55053d.tar.gz linux-4407c2b6b297339e296facf62e020cf66e55053d.tar.bz2 linux-4407c2b6b297339e296facf62e020cf66e55053d.zip |
[PATCH] Fix race in do_get_write_access()
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>
Diffstat (limited to 'fs')
-rw-r--r-- | fs/jbd/transaction.c | 39 |
1 files changed, 21 insertions, 18 deletions
diff --git a/fs/jbd/transaction.c b/fs/jbd/transaction.c index 77b7662b840b..c6ec66fd8766 100644 --- a/fs/jbd/transaction.c +++ b/fs/jbd/transaction.c @@ -490,23 +490,21 @@ void journal_unlock_updates (journal_t *journal) */ static void jbd_unexpected_dirty_buffer(struct journal_head *jh) { - struct buffer_head *bh = jh2bh(jh); int jlist; - if (buffer_dirty(bh)) { - /* If this buffer is one which might reasonably be dirty - * --- ie. data, or not part of this journal --- then - * we're OK to leave it alone, but otherwise we need to - * move the dirty bit to the journal's own internal - * JBDDirty bit. */ - jlist = jh->b_jlist; - - if (jlist == BJ_Metadata || jlist == BJ_Reserved || - jlist == BJ_Shadow || jlist == BJ_Forget) { - if (test_clear_buffer_dirty(jh2bh(jh))) { - set_bit(BH_JBDDirty, &jh2bh(jh)->b_state); - } - } + /* If this buffer is one which might reasonably be dirty + * --- ie. data, or not part of this journal --- then + * we're OK to leave it alone, but otherwise we need to + * move the dirty bit to the journal's own internal + * JBDDirty bit. */ + jlist = jh->b_jlist; + + if (jlist == BJ_Metadata || jlist == BJ_Reserved || + jlist == BJ_Shadow || jlist == BJ_Forget) { + struct buffer_head *bh = jh2bh(jh); + + if (test_clear_buffer_dirty(bh)) + set_buffer_jbddirty(bh); } } @@ -574,9 +572,14 @@ repeat: if (jh->b_next_transaction) J_ASSERT_JH(jh, jh->b_next_transaction == transaction); - JBUFFER_TRACE(jh, "Unexpected dirty buffer"); - jbd_unexpected_dirty_buffer(jh); - } + } + /* + * In any case we need to clean the dirty flag and we must + * do it under the buffer lock to be sure we don't race + * with running write-out. + */ + JBUFFER_TRACE(jh, "Unexpected dirty buffer"); + jbd_unexpected_dirty_buffer(jh); } unlock_buffer(bh); |