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authorJan Kara <jack@suse.cz>2005-09-06 18:19:17 -0400
committerLinus Torvalds <torvalds@g5.osdl.org>2005-09-07 19:57:57 -0400
commit4407c2b6b297339e296facf62e020cf66e55053d (patch)
tree485d60b1cb5c6013d09a0327355e216b202bd8ed /fs/jbd/transaction.c
parente39f07c83bac96850265b87a69dfc5c90ed4f1f5 (diff)
[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/jbd/transaction.c')
-rw-r--r--fs/jbd/transaction.c39
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)
490 */ 490 */
491static void jbd_unexpected_dirty_buffer(struct journal_head *jh) 491static void jbd_unexpected_dirty_buffer(struct journal_head *jh)
492{ 492{
493 struct buffer_head *bh = jh2bh(jh);
494 int jlist; 493 int jlist;
495 494
496 if (buffer_dirty(bh)) { 495 /* If this buffer is one which might reasonably be dirty
497 /* If this buffer is one which might reasonably be dirty 496 * --- ie. data, or not part of this journal --- then
498 * --- ie. data, or not part of this journal --- then 497 * we're OK to leave it alone, but otherwise we need to
499 * we're OK to leave it alone, but otherwise we need to 498 * move the dirty bit to the journal's own internal
500 * move the dirty bit to the journal's own internal 499 * JBDDirty bit. */
501 * JBDDirty bit. */ 500 jlist = jh->b_jlist;
502 jlist = jh->b_jlist; 501
503 502 if (jlist == BJ_Metadata || jlist == BJ_Reserved ||
504 if (jlist == BJ_Metadata || jlist == BJ_Reserved || 503 jlist == BJ_Shadow || jlist == BJ_Forget) {
505 jlist == BJ_Shadow || jlist == BJ_Forget) { 504 struct buffer_head *bh = jh2bh(jh);
506 if (test_clear_buffer_dirty(jh2bh(jh))) { 505
507 set_bit(BH_JBDDirty, &jh2bh(jh)->b_state); 506 if (test_clear_buffer_dirty(bh))
508 } 507 set_buffer_jbddirty(bh);
509 }
510 } 508 }
511} 509}
512 510
@@ -574,9 +572,14 @@ repeat:
574 if (jh->b_next_transaction) 572 if (jh->b_next_transaction)
575 J_ASSERT_JH(jh, jh->b_next_transaction == 573 J_ASSERT_JH(jh, jh->b_next_transaction ==
576 transaction); 574 transaction);
577 JBUFFER_TRACE(jh, "Unexpected dirty buffer"); 575 }
578 jbd_unexpected_dirty_buffer(jh); 576 /*
579 } 577 * In any case we need to clean the dirty flag and we must
578 * do it under the buffer lock to be sure we don't race
579 * with running write-out.
580 */
581 JBUFFER_TRACE(jh, "Unexpected dirty buffer");
582 jbd_unexpected_dirty_buffer(jh);
580 } 583 }
581 584
582 unlock_buffer(bh); 585 unlock_buffer(bh);