forked from luck/tmp_suning_uos_patched
[PATCH] Fix JBD race in t_forget list handling
Fix race between journal_commit_transaction() and other places as journal_unmap_buffer() that are adding buffers to transaction's t_forget list. We have to protect against such places by holding j_list_lock even when traversing the t_forget list. The fact that other places can only add buffers to the list makes the locking easier. OTOH the lock ranking complicates the stuff... Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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@ -720,11 +720,17 @@ void journal_commit_transaction(journal_t *journal)
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J_ASSERT(commit_transaction->t_log_list == NULL);
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restart_loop:
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/*
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* As there are other places (journal_unmap_buffer()) adding buffers
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* to this list we have to be careful and hold the j_list_lock.
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*/
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spin_lock(&journal->j_list_lock);
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while (commit_transaction->t_forget) {
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transaction_t *cp_transaction;
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struct buffer_head *bh;
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jh = commit_transaction->t_forget;
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spin_unlock(&journal->j_list_lock);
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bh = jh2bh(jh);
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jbd_lock_bh_state(bh);
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J_ASSERT_JH(jh, jh->b_transaction == commit_transaction ||
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@ -792,9 +798,25 @@ void journal_commit_transaction(journal_t *journal)
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journal_remove_journal_head(bh); /* needs a brelse */
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release_buffer_page(bh);
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}
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cond_resched_lock(&journal->j_list_lock);
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}
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spin_unlock(&journal->j_list_lock);
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/*
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* This is a bit sleazy. We borrow j_list_lock to protect
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* journal->j_committing_transaction in __journal_remove_checkpoint.
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* Really, __journal_remove_checkpoint should be using j_state_lock but
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* it's a bit hassle to hold that across __journal_remove_checkpoint
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*/
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spin_lock(&journal->j_state_lock);
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spin_lock(&journal->j_list_lock);
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/*
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* Now recheck if some buffers did not get attached to the transaction
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* while the lock was dropped...
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*/
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if (commit_transaction->t_forget) {
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spin_unlock(&journal->j_list_lock);
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if (cond_resched())
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goto restart_loop;
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spin_unlock(&journal->j_state_lock);
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goto restart_loop;
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}
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/* Done with this transaction! */
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@ -803,14 +825,6 @@ void journal_commit_transaction(journal_t *journal)
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J_ASSERT(commit_transaction->t_state == T_COMMIT);
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/*
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* This is a bit sleazy. We borrow j_list_lock to protect
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* journal->j_committing_transaction in __journal_remove_checkpoint.
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* Really, __jornal_remove_checkpoint should be using j_state_lock but
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* it's a bit hassle to hold that across __journal_remove_checkpoint
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*/
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spin_lock(&journal->j_state_lock);
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spin_lock(&journal->j_list_lock);
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commit_transaction->t_state = T_FINISHED;
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J_ASSERT(commit_transaction == journal->j_committing_transaction);
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journal->j_commit_sequence = commit_transaction->t_tid;
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