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jbd: Fix oops in journal_remove_journal_head()
journal_remove_journal_head() can oops when trying to access journal_head
returned by bh2jh(). This is caused for example by the following race:
TASK1 TASK2
journal_commit_transaction()
...
processing t_forget list
__journal_refile_buffer(jh);
if (!jh->b_transaction) {
jbd_unlock_bh_state(bh);
journal_try_to_free_buffers()
journal_grab_journal_head(bh)
jbd_lock_bh_state(bh)
__journal_try_to_free_buffer()
journal_put_journal_head(jh)
journal_remove_journal_head(bh);
journal_put_journal_head() in TASK2 sees that b_jcount == 0 and buffer is not
part of any transaction and thus frees journal_head before TASK1 gets to doing
so. Note that even buffer_head can be released by try_to_free_buffers() after
journal_put_journal_head() which adds even larger opportunity for oops (but I
didn't see this happen in reality).
Fix the problem by making transactions hold their own journal_head reference
(in b_jcount). That way we don't have to remove journal_head explicitely via
journal_remove_journal_head() and instead just remove journal_head when
b_jcount drops to zero. The result of this is that [__]journal_refile_buffer(),
[__]journal_unfile_buffer(), and __journal_remove_checkpoint() can free
journal_head which needs modification of a few callers. Also we have to be
careful because once journal_head is removed, buffer_head might be freed as
well. So we have to get our own buffer_head reference where it matters.
Signed-off-by: Jan Kara <jack@suse.cz>
This commit is contained in:
Jan Kara
parent
2c2ea9451f
commit
bb189247f3
@ -96,10 +96,14 @@ static int __try_to_free_cp_buf(struct journal_head *jh)
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if (jh->b_jlist == BJ_None && !buffer_locked(bh) &&
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!buffer_dirty(bh) && !buffer_write_io_error(bh)) {
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/*
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* Get our reference so that bh cannot be freed before
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* we unlock it
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*/
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get_bh(bh);
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JBUFFER_TRACE(jh, "remove from checkpoint list");
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ret = __journal_remove_checkpoint(jh) + 1;
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jbd_unlock_bh_state(bh);
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journal_remove_journal_head(bh);
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BUFFER_TRACE(bh, "release");
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__brelse(bh);
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} else {
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@ -221,8 +225,8 @@ restart:
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spin_lock(&journal->j_list_lock);
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goto restart;
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}
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get_bh(bh);
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if (buffer_locked(bh)) {
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get_bh(bh);
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spin_unlock(&journal->j_list_lock);
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jbd_unlock_bh_state(bh);
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wait_on_buffer(bh);
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@ -241,7 +245,6 @@ restart:
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*/
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released = __journal_remove_checkpoint(jh);
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jbd_unlock_bh_state(bh);
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journal_remove_journal_head(bh);
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__brelse(bh);
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}
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@ -305,12 +308,12 @@ static int __process_buffer(journal_t *journal, struct journal_head *jh,
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ret = 1;
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if (unlikely(buffer_write_io_error(bh)))
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ret = -EIO;
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get_bh(bh);
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J_ASSERT_JH(jh, !buffer_jbddirty(bh));
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BUFFER_TRACE(bh, "remove from checkpoint");
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__journal_remove_checkpoint(jh);
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spin_unlock(&journal->j_list_lock);
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jbd_unlock_bh_state(bh);
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journal_remove_journal_head(bh);
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__brelse(bh);
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} else {
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/*
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@ -526,9 +529,9 @@ int cleanup_journal_tail(journal_t *journal)
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/*
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* journal_clean_one_cp_list
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*
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* Find all the written-back checkpoint buffers in the given list and release them.
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* Find all the written-back checkpoint buffers in the given list and release
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* them.
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*
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* Called with the journal locked.
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* Called with j_list_lock held.
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* Returns number of bufers reaped (for debug)
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*/
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@ -635,8 +638,8 @@ out:
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* checkpoint lists.
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*
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* The function returns 1 if it frees the transaction, 0 otherwise.
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* The function can free jh and bh.
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*
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* This function is called with the journal locked.
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* This function is called with j_list_lock held.
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* This function is called with jbd_lock_bh_state(jh2bh(jh))
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*/
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@ -655,13 +658,14 @@ int __journal_remove_checkpoint(struct journal_head *jh)
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}
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journal = transaction->t_journal;
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JBUFFER_TRACE(jh, "removing from transaction");
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__buffer_unlink(jh);
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jh->b_cp_transaction = NULL;
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journal_put_journal_head(jh);
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if (transaction->t_checkpoint_list != NULL ||
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transaction->t_checkpoint_io_list != NULL)
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goto out;
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JBUFFER_TRACE(jh, "transaction has no more buffers");
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/*
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* There is one special case to worry about: if we have just pulled the
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@ -672,10 +676,8 @@ int __journal_remove_checkpoint(struct journal_head *jh)
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* The locking here around t_state is a bit sleazy.
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* See the comment at the end of journal_commit_transaction().
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*/
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if (transaction->t_state != T_FINISHED) {
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JBUFFER_TRACE(jh, "belongs to running/committing transaction");
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if (transaction->t_state != T_FINISHED)
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goto out;
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}
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/* OK, that was the last buffer for the transaction: we can now
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safely remove this transaction from the log */
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@ -687,7 +689,6 @@ int __journal_remove_checkpoint(struct journal_head *jh)
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wake_up(&journal->j_wait_logspace);
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ret = 1;
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out:
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JBUFFER_TRACE(jh, "exit");
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return ret;
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}
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@ -706,6 +707,8 @@ void __journal_insert_checkpoint(struct journal_head *jh,
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J_ASSERT_JH(jh, buffer_dirty(jh2bh(jh)) || buffer_jbddirty(jh2bh(jh)));
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J_ASSERT_JH(jh, jh->b_cp_transaction == NULL);
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/* Get reference for checkpointing transaction */
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journal_grab_journal_head(jh2bh(jh));
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jh->b_cp_transaction = transaction;
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if (!transaction->t_checkpoint_list) {
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@ -258,10 +258,6 @@ write_out_data:
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jbd_unlock_bh_state(bh);
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if (locked)
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unlock_buffer(bh);
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journal_remove_journal_head(bh);
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/* One for our safety reference, other for
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* journal_remove_journal_head() */
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put_bh(bh);
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release_data_buffer(bh);
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}
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@ -455,14 +451,9 @@ void journal_commit_transaction(journal_t *journal)
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}
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if (buffer_jbd(bh) && bh2jh(bh) == jh &&
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jh->b_transaction == commit_transaction &&
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jh->b_jlist == BJ_Locked) {
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jh->b_jlist == BJ_Locked)
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__journal_unfile_buffer(jh);
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jbd_unlock_bh_state(bh);
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journal_remove_journal_head(bh);
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put_bh(bh);
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} else {
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jbd_unlock_bh_state(bh);
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}
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jbd_unlock_bh_state(bh);
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release_data_buffer(bh);
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cond_resched_lock(&journal->j_list_lock);
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}
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@ -807,10 +798,16 @@ restart_loop:
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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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int try_to_free = 0;
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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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/*
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* Get a reference so that bh cannot be freed before we are
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* done with it.
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*/
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get_bh(bh);
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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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jh->b_transaction == journal->j_running_transaction);
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@ -868,28 +865,27 @@ restart_loop:
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__journal_insert_checkpoint(jh, commit_transaction);
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if (is_journal_aborted(journal))
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clear_buffer_jbddirty(bh);
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JBUFFER_TRACE(jh, "refile for checkpoint writeback");
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__journal_refile_buffer(jh);
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jbd_unlock_bh_state(bh);
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} else {
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J_ASSERT_BH(bh, !buffer_dirty(bh));
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/* The buffer on BJ_Forget list and not jbddirty means
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/*
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* The buffer on BJ_Forget list and not jbddirty means
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* it has been freed by this transaction and hence it
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* could not have been reallocated until this
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* transaction has committed. *BUT* it could be
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* reallocated once we have written all the data to
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* disk and before we process the buffer on BJ_Forget
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* list. */
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JBUFFER_TRACE(jh, "refile or unfile freed buffer");
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__journal_refile_buffer(jh);
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if (!jh->b_transaction) {
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jbd_unlock_bh_state(bh);
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/* needs a brelse */
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journal_remove_journal_head(bh);
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release_buffer_page(bh);
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} else
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jbd_unlock_bh_state(bh);
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* list.
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*/
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if (!jh->b_next_transaction)
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try_to_free = 1;
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}
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JBUFFER_TRACE(jh, "refile or unfile freed buffer");
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__journal_refile_buffer(jh);
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jbd_unlock_bh_state(bh);
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if (try_to_free)
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release_buffer_page(bh);
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else
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__brelse(bh);
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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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@ -1803,10 +1803,9 @@ static void journal_free_journal_head(struct journal_head *jh)
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* When a buffer has its BH_JBD bit set it is immune from being released by
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* core kernel code, mainly via ->b_count.
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*
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* A journal_head may be detached from its buffer_head when the journal_head's
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* b_transaction, b_cp_transaction and b_next_transaction pointers are NULL.
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* Various places in JBD call journal_remove_journal_head() to indicate that the
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* journal_head can be dropped if needed.
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* A journal_head is detached from its buffer_head when the journal_head's
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* b_jcount reaches zero. Running transaction (b_transaction) and checkpoint
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* transaction (b_cp_transaction) hold their references to b_jcount.
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*
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* Various places in the kernel want to attach a journal_head to a buffer_head
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* _before_ attaching the journal_head to a transaction. To protect the
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@ -1819,17 +1818,16 @@ static void journal_free_journal_head(struct journal_head *jh)
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* (Attach a journal_head if needed. Increments b_jcount)
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* struct journal_head *jh = journal_add_journal_head(bh);
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* ...
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* jh->b_transaction = xxx;
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* journal_put_journal_head(jh);
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*
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* Now, the journal_head's b_jcount is zero, but it is safe from being released
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* because it has a non-zero b_transaction.
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* (Get another reference for transaction)
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* journal_grab_journal_head(bh);
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* jh->b_transaction = xxx;
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* (Put original reference)
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* journal_put_journal_head(jh);
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*/
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/*
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* Give a buffer_head a journal_head.
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*
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* Doesn't need the journal lock.
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* May sleep.
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*/
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struct journal_head *journal_add_journal_head(struct buffer_head *bh)
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@ -1893,61 +1891,29 @@ static void __journal_remove_journal_head(struct buffer_head *bh)
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struct journal_head *jh = bh2jh(bh);
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J_ASSERT_JH(jh, jh->b_jcount >= 0);
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get_bh(bh);
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if (jh->b_jcount == 0) {
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if (jh->b_transaction == NULL &&
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jh->b_next_transaction == NULL &&
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jh->b_cp_transaction == NULL) {
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J_ASSERT_JH(jh, jh->b_jlist == BJ_None);
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J_ASSERT_BH(bh, buffer_jbd(bh));
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J_ASSERT_BH(bh, jh2bh(jh) == bh);
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BUFFER_TRACE(bh, "remove journal_head");
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if (jh->b_frozen_data) {
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printk(KERN_WARNING "%s: freeing "
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"b_frozen_data\n",
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__func__);
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jbd_free(jh->b_frozen_data, bh->b_size);
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}
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if (jh->b_committed_data) {
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printk(KERN_WARNING "%s: freeing "
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"b_committed_data\n",
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__func__);
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jbd_free(jh->b_committed_data, bh->b_size);
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}
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bh->b_private = NULL;
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jh->b_bh = NULL; /* debug, really */
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clear_buffer_jbd(bh);
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__brelse(bh);
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journal_free_journal_head(jh);
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} else {
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BUFFER_TRACE(bh, "journal_head was locked");
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}
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J_ASSERT_JH(jh, jh->b_transaction == NULL);
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J_ASSERT_JH(jh, jh->b_next_transaction == NULL);
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J_ASSERT_JH(jh, jh->b_cp_transaction == NULL);
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J_ASSERT_JH(jh, jh->b_jlist == BJ_None);
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J_ASSERT_BH(bh, buffer_jbd(bh));
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J_ASSERT_BH(bh, jh2bh(jh) == bh);
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BUFFER_TRACE(bh, "remove journal_head");
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if (jh->b_frozen_data) {
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printk(KERN_WARNING "%s: freeing b_frozen_data\n", __func__);
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jbd_free(jh->b_frozen_data, bh->b_size);
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}
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if (jh->b_committed_data) {
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printk(KERN_WARNING "%s: freeing b_committed_data\n", __func__);
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jbd_free(jh->b_committed_data, bh->b_size);
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}
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bh->b_private = NULL;
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jh->b_bh = NULL; /* debug, really */
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clear_buffer_jbd(bh);
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journal_free_journal_head(jh);
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}
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/*
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* journal_remove_journal_head(): if the buffer isn't attached to a transaction
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* and has a zero b_jcount then remove and release its journal_head. If we did
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* see that the buffer is not used by any transaction we also "logically"
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* decrement ->b_count.
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*
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* We in fact take an additional increment on ->b_count as a convenience,
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* because the caller usually wants to do additional things with the bh
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* after calling here.
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* The caller of journal_remove_journal_head() *must* run __brelse(bh) at some
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* time. Once the caller has run __brelse(), the buffer is eligible for
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* reaping by try_to_free_buffers().
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*/
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void journal_remove_journal_head(struct buffer_head *bh)
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{
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jbd_lock_bh_journal_head(bh);
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__journal_remove_journal_head(bh);
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jbd_unlock_bh_journal_head(bh);
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}
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/*
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* Drop a reference on the passed journal_head. If it fell to zero then try to
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* Drop a reference on the passed journal_head. If it fell to zero then
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* release the journal_head from the buffer_head.
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*/
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void journal_put_journal_head(struct journal_head *jh)
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@ -1957,11 +1923,12 @@ void journal_put_journal_head(struct journal_head *jh)
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jbd_lock_bh_journal_head(bh);
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J_ASSERT_JH(jh, jh->b_jcount > 0);
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--jh->b_jcount;
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if (!jh->b_jcount && !jh->b_transaction) {
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if (!jh->b_jcount) {
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__journal_remove_journal_head(bh);
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jbd_unlock_bh_journal_head(bh);
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__brelse(bh);
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}
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jbd_unlock_bh_journal_head(bh);
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} else
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jbd_unlock_bh_journal_head(bh);
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}
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/*
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@ -696,7 +696,6 @@ repeat:
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if (!jh->b_transaction) {
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JBUFFER_TRACE(jh, "no transaction");
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J_ASSERT_JH(jh, !jh->b_next_transaction);
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jh->b_transaction = transaction;
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JBUFFER_TRACE(jh, "file as BJ_Reserved");
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spin_lock(&journal->j_list_lock);
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__journal_file_buffer(jh, transaction, BJ_Reserved);
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@ -818,7 +817,6 @@ int journal_get_create_access(handle_t *handle, struct buffer_head *bh)
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* committed and so it's safe to clear the dirty bit.
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*/
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clear_buffer_dirty(jh2bh(jh));
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jh->b_transaction = transaction;
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/* first access by this transaction */
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jh->b_modified = 0;
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@ -1069,8 +1067,9 @@ int journal_dirty_data(handle_t *handle, struct buffer_head *bh)
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ret = -EIO;
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goto no_journal;
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}
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if (jh->b_transaction != NULL) {
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/* We might have slept so buffer could be refiled now */
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if (jh->b_transaction != NULL &&
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jh->b_transaction != handle->h_transaction) {
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JBUFFER_TRACE(jh, "unfile from commit");
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__journal_temp_unlink_buffer(jh);
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/* It still points to the committing
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@ -1091,8 +1090,6 @@ int journal_dirty_data(handle_t *handle, struct buffer_head *bh)
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if (jh->b_jlist != BJ_SyncData && jh->b_jlist != BJ_Locked) {
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JBUFFER_TRACE(jh, "not on correct data list: unfile");
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J_ASSERT_JH(jh, jh->b_jlist != BJ_Shadow);
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__journal_temp_unlink_buffer(jh);
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jh->b_transaction = handle->h_transaction;
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JBUFFER_TRACE(jh, "file as data");
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__journal_file_buffer(jh, handle->h_transaction,
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BJ_SyncData);
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@ -1300,8 +1297,6 @@ int journal_forget (handle_t *handle, struct buffer_head *bh)
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__journal_file_buffer(jh, transaction, BJ_Forget);
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} else {
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__journal_unfile_buffer(jh);
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journal_remove_journal_head(bh);
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__brelse(bh);
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if (!buffer_jbd(bh)) {
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spin_unlock(&journal->j_list_lock);
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jbd_unlock_bh_state(bh);
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@ -1622,19 +1617,32 @@ static void __journal_temp_unlink_buffer(struct journal_head *jh)
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mark_buffer_dirty(bh); /* Expose it to the VM */
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}
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/*
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* Remove buffer from all transactions.
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*
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* Called with bh_state lock and j_list_lock
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*
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* jh and bh may be already freed when this function returns.
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*/
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void __journal_unfile_buffer(struct journal_head *jh)
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{
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__journal_temp_unlink_buffer(jh);
|
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jh->b_transaction = NULL;
|
||||
journal_put_journal_head(jh);
|
||||
}
|
||||
|
||||
void journal_unfile_buffer(journal_t *journal, struct journal_head *jh)
|
||||
{
|
||||
jbd_lock_bh_state(jh2bh(jh));
|
||||
struct buffer_head *bh = jh2bh(jh);
|
||||
|
||||
/* Get reference so that buffer cannot be freed before we unlock it */
|
||||
get_bh(bh);
|
||||
jbd_lock_bh_state(bh);
|
||||
spin_lock(&journal->j_list_lock);
|
||||
__journal_unfile_buffer(jh);
|
||||
spin_unlock(&journal->j_list_lock);
|
||||
jbd_unlock_bh_state(jh2bh(jh));
|
||||
jbd_unlock_bh_state(bh);
|
||||
__brelse(bh);
|
||||
}
|
||||
|
||||
/*
|
||||
@ -1661,16 +1669,12 @@ __journal_try_to_free_buffer(journal_t *journal, struct buffer_head *bh)
|
||||
/* A written-back ordered data buffer */
|
||||
JBUFFER_TRACE(jh, "release data");
|
||||
__journal_unfile_buffer(jh);
|
||||
journal_remove_journal_head(bh);
|
||||
__brelse(bh);
|
||||
}
|
||||
} else if (jh->b_cp_transaction != NULL && jh->b_transaction == NULL) {
|
||||
/* written-back checkpointed metadata buffer */
|
||||
if (jh->b_jlist == BJ_None) {
|
||||
JBUFFER_TRACE(jh, "remove from checkpoint list");
|
||||
__journal_remove_checkpoint(jh);
|
||||
journal_remove_journal_head(bh);
|
||||
__brelse(bh);
|
||||
}
|
||||
}
|
||||
spin_unlock(&journal->j_list_lock);
|
||||
@ -1733,7 +1737,7 @@ int journal_try_to_free_buffers(journal_t *journal,
|
||||
/*
|
||||
* We take our own ref against the journal_head here to avoid
|
||||
* having to add tons of locking around each instance of
|
||||
* journal_remove_journal_head() and journal_put_journal_head().
|
||||
* journal_put_journal_head().
|
||||
*/
|
||||
jh = journal_grab_journal_head(bh);
|
||||
if (!jh)
|
||||
@ -1770,10 +1774,9 @@ static int __dispose_buffer(struct journal_head *jh, transaction_t *transaction)
|
||||
int may_free = 1;
|
||||
struct buffer_head *bh = jh2bh(jh);
|
||||
|
||||
__journal_unfile_buffer(jh);
|
||||
|
||||
if (jh->b_cp_transaction) {
|
||||
JBUFFER_TRACE(jh, "on running+cp transaction");
|
||||
__journal_temp_unlink_buffer(jh);
|
||||
/*
|
||||
* We don't want to write the buffer anymore, clear the
|
||||
* bit so that we don't confuse checks in
|
||||
@ -1784,8 +1787,7 @@ static int __dispose_buffer(struct journal_head *jh, transaction_t *transaction)
|
||||
may_free = 0;
|
||||
} else {
|
||||
JBUFFER_TRACE(jh, "on running transaction");
|
||||
journal_remove_journal_head(bh);
|
||||
__brelse(bh);
|
||||
__journal_unfile_buffer(jh);
|
||||
}
|
||||
return may_free;
|
||||
}
|
||||
@ -2070,6 +2072,8 @@ void __journal_file_buffer(struct journal_head *jh,
|
||||
|
||||
if (jh->b_transaction)
|
||||
__journal_temp_unlink_buffer(jh);
|
||||
else
|
||||
journal_grab_journal_head(bh);
|
||||
jh->b_transaction = transaction;
|
||||
|
||||
switch (jlist) {
|
||||
@ -2127,9 +2131,10 @@ void journal_file_buffer(struct journal_head *jh,
|
||||
* already started to be used by a subsequent transaction, refile the
|
||||
* buffer on that transaction's metadata list.
|
||||
*
|
||||
* Called under journal->j_list_lock
|
||||
*
|
||||
* Called under j_list_lock
|
||||
* Called under jbd_lock_bh_state(jh2bh(jh))
|
||||
*
|
||||
* jh and bh may be already free when this function returns
|
||||
*/
|
||||
void __journal_refile_buffer(struct journal_head *jh)
|
||||
{
|
||||
@ -2153,6 +2158,11 @@ void __journal_refile_buffer(struct journal_head *jh)
|
||||
|
||||
was_dirty = test_clear_buffer_jbddirty(bh);
|
||||
__journal_temp_unlink_buffer(jh);
|
||||
/*
|
||||
* We set b_transaction here because b_next_transaction will inherit
|
||||
* our jh reference and thus __journal_file_buffer() must not take a
|
||||
* new one.
|
||||
*/
|
||||
jh->b_transaction = jh->b_next_transaction;
|
||||
jh->b_next_transaction = NULL;
|
||||
if (buffer_freed(bh))
|
||||
@ -2169,30 +2179,21 @@ void __journal_refile_buffer(struct journal_head *jh)
|
||||
}
|
||||
|
||||
/*
|
||||
* For the unlocked version of this call, also make sure that any
|
||||
* hanging journal_head is cleaned up if necessary.
|
||||
* __journal_refile_buffer() with necessary locking added. We take our bh
|
||||
* reference so that we can safely unlock bh.
|
||||
*
|
||||
* __journal_refile_buffer is usually called as part of a single locked
|
||||
* operation on a buffer_head, in which the caller is probably going to
|
||||
* be hooking the journal_head onto other lists. In that case it is up
|
||||
* to the caller to remove the journal_head if necessary. For the
|
||||
* unlocked journal_refile_buffer call, the caller isn't going to be
|
||||
* doing anything else to the buffer so we need to do the cleanup
|
||||
* ourselves to avoid a jh leak.
|
||||
*
|
||||
* *** The journal_head may be freed by this call! ***
|
||||
* The jh and bh may be freed by this call.
|
||||
*/
|
||||
void journal_refile_buffer(journal_t *journal, struct journal_head *jh)
|
||||
{
|
||||
struct buffer_head *bh = jh2bh(jh);
|
||||
|
||||
/* Get reference so that buffer cannot be freed before we unlock it */
|
||||
get_bh(bh);
|
||||
jbd_lock_bh_state(bh);
|
||||
spin_lock(&journal->j_list_lock);
|
||||
|
||||
__journal_refile_buffer(jh);
|
||||
jbd_unlock_bh_state(bh);
|
||||
journal_remove_journal_head(bh);
|
||||
|
||||
spin_unlock(&journal->j_list_lock);
|
||||
__brelse(bh);
|
||||
}
|
||||
|
||||
@ -940,7 +940,6 @@ extern int journal_force_commit(journal_t *);
|
||||
*/
|
||||
struct journal_head *journal_add_journal_head(struct buffer_head *bh);
|
||||
struct journal_head *journal_grab_journal_head(struct buffer_head *bh);
|
||||
void journal_remove_journal_head(struct buffer_head *bh);
|
||||
void journal_put_journal_head(struct journal_head *jh);
|
||||
|
||||
/*
|
||||
|
||||
Loading…
Reference in New Issue
Block a user