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authorJoel Becker <joel.becker@oracle.com>2008-09-11 15:35:47 -0700
committerMark Fasheh <mfasheh@suse.com>2009-01-05 08:40:30 -0800
commite06c8227fd94ec181849ba206bf032be31c4295c (patch)
tree67261cd94aa86dc6112d7de74304c2a1af5b64fb /fs/jbd2/journal.c
parent754938c142ae0c28360426c43f965ddc5164b21e (diff)
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jbd2: Add buffer triggers
Filesystems often to do compute intensive operation on some metadata. If this operation is repeated many times, it can be very expensive. It would be much nicer if the operation could be performed once before a buffer goes to disk. This adds triggers to jbd2 buffer heads. Just before writing a metadata buffer to the journal, jbd2 will optionally call a commit trigger associated with the buffer. If the journal is aborted, an abort trigger will be called on any dirty buffers as they are dropped from pending transactions. ocfs2 will use this feature. Initially I tried to come up with a more generic trigger that could be used for non-buffer-related events like transaction completion. It doesn't tie nicely, because the information a buffer trigger needs (specific to a journal_head) isn't the same as what a transaction trigger needs (specific to a tranaction_t or perhaps journal_t). So I implemented a buffer set, with the understanding that journal/transaction wide triggers should be implemented separately. There is only one trigger set allowed per buffer. I can't think of any reason to attach more than one set. Contrast this with a journal or transaction in which multiple places may want to watch the entire transaction separately. The trigger sets are considered static allocation from the jbd2 perspective. ocfs2 will just have one trigger set per block type, setting the same set on every bh of the same type. Signed-off-by: Joel Becker <joel.becker@oracle.com> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: <linux-ext4@vger.kernel.org> Signed-off-by: Mark Fasheh <mfasheh@suse.com>
Diffstat (limited to 'fs/jbd2/journal.c')
-rw-r--r--fs/jbd2/journal.c19
1 files changed, 19 insertions, 0 deletions
diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index e70d657a19f..f6bff9d6f8d 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -50,6 +50,7 @@ EXPORT_SYMBOL(jbd2_journal_unlock_updates);
EXPORT_SYMBOL(jbd2_journal_get_write_access);
EXPORT_SYMBOL(jbd2_journal_get_create_access);
EXPORT_SYMBOL(jbd2_journal_get_undo_access);
+EXPORT_SYMBOL(jbd2_journal_set_triggers);
EXPORT_SYMBOL(jbd2_journal_dirty_metadata);
EXPORT_SYMBOL(jbd2_journal_release_buffer);
EXPORT_SYMBOL(jbd2_journal_forget);
@@ -290,6 +291,7 @@ int jbd2_journal_write_metadata_buffer(transaction_t *transaction,
struct page *new_page;
unsigned int new_offset;
struct buffer_head *bh_in = jh2bh(jh_in);
+ struct jbd2_buffer_trigger_type *triggers;
/*
* The buffer really shouldn't be locked: only the current committing
@@ -314,13 +316,23 @@ repeat:
done_copy_out = 1;
new_page = virt_to_page(jh_in->b_frozen_data);
new_offset = offset_in_page(jh_in->b_frozen_data);
+ triggers = jh_in->b_frozen_triggers;
} else {
new_page = jh2bh(jh_in)->b_page;
new_offset = offset_in_page(jh2bh(jh_in)->b_data);
+ triggers = jh_in->b_triggers;
}
mapped_data = kmap_atomic(new_page, KM_USER0);
/*
+ * Fire any commit trigger. Do this before checking for escaping,
+ * as the trigger may modify the magic offset. If a copy-out
+ * happens afterwards, it will have the correct data in the buffer.
+ */
+ jbd2_buffer_commit_trigger(jh_in, mapped_data + new_offset,
+ triggers);
+
+ /*
* Check for escaping
*/
if (*((__be32 *)(mapped_data + new_offset)) ==
@@ -352,6 +364,13 @@ repeat:
new_page = virt_to_page(tmp);
new_offset = offset_in_page(tmp);
done_copy_out = 1;
+
+ /*
+ * This isn't strictly necessary, as we're using frozen
+ * data for the escaping, but it keeps consistency with
+ * b_frozen_data usage.
+ */
+ jh_in->b_frozen_triggers = jh_in->b_triggers;
}
/*