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writeback: Add tracing to write_cache_pages

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Add a trace event to the ->writepage loop in write_cache_pages to give
visibility into how the ->writepage call is changing variables within the
writeback control structure. Of most interest is how wbc->nr_to_write changes
from call to call, especially with filesystems that write multiple pages
in ->writepage.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
This commit is contained in:
Dave Chinner 2010-07-07 13:24:08 +10:00 committed by Jens Axboe
parent 028c2dd184
commit 9e094383b6
2 changed files with 2 additions and 0 deletions
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1
include/trace/events/writeback.h
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@ -148,6 +148,7 @@ DEFINE_WBC_EVENT(wbc_writeback_wait);
DEFINE_WBC_EVENT(wbc_balance_dirty_start);
DEFINE_WBC_EVENT(wbc_balance_dirty_written);
DEFINE_WBC_EVENT(wbc_balance_dirty_wait);
DEFINE_WBC_EVENT(wbc_writepage);
#endif /* _TRACE_WRITEBACK_H */

1
mm/page-writeback.c
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@ -933,6 +933,7 @@ continue_unlock:
if (!clear_page_dirty_for_io(page))
goto continue_unlock;
trace_wbc_writepage(wbc, mapping->backing_dev_info);
ret = (*writepage)(page, wbc, data);
if (unlikely(ret)) {
if (ret == AOP_WRITEPAGE_ACTIVATE) {