When past EOF, abort the writeback of the current inode, which will
instruct writeback_single_inode() to redirty_tail() it.
This is the right behavior for
- sync writeback (is already so with range_whole)
we have scanned the inode address space, and don't care any more newly
dirtied pages. So shall update its i_dirtied_when and exclude it from
the todo list.
- periodic writeback
any more newly dirtied pages should be associated with a new expire
time. This also prevents pointless IO for busy overwriters.
- background writeback (irrelevant)
it generally don't care the dirty timestamp.
That should get rid of one inefficient IO pattern of .range_cyclic when
writeback_index wraps, in which the submitted pages may be consisted of
two distant ranges: submit [10000-10100], (wrap), submit [0-100].
The new .stop_on_wrap is a quick hack to show the basic idea. Ideal
would be to just convert the existing .range_cyclic to new behavior.
This should simplify a lot of code.
Since this involves many filesystems. I'd like to ask if any of them
in fact _desire_ the current .range_cyclic semantics to wrap?
Thanks,
Fengguang
---
fs/fs-writeback.c | 1 +
include/linux/writeback.h | 1 +
mm/page-writeback.c | 4 +++-
3 files changed, 5 insertions(+), 1 deletion(-)
--- linux.orig/fs/fs-writeback.c 2009-10-02 16:46:36.000000000 +0800
+++ linux/fs/fs-writeback.c 2009-10-02 17:01:27.000000000 +0800
@@ -810,6 +810,7 @@ static long wb_writeback(struct bdi_writ
.for_kupdate = args->for_kupdate,
.for_background = args->for_background,
.range_cyclic = args->range_cyclic,
+ .stop_on_wrap = 1,
};
unsigned long oldest_jif;
long wrote = 0;
--- linux.orig/include/linux/writeback.h 2009-10-02 16:46:36.000000000 +0800
+++ linux/include/linux/writeback.h 2009-10-02 16:57:13.000000000 +0800
@@ -57,6 +57,7 @@ struct writeback_control {
unsigned for_background:1; /* A background writeback */
unsigned for_reclaim:1; /* Invoked from the page allocator */
unsigned range_cyclic:1; /* range_start is cyclic */
+ unsigned stop_on_wrap:1; /* stop when write index is to wrap */
unsigned more_io:1; /* more io to be dispatched */
/*
* write_cache_pages() won't update wbc->nr_to_write and
--- linux.orig/mm/page-writeback.c 2009-10-02 16:46:36.000000000 +0800
+++ linux/mm/page-writeback.c 2009-10-02 16:57:13.000000000 +0800
@@ -913,7 +913,9 @@ continue_unlock:
break;
}
}
- if (!cycled && !done) {
+ if (wbc->stop_on_wrap)
+ done_index = 0;
+ else if (!cycled && !done) {
/*
* range_cyclic:
* We hit the last page and there is more work to be done: wrap
--
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