If no_nrwrite_update is set we don't update nr_to_write in
write_cache_pages. Similarly if no_index_update is we don't
update address space writeback_index. These changes enable a
file system to skip these updates in write_cache_pages and do
them in the writepages() callback. This patch will be followed
by an ext4 patch that make use of these new flags.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
CC: linux-fsdevel@xxxxxxxxxxxxxxx
---
include/linux/writeback.h | 4 ++++
mm/page-writeback.c | 9 +++++++--
2 files changed, 11 insertions(+), 2 deletions(-)
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index bd91987..b04287e 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -63,6 +63,10 @@ struct writeback_control {
unsigned for_writepages:1; /* This is a writepages() call */
unsigned range_cyclic:1; /* range_start is cyclic */
unsigned more_io:1; /* more io to be dispatched */
+
+ /* write_cache_pages() control */
+ unsigned no_nrwrite_update:1; /* don't update nr_to_write */
+ unsigned no_index_update:1; /* don't update writeback_index */
};
/*
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 718efa6..4f359f4 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -876,6 +876,7 @@ int write_cache_pages(struct address_space *mapping,
pgoff_t end; /* Inclusive */
int scanned = 0;
int range_whole = 0;
+ long nr_to_write = wbc->nr_to_write;
if (wbc->nonblocking && bdi_write_congested(bdi)) {
wbc->encountered_congestion = 1;
@@ -939,7 +940,7 @@ int write_cache_pages(struct address_space *mapping,
unlock_page(page);
ret = 0;
}
- if (ret || (--(wbc->nr_to_write) <= 0))
+ if (ret || (--nr_to_write <= 0))
done = 1;
if (wbc->nonblocking && bdi_write_congested(bdi)) {
wbc->encountered_congestion = 1;
@@ -958,8 +959,12 @@ int write_cache_pages(struct address_space *mapping,
index = 0;
goto retry;
}
- if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
+ if (!wbc->no_index_update &&
+ (wbc->range_cyclic || (range_whole && nr_to_write > 0))) {
mapping->writeback_index = index;
+ }
+ if (!wbc->no_nrwrite_update)
+ wbc->nr_to_write = nr_to_write;
return ret;
}
--
1.6.0.2.526.g5c283
--
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