If no_nrwrite_index_update is set we don't update nr_to_write
and address space writeback_index in write_cache_pages.
This change 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 | 9 +++++++++
mm/page-writeback.c | 10 +++++++---
2 files changed, 16 insertions(+), 3 deletions(-)
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index bd91987..4de3941 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -63,6 +63,15 @@ 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 won't update wbc->nr_to_write and
+ * mapping->writeback_index if no_nrwrite_index_update
+ * is set. write_cache_pages may write more than we
+ * requested and we want to make sure nr_to_write and
+ * writeback_index are updated in a consistent manner
+ * so we use a single control to update them
+ */
+ unsigned no_nrwrite_index_update:1;
};
/*
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 718efa6..b6d66d3 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 +959,11 @@ int write_cache_pages(struct address_space *mapping,
index = 0;
goto retry;
}
- if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
- mapping->writeback_index = index;
+ if (!wbc->no_nrwrite_index_update) {
+ if (wbc->range_cyclic || (range_whole && nr_to_write > 0))
+ mapping->writeback_index = index;
+ wbc->nr_to_write = nr_to_write;
+ }
return ret;
}
--
1.6.0.2.526.g5c283
--
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