f2fs: reclaim prefree segments periodically

Previously, f2fs postpones reclaiming prefree segments into free segments
as much as possible.
However, if user writes and deletes a bunch of data without any sync or fsync
calls, some flash storages can suffer from garbage collections.

So, this patch adds the reclaiming codes to f2fs_write_node_pages and background
GC thread.

If there are a lot of prefree segments, let's do checkpoint so that f2fs
submits discard commands for the prefree regions to the flash storage.

Signed-off-by: Changman Lee <cm224.lee@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index e8f3fd345ca3..6dff777cd94a 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -299,6 +299,9 @@ struct f2fs_sm_info {
         unsigned int main_segments;     /* # of segments in main area */
         unsigned int reserved_segments; /* # of reserved segments */
         unsigned int ovp_segments;      /* # of overprovision segments */
+
+        /* a threshold to reclaim prefree segments */
+        unsigned int rec_prefree_segments;
 };
 
 /*