writeback: move last_active to bdi

Currently bdi threads use local variable 'last_active' which stores last time
when the bdi thread did some useful work. Move this local variable to 'struct
bdi_writeback'. This is just a preparation for the further patches which will
make the forker thread decide when bdi threads should be killed.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

2 files changed, 10 insertions, 9 deletions

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 57fbfd0ebc52..9f5cab75c157 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -800,12 +800,12 @@ int bdi_writeback_thread(void *data)
 {
         struct bdi_writeback *wb = data;
         struct backing_dev_info *bdi = wb->bdi;
-        unsigned long last_active = jiffies;
         unsigned long wait_jiffies = -1UL;
         long pages_written;
 
         current->flags |= PF_FLUSHER | PF_SWAPWRITE;
         set_freezable();
+        wb->last_active = jiffies;
 
         /*
          * Our parent may run at a different priority, just set us to normal
@@ -827,7 +827,7 @@ int bdi_writeback_thread(void *data)
                 trace_writeback_pages_written(pages_written);
 
                 if (pages_written)
-                        last_active = jiffies;
+                        wb->last_active = jiffies;
                 else if (wait_jiffies != -1UL) {
                         unsigned long max_idle;
 
@@ -837,7 +837,7 @@ int bdi_writeback_thread(void *data)
                          * recreated automatically.
                          */
                         max_idle = max(5UL * 60 * HZ, wait_jiffies);
-                        if (time_after(jiffies, max_idle + last_active))
+                        if (time_after(jiffies, max_idle + wb->last_active))
                                 break;
                 }
 
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 95ecb2bebca8..71b6223e0a77 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -45,15 +45,16 @@ enum bdi_stat_item {
 #define BDI_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))
 
 struct bdi_writeback {
-        struct backing_dev_info *bdi;           /* our parent bdi */
+        struct backing_dev_info *bdi;   /* our parent bdi */
         unsigned int nr;
 
-        unsigned long last_old_flush;           /* last old data flush */
+        unsigned long last_old_flush;   /* last old data flush */
+        unsigned long last_active;      /* last time bdi thread was active */
 
-        struct task_struct      *task;          /* writeback thread */
-        struct list_head        b_dirty;        /* dirty inodes */
-        struct list_head        b_io;           /* parked for writeback */
-        struct list_head        b_more_io;      /* parked for more writeback */
+        struct task_struct *task;       /* writeback thread */
+        struct list_head b_dirty;       /* dirty inodes */
+        struct list_head b_io;          /* parked for writeback */
+        struct list_head b_more_io;     /* parked for more writeback */
 };
 
 struct backing_dev_info {