md: prepare for managing resync I/O pages in clean way

Now resync I/O use bio's bec table to manage pages,
this way is very hacky, and may not work any more
once multipage bvec is introduced.

So introduce helpers and new data structure for
managing resync I/O pages more cleanly.

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Shaohua Li <shli@fb.com>

diff --git a/drivers/md/md.h b/drivers/md/md.h
index 31d2d70849b62ba4312964da160070a6ad4f9ab8..0418b29945e7a88ab414c96ff2f623a9f891bcaa 100644 (file)
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -723,4 +723,54 @@ static inline void mddev_check_writesame(struct mddev *mddev, struct bio *bio)
 #define RESYNC_BLOCK_SIZE (64*1024)
 #define RESYNC_PAGES ((RESYNC_BLOCK_SIZE + PAGE_SIZE-1) / PAGE_SIZE)
 
+/* for managing resync I/O pages */
+struct resync_pages {
+       unsigned        idx;    /* for get/put page from the pool */
+       void            *raid_bio;
+       struct page     *pages[RESYNC_PAGES];
+};
+
+static inline int resync_alloc_pages(struct resync_pages *rp,
+                                    gfp_t gfp_flags)
+{
+       int i;
+
+       for (i = 0; i < RESYNC_PAGES; i++) {
+               rp->pages[i] = alloc_page(gfp_flags);
+               if (!rp->pages[i])
+                       goto out_free;
+       }
+
+       return 0;
+
+out_free:
+       while (--i >= 0)
+               put_page(rp->pages[i]);
+       return -ENOMEM;
+}
+
+static inline void resync_free_pages(struct resync_pages *rp)
+{
+       int i;
+
+       for (i = 0; i < RESYNC_PAGES; i++)
+               put_page(rp->pages[i]);
+}
+
+static inline void resync_get_all_pages(struct resync_pages *rp)
+{
+       int i;
+
+       for (i = 0; i < RESYNC_PAGES; i++)
+               get_page(rp->pages[i]);
+}
+
+static inline struct page *resync_fetch_page(struct resync_pages *rp,
+                                            unsigned idx)
+{
+       if (WARN_ON_ONCE(idx >= RESYNC_PAGES))
+               return NULL;
+       return rp->pages[idx];
+}
+
 #endif /* _MD_MD_H */