block: implement bio_associate_current()

[linux-2.6-block.git] / fs / bio.c

diff --git a/fs/bio.c b/fs/bio.c
index b1fe82cf88cfe0864a2d9603b713f8caacecde4e..142214b80039f5d216f6b5c55329056e62c6bade 100644 (file)
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -19,12 +19,14 @@
 #include <linux/swap.h>
 #include <linux/bio.h>
 #include <linux/blkdev.h>
+#include <linux/iocontext.h>
 #include <linux/slab.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/mempool.h>
 #include <linux/workqueue.h>
+#include <linux/cgroup.h>
 #include <scsi/sg.h>           /* for struct sg_iovec */
 
 #include <trace/events/block.h>
@@ -418,6 +420,7 @@ void bio_put(struct bio *bio)
         * last put frees it
         */
        if (atomic_dec_and_test(&bio->bi_cnt)) {
+               bio_disassociate_task(bio);
                bio->bi_next = NULL;
                bio->bi_destructor(bio);
        }
@@ -505,13 +508,9 @@ EXPORT_SYMBOL(bio_clone);
 int bio_get_nr_vecs(struct block_device *bdev)
 {
        struct request_queue *q = bdev_get_queue(bdev);
-       int nr_pages;
-
-       nr_pages = ((queue_max_sectors(q) << 9) + PAGE_SIZE - 1) >> PAGE_SHIFT;
-       if (nr_pages > queue_max_segments(q))
-               nr_pages = queue_max_segments(q);
-
-       return nr_pages;
+       return min_t(unsigned,
+                    queue_max_segments(q),
+                    queue_max_sectors(q) / (PAGE_SIZE >> 9) + 1);
 }
 EXPORT_SYMBOL(bio_get_nr_vecs);
 
@@ -1645,6 +1644,64 @@ bad:
 }
 EXPORT_SYMBOL(bioset_create);
 
+#ifdef CONFIG_BLK_CGROUP
+/**
+ * bio_associate_current - associate a bio with %current
+ * @bio: target bio
+ *
+ * Associate @bio with %current if it hasn't been associated yet.  Block
+ * layer will treat @bio as if it were issued by %current no matter which
+ * task actually issues it.
+ *
+ * This function takes an extra reference of @task's io_context and blkcg
+ * which will be put when @bio is released.  The caller must own @bio,
+ * ensure %current->io_context exists, and is responsible for synchronizing
+ * calls to this function.
+ */
+int bio_associate_current(struct bio *bio)
+{
+       struct io_context *ioc;
+       struct cgroup_subsys_state *css;
+
+       if (bio->bi_ioc)
+               return -EBUSY;
+
+       ioc = current->io_context;
+       if (!ioc)
+               return -ENOENT;
+
+       /* acquire active ref on @ioc and associate */
+       get_io_context_active(ioc);
+       bio->bi_ioc = ioc;
+
+       /* associate blkcg if exists */
+       rcu_read_lock();
+       css = task_subsys_state(current, blkio_subsys_id);
+       if (css && css_tryget(css))
+               bio->bi_css = css;
+       rcu_read_unlock();
+
+       return 0;
+}
+
+/**
+ * bio_disassociate_task - undo bio_associate_current()
+ * @bio: target bio
+ */
+void bio_disassociate_task(struct bio *bio)
+{
+       if (bio->bi_ioc) {
+               put_io_context(bio->bi_ioc);
+               bio->bi_ioc = NULL;
+       }
+       if (bio->bi_css) {
+               css_put(bio->bi_css);
+               bio->bi_css = NULL;
+       }
+}
+
+#endif /* CONFIG_BLK_CGROUP */
+
 static void __init biovec_init_slabs(void)
 {
        int i;