* [PATCH 1/2] block: simplify bio_check_pages_dirty
2018-07-24 12:04 two small bio cleanups Christoph Hellwig
@ 2018-07-24 12:04 ` Christoph Hellwig
2018-07-24 12:04 ` [PATCH 2/2] block: bio_set_pages_dirty can't see NULL bv_page in a valid bio_vec Christoph Hellwig
2018-07-24 20:41 ` two small bio cleanups Jens Axboe
2 siblings, 0 replies; 4+ messages in thread
From: Christoph Hellwig @ 2018-07-24 12:04 UTC (permalink / raw)
To: axboe; +Cc: linux-block
bio_check_pages_dirty currently inviolates the invariant that bv_page of
a bio_vec inside bi_vcnt shouldn't be zero, and that is going to become
really annoying with multpath biovecs. Fortunately there isn't any
all that good reason for it - once we decide to defer freeing the bio
to a workqueue holding onto a few additional pages isn't really an
issue anymore. So just check if there is a clean page that needs
dirtying in the first path, and do a second pass to free them if there
was none, while the cache is still hot.
Also use the chance to micro-optimize bio_dirty_fn a bit by not saving
irq state - we know we are called from a workqueue.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
---
block/bio.c | 56 ++++++++++++++++++++---------------------------------
1 file changed, 21 insertions(+), 35 deletions(-)
diff --git a/block/bio.c b/block/bio.c
index 8ecc95615941..504b42278099 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1649,19 +1649,15 @@ static void bio_release_pages(struct bio *bio)
struct bio_vec *bvec;
int i;
- bio_for_each_segment_all(bvec, bio, i) {
- struct page *page = bvec->bv_page;
-
- if (page)
- put_page(page);
- }
+ bio_for_each_segment_all(bvec, bio, i)
+ put_page(bvec->bv_page);
}
/*
* bio_check_pages_dirty() will check that all the BIO's pages are still dirty.
* If they are, then fine. If, however, some pages are clean then they must
* have been written out during the direct-IO read. So we take another ref on
- * the BIO and the offending pages and re-dirty the pages in process context.
+ * the BIO and re-dirty the pages in process context.
*
* It is expected that bio_check_pages_dirty() will wholly own the BIO from
* here on. It will run one put_page() against each page and will run one
@@ -1679,52 +1675,42 @@ static struct bio *bio_dirty_list;
*/
static void bio_dirty_fn(struct work_struct *work)
{
- unsigned long flags;
- struct bio *bio;
+ struct bio *bio, *next;
- spin_lock_irqsave(&bio_dirty_lock, flags);
- bio = bio_dirty_list;
+ spin_lock_irq(&bio_dirty_lock);
+ next = bio_dirty_list;
bio_dirty_list = NULL;
- spin_unlock_irqrestore(&bio_dirty_lock, flags);
+ spin_unlock_irq(&bio_dirty_lock);
- while (bio) {
- struct bio *next = bio->bi_private;
+ while ((bio = next) != NULL) {
+ next = bio->bi_private;
bio_set_pages_dirty(bio);
bio_release_pages(bio);
bio_put(bio);
- bio = next;
}
}
void bio_check_pages_dirty(struct bio *bio)
{
struct bio_vec *bvec;
- int nr_clean_pages = 0;
+ unsigned long flags;
int i;
bio_for_each_segment_all(bvec, bio, i) {
- struct page *page = bvec->bv_page;
-
- if (PageDirty(page) || PageCompound(page)) {
- put_page(page);
- bvec->bv_page = NULL;
- } else {
- nr_clean_pages++;
- }
+ if (!PageDirty(bvec->bv_page) && !PageCompound(bvec->bv_page))
+ goto defer;
}
- if (nr_clean_pages) {
- unsigned long flags;
-
- spin_lock_irqsave(&bio_dirty_lock, flags);
- bio->bi_private = bio_dirty_list;
- bio_dirty_list = bio;
- spin_unlock_irqrestore(&bio_dirty_lock, flags);
- schedule_work(&bio_dirty_work);
- } else {
- bio_put(bio);
- }
+ bio_release_pages(bio);
+ bio_put(bio);
+ return;
+defer:
+ spin_lock_irqsave(&bio_dirty_lock, flags);
+ bio->bi_private = bio_dirty_list;
+ bio_dirty_list = bio;
+ spin_unlock_irqrestore(&bio_dirty_lock, flags);
+ schedule_work(&bio_dirty_work);
}
EXPORT_SYMBOL_GPL(bio_check_pages_dirty);
--
2.18.0
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