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block: simplify bio_check_pages_dirty

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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>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Christoph Hellwig 2018-07-24 14:04:12 +02:00 committed by Jens Axboe
parent 76f17d8ba1
commit 24d5493f20
1 changed files with 21 additions and 35 deletions
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56
block/bio.c
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@ -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);