| Message ID | 7d99fa-9c13-ab2a-acde-1f8bbc63bf3@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | brd discard patches | expand |
> Index: linux-2.6/drivers/block/brd.c > =================================================================== > --- linux-2.6.orig/drivers/block/brd.c > +++ linux-2.6/drivers/block/brd.c > @@ -150,23 +150,27 @@ static void copy_to_brd(struct brd_devic > size_t copy; > > copy = min_t(size_t, n, PAGE_SIZE - offset); > + rcu_read_lock(); > page = brd_lookup_page(brd, sector); xa_load() inside brd_lookup_page() also calls rcu read lock. Instead of nesting rcu locks, could we modify the brd_lookup_page to use: diff --git a/drivers/block/brd.c b/drivers/block/brd.c index 970bd6ff38c4..acc37bfdd181 100644 --- a/drivers/block/brd.c +++ b/drivers/block/brd.c @@ -55,7 +55,9 @@ static struct page *brd_lookup_page(struct brd_device *brd, sector_t sector) struct page *page; idx = sector >> PAGE_SECTORS_SHIFT; /* sector to page index */ - page = xa_load(&brd->brd_pages, idx); + + XA_STATE(xas, &brd->brd_pages, idx); + page = xas_load(&xas); BUG_ON(page && page->index != idx); > BUG_ON(!page); > > dst = kmap_atomic(page); > memcpy(dst + offset, src, copy); > kunmap_atomic(dst);
Index: linux-2.6/drivers/block/brd.c =================================================================== --- linux-2.6.orig/drivers/block/brd.c +++ linux-2.6/drivers/block/brd.c @@ -150,23 +150,27 @@ static void copy_to_brd(struct brd_devic size_t copy; copy = min_t(size_t, n, PAGE_SIZE - offset); + rcu_read_lock(); page = brd_lookup_page(brd, sector); BUG_ON(!page); dst = kmap_atomic(page); memcpy(dst + offset, src, copy); kunmap_atomic(dst); + rcu_read_unlock(); if (copy < n) { src += copy; sector += copy >> SECTOR_SHIFT; copy = n - copy; + rcu_read_lock(); page = brd_lookup_page(brd, sector); BUG_ON(!page); dst = kmap_atomic(page); memcpy(dst, src, copy); kunmap_atomic(dst); + rcu_read_unlock(); } } @@ -182,6 +186,7 @@ static void copy_from_brd(void *dst, str size_t copy; copy = min_t(size_t, n, PAGE_SIZE - offset); + rcu_read_lock(); page = brd_lookup_page(brd, sector); if (page) { src = kmap_atomic(page); @@ -189,11 +194,13 @@ static void copy_from_brd(void *dst, str kunmap_atomic(src); } else memset(dst, 0, copy); + rcu_read_unlock(); if (copy < n) { dst += copy; sector += copy >> SECTOR_SHIFT; copy = n - copy; + rcu_read_lock(); page = brd_lookup_page(brd, sector); if (page) { src = kmap_atomic(page); @@ -201,6 +208,7 @@ static void copy_from_brd(void *dst, str kunmap_atomic(src); } else memset(dst, 0, copy); + rcu_read_unlock(); } }
This patch extends the rcu regions, so that lookup followed by a read or write of a page is done inside rcu read lock. This is needed for the following patch that enables discard. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> --- drivers/block/brd.c | 8 ++++++++ 1 file changed, 8 insertions(+)