This patch extends rcu read sections, so that all manipulations of the
page and its data are within read sections.
This patch is a prerequisite for discarding pages using rcu.
Note that the page pointer escapes the rcu section in the function
brd_direct_access, however, direct access is not supposed to race with
discard.
Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
---
drivers/block/brd.c | 19 +++++++++++++++++--
1 file changed, 17 insertions(+), 2 deletions(-)
Index: linux-2.6/drivers/block/brd.c
===================================================================
--- linux-2.6.orig/drivers/block/brd.c
+++ linux-2.6/drivers/block/brd.c
@@ -71,10 +71,8 @@ static struct page *brd_lookup_page(stru
* safe here (we don't have total exclusion from radix tree updates
* here, only deletes).
*/
- rcu_read_lock();
idx = sector >> PAGE_SECTORS_SHIFT; /* sector to page index */
page = radix_tree_lookup(&brd->brd_pages, idx);
- rcu_read_unlock();
BUG_ON(page && page->index != idx);
@@ -92,7 +90,12 @@ static struct page *brd_insert_page(stru
struct page *page;
gfp_t gfp_flags;
+ rcu_read_lock();
+
page = brd_lookup_page(brd, sector);
+
+ rcu_read_unlock();
+
if (page)
return page;
@@ -151,9 +154,13 @@ static void brd_zero_page(struct brd_dev
{
struct page *page;
+ rcu_read_lock();
+
page = brd_lookup_page(brd, sector);
if (page)
clear_highpage(page);
+
+ rcu_read_unlock();
}
/*
@@ -246,6 +253,8 @@ static void copy_to_brd(struct brd_devic
unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT;
size_t copy;
+ rcu_read_lock();
+
copy = min_t(size_t, n, PAGE_SIZE - offset);
page = brd_lookup_page(brd, sector);
BUG_ON(!page);
@@ -265,6 +274,8 @@ static void copy_to_brd(struct brd_devic
memcpy(dst, src, copy);
kunmap_atomic(dst);
}
+
+ rcu_read_unlock();
}
/*
@@ -278,6 +289,8 @@ static void copy_from_brd(void *dst, str
unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT;
size_t copy;
+ rcu_read_lock();
+
copy = min_t(size_t, n, PAGE_SIZE - offset);
page = brd_lookup_page(brd, sector);
if (page) {
@@ -299,6 +312,8 @@ static void copy_from_brd(void *dst, str
} else
memset(dst, 0, copy);
}
+
+ rcu_read_unlock();
}
/*
--
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