[dm-devel] [PATCH v3 2/4] brd: extend the rcu regions to cover read and write
Mikulas Patocka
mpatocka at redhat.com
Thu Aug 10 10:09:11 UTC 2023
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 at redhat.com>
---
drivers/block/brd.c | 8 ++++++++
1 file changed, 8 insertions(+)
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();
}
}
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