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authorJosh Durgin <josh.durgin@inktank.com>2014-04-08 11:12:11 -0700
committerIlya Dryomov <idryomov@redhat.com>2014-10-14 21:03:27 +0400
commit4e752f0ab0e8114f4edd7574081dc625d679dd15 (patch)
tree80ef03b61b96c8eacf052607f28fcea03d5cce9f /drivers/block
parent7dd440c9e0711d828442c3e129ab8bcb9aeeac23 (diff)
rbd: access snapshot context and mapping size safely
These fields may both change while the image is mapped if a snapshot is created or deleted or the image is resized. They are guarded by rbd_dev->header_rwsem, so hold that while reading them, and store a local copy to refer to outside of the critical section. The local copy will stay consistent since the snapshot context is reference counted, and the mapping size is just a u64. This prevents torn loads from giving us inconsistent values. Move reading header.snapc into the caller of rbd_img_request_create() so that we only need to take the semaphore once. The read-only caller, rbd_parent_request_create() can just pass NULL for snapc, since the snapshot context is only relevant for writes. Signed-off-by: Josh Durgin <josh.durgin@inktank.com>
Diffstat (limited to 'drivers/block')
-rw-r--r--drivers/block/rbd.c34
1 files changed, 21 insertions, 13 deletions
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index ce457db5d847..eea44ce2d537 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -2057,7 +2057,8 @@ static bool rbd_dev_parent_get(struct rbd_device *rbd_dev)
static struct rbd_img_request *rbd_img_request_create(
struct rbd_device *rbd_dev,
u64 offset, u64 length,
- bool write_request)
+ bool write_request,
+ struct ceph_snap_context *snapc)
{
struct rbd_img_request *img_request;
@@ -2065,12 +2066,6 @@ static struct rbd_img_request *rbd_img_request_create(
if (!img_request)
return NULL;
- if (write_request) {
- down_read(&rbd_dev->header_rwsem);
- ceph_get_snap_context(rbd_dev->header.snapc);
- up_read(&rbd_dev->header_rwsem);
- }
-
img_request->rq = NULL;
img_request->rbd_dev = rbd_dev;
img_request->offset = offset;
@@ -2078,7 +2073,7 @@ static struct rbd_img_request *rbd_img_request_create(
img_request->flags = 0;
if (write_request) {
img_request_write_set(img_request);
- img_request->snapc = rbd_dev->header.snapc;
+ img_request->snapc = snapc;
} else {
img_request->snap_id = rbd_dev->spec->snap_id;
}
@@ -2134,8 +2129,8 @@ static struct rbd_img_request *rbd_parent_request_create(
rbd_assert(obj_request->img_request);
rbd_dev = obj_request->img_request->rbd_dev;
- parent_request = rbd_img_request_create(rbd_dev->parent,
- img_offset, length, false);
+ parent_request = rbd_img_request_create(rbd_dev->parent, img_offset,
+ length, false, NULL);
if (!parent_request)
return NULL;
@@ -3183,9 +3178,11 @@ out:
static void rbd_handle_request(struct rbd_device *rbd_dev, struct request *rq)
{
struct rbd_img_request *img_request;
+ struct ceph_snap_context *snapc = NULL;
u64 offset = (u64)blk_rq_pos(rq) << SECTOR_SHIFT;
u64 length = blk_rq_bytes(rq);
bool wr = rq_data_dir(rq) == WRITE;
+ u64 mapping_size;
int result;
/* Ignore/skip any zero-length requests */
@@ -3226,14 +3223,23 @@ static void rbd_handle_request(struct rbd_device *rbd_dev, struct request *rq)
goto err_rq; /* Shouldn't happen */
}
- if (offset + length > rbd_dev->mapping.size) {
+ down_read(&rbd_dev->header_rwsem);
+ mapping_size = rbd_dev->mapping.size;
+ if (wr) {
+ snapc = rbd_dev->header.snapc;
+ ceph_get_snap_context(snapc);
+ }
+ up_read(&rbd_dev->header_rwsem);
+
+ if (offset + length > mapping_size) {
rbd_warn(rbd_dev, "beyond EOD (%llu~%llu > %llu)", offset,
- length, rbd_dev->mapping.size);
+ length, mapping_size);
result = -EIO;
goto err_rq;
}
- img_request = rbd_img_request_create(rbd_dev, offset, length, wr);
+ img_request = rbd_img_request_create(rbd_dev, offset, length, wr,
+ snapc);
if (!img_request) {
result = -ENOMEM;
goto err_rq;
@@ -3256,6 +3262,8 @@ err_rq:
if (result)
rbd_warn(rbd_dev, "%s %llx at %llx result %d",
wr ? "write" : "read", length, offset, result);
+ if (snapc)
+ ceph_put_snap_context(snapc);
blk_end_request_all(rq, result);
}