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Josh Durgin
4e752f0ab0
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>