Use the correct sizeof() in BufFileLoadBuffer

The sizeof() call should reference buffer.data, because that's the
buffer we're reading data into, not the whole PGAlignedBuffer union.
This was introduced by 44cac93464, which replaced the simple buffer
with a PGAlignedBuffer field.

It's benign, because the buffer is the largest field of the union, so
the sizes are the same. But it's easy to trip over this in a patch, so
fix and backpatch. Commit 44cac93464 went into 12, but that's EOL.

Backpatch-through: 13
Discussion: https://postgr.es/m/928bdab1-6567-449f-98c4-339cd2203b87@vondra.me

diff --git a/src/backend/storage/file/buffile.c b/src/backend/storage/file/buffile.c
index 6449f82a72bdc283f145864b7c85392641f5cf5f..a4541b87b8fd3a35230a4a5e5ab648612c6e60ac 100644 (file)
--- a/src/backend/storage/file/buffile.c
+++ b/src/backend/storage/file/buffile.c
@@ -459,7 +459,7 @@ BufFileLoadBuffer(BufFile *file)
     */
    file->nbytes = FileRead(thisfile,
                            file->buffer.data,
-                           sizeof(file->buffer),
+                           sizeof(file->buffer.data),
                            file->curOffset,
                            WAIT_EVENT_BUFFILE_READ);
    if (file->nbytes < 0)