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 a263875fd5a25e640905ceaf598d61c67b63e635..a44a34eeae1802925560d83da5f97e0eaa323318 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)