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 1b37062321a6bddbcb0d9570cb56d17f5acff883..46d32e180de2319947aac1d577d5a9680755dd3d 100644 (file)
--- a/src/backend/storage/file/buffile.c
+++ b/src/backend/storage/file/buffile.c
@@ -430,7 +430,7 @@ BufFileLoadBuffer(BufFile *file)
        thisfile = file->files[file->curFile];
        file->nbytes = FileRead(thisfile,
                                                        file->buffer.data,
-                                                       sizeof(file->buffer),
+                                                       sizeof(file->buffer.data),
                                                        file->curOffset,
                                                        WAIT_EVENT_BUFFILE_READ);
        if (file->nbytes < 0)