Remove misleading hint for "unexpected data beyond EOF" error.

Commit ffae5cc5a6024b4e25ec920ed5c4dfac649605f8 added this hint in 2006,
but it's now obsolete and doesn't reflect what users should really check
in this situation. We were not able to agree on a new hint, so just delete
the existing one and update the comments to mention one possibility that
is known to cause problems of this kind: something other than PostgreSQL
is modifying files in the PostgreSQL data directory.

Author: Jakub Wartak <jakub.wartak@enterprisedb.com>
Reviewed-by: Robert Haas <rhaas@postgresql.org>
Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Christoph Berg <myon@debian.org>
Discussion: https://postgr.es/m/CAKZiRmxNbcaL76x=09Sxf7aUmrRQJBf8drzDdUHo+j9_eM+VMg@mail.gmail.com

diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index 6afdd28dba6f2dc137a1a2a56d4183e63feb740d..9c6fe587ec94032b0b509cd4af1a9328cbb30866 100644 (file)
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -2743,11 +2743,9 @@ ExtendBufferedRelShared(BufferManagerRelation bmr,
                 * because mdread doesn't complain about reads beyond EOF (when
                 * zero_damaged_pages is ON) and so a previous attempt to read a block
                 * beyond EOF could have left a "valid" zero-filled buffer.
-                * Unfortunately, we have also seen this case occurring because of
-                * buggy Linux kernels that sometimes return an lseek(SEEK_END) result
-                * that doesn't account for a recent write. In that situation, the
-                * pre-existing buffer would contain valid data that we don't want to
-                * overwrite.  Since the legitimate cases should always have left a
+                *
+                * This has also been observed when relation was overwritten by external
+                * process. Since the legitimate cases should always have left a
                 * zero-filled buffer, complain if not PageIsNew.
                 */
                if (existing_id >= 0)
@@ -2778,8 +2776,7 @@ ExtendBufferedRelShared(BufferManagerRelation bmr,
                                ereport(ERROR,
                                                (errmsg("unexpected data beyond EOF in block %u of relation %s",
                                                                existing_hdr->tag.blockNum,
-                                                               relpath(bmr.smgr->smgr_rlocator, fork).str),
-                                                errhint("This has been seen to occur with buggy kernels; consider updating your system.")));
+                                                               relpath(bmr.smgr->smgr_rlocator, fork).str)));
 
                        /*
                         * We *must* do smgr[zero]extend before succeeding, else the page