Fix RBM_ZERO_AND_LOCK.
Commit 210622c6 accidentally zeroed out pages even if they were found in
the buffer pool. It should always lock the page, but it should only
zero pages that were not already valid. Otherwise, concurrent readers
that hold only a pin could see corrupted page contents changing under
their feet.
While here, rename ZeroAndLockBuffer() to match the RBM_ flag name.
Also restore a some useful comments lost by 210622c6's refactoring, and
add some new ones to clarify why we need to use the BM_IO_IN_PROGRESS
infrastructure despite not doing I/O.
Reported-by: Noah Misch <noah@leadboat.com>
Reported-by: Alexander Lakhin <exclusion@gmail.com>
Reviewed-by: Alvaro Herrera <alvherre@alvh.no-ip.org> (earlier version)
Reviewed-by: Robert Haas <robertmhaas@gmail.com> (earlier version)
Discussion: https://postgr.es/m/20240512171658.7e.nmisch@google.com
Discussion: https://postgr.es/m/7ed10231-ce47-03d5-d3f9-4aea0dc7d5a4%40gmail.com
Branch
------
master
Details
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https://git.postgresql.org/pg/commitdiff/e656657f2b93a96b83fd4038ec5120c5ec9845e5
Modified Files
--------------
src/backend/storage/buffer/bufmgr.c | 88 ++++++++++++++++++++++++++++---------
1 file changed, 67 insertions(+), 21 deletions(-)
