From c4f52c8cabb35d7db6d24681227146a195688c39 Mon Sep 17 00:00:00 2001 From: Thomas Munro Date: Wed, 27 Jul 2022 18:01:12 +1200 Subject: [PATCH] Fix read_relmap_file() concurrency on Windows. Commit d8cd0c6c introduced a file rename that could fail on Windows due to other backends reading an old file of the same name. Re-arrange the locking slightly to prevent that. Discussion: https://postgr.es/m/CA%2BhUKGLZtCTgp4NTWV-wGbR2Nyag71%3DEfYTKjDKnk%2BfkhuFMHw%40mail.gmail.com --- src/backend/utils/cache/relmapper.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) diff --git a/src/backend/utils/cache/relmapper.c b/src/backend/utils/cache/relmapper.c index 79e09181b6..4562a0ad6f 100644 --- a/src/backend/utils/cache/relmapper.c +++ b/src/backend/utils/cache/relmapper.c @@ -788,16 +788,6 @@ read_relmap_file(RelMapFile *map, char *dbpath, bool lock_held, int elevel) Assert(elevel >= ERROR); - /* Open the target file. */ - snprintf(mapfilename, sizeof(mapfilename), "%s/%s", dbpath, - RELMAPPER_FILENAME); - fd = OpenTransientFile(mapfilename, O_RDONLY | PG_BINARY); - if (fd < 0) - ereport(elevel, - (errcode_for_file_access(), - errmsg("could not open file \"%s\": %m", - mapfilename))); - /* * Grab the lock to prevent the file from being updated while we read it, * unless the caller is already holding the lock. If the file is updated @@ -808,6 +798,16 @@ read_relmap_file(RelMapFile *map, char *dbpath, bool lock_held, int elevel) if (!lock_held) LWLockAcquire(RelationMappingLock, LW_SHARED); + /* Open the target file. */ + snprintf(mapfilename, sizeof(mapfilename), "%s/%s", dbpath, + RELMAPPER_FILENAME); + fd = OpenTransientFile(mapfilename, O_RDONLY | PG_BINARY); + if (fd < 0) + ereport(elevel, + (errcode_for_file_access(), + errmsg("could not open file \"%s\": %m", + mapfilename))); + /* Now read the data. */ pgstat_report_wait_start(WAIT_EVENT_RELATION_MAP_READ); r = read(fd, map, sizeof(RelMapFile)); -- 2.35.1