From 9609c9a153232fb2de169bf76158781d354c633b Mon Sep 17 00:00:00 2001 From: Thomas Munro Date: Fri, 13 Dec 2019 17:12:42 +1300 Subject: [PATCH] Don't use _mdfd_getseg() in mdsyncfiletag(). _mdfd_getseg() opens all segments up to the requested one. That causes problems for mdsyncfiletag(), if mdunlinkfork() has already unlinked other segment files. Open the file we want directly by name instead, if we don't have it already. The consequence of this bug was a rare panic in the checkpointer, made more likely if you saturated the sync request queue so that the SYNC_FORGET_REQUEST messages for a given relation were more likely to be absorbed in separate cycles by the checkpointer. Back-patch to 12. Defect in commit 3eb77eba. Author: Thomas Munro Reported-by: Justin Pryzby Discussion: https://postgr.es/m/20191119115759.GI30362%40telsasoft.com --- src/backend/storage/smgr/md.c | 56 ++++++++++++++++++++++++----------- 1 file changed, 39 insertions(+), 17 deletions(-) diff --git a/src/backend/storage/smgr/md.c b/src/backend/storage/smgr/md.c index 8a9eaf6430..1a7b91b523 100644 --- a/src/backend/storage/smgr/md.c +++ b/src/backend/storage/smgr/md.c @@ -1280,25 +1280,47 @@ int mdsyncfiletag(const FileTag *ftag, char *path) { SMgrRelation reln = smgropen(ftag->rnode, InvalidBackendId); - MdfdVec *v; - char *p; + int fd, + result, + save_errno; + bool need_to_close; - /* Provide the path for informational messages. */ - p = _mdfd_segpath(reln, ftag->forknum, ftag->segno); - strlcpy(path, p, MAXPGPATH); - pfree(p); + /* See if we already have the file open, or need to open it. */ + if (ftag->segno < reln->md_num_open_segs[ftag->forknum]) + { + File file = reln->md_seg_fds[ftag->forknum][ftag->segno].mdfd_vfd; + + strlcpy(path, FilePathName(file), MAXPGPATH); + fd = FileGetRawDesc(file); + need_to_close = false; + } + else + { + char *p; + + p = _mdfd_segpath(reln, ftag->forknum, ftag->segno); + strlcpy(path, p, MAXPGPATH); + pfree(p); + + fd = OpenTransientFile(path, O_RDWR); + if (fd < 0) + return -1; + need_to_close = true; + } + + /* Sync the file. */ + pgstat_report_wait_start(WAIT_EVENT_DATA_FILE_SYNC); + result = pg_fsync(fd); + save_errno = errno; + pgstat_report_wait_end(); + + if (need_to_close && CloseTransientFile(fd) != 0) + ereport(WARNING, + (errcode_for_file_access(), + errmsg("could not close file \"%s\": %m", path))); + errno = save_errno; - /* Try to open the requested segment. */ - v = _mdfd_getseg(reln, - ftag->forknum, - ftag->segno * (BlockNumber) RELSEG_SIZE, - false, - EXTENSION_RETURN_NULL | EXTENSION_DONT_CHECK_SIZE); - if (v == NULL) - return -1; - - /* Try to fsync the file. */ - return FileSync(v->mdfd_vfd, WAIT_EVENT_DATA_FILE_SYNC); + return result; } /* -- 2.24.0