From 2e86e154da23b3067fa579b530a8f057be6a391e Mon Sep 17 00:00:00 2001 From: Noah Misch Date: Fri, 10 Jan 2020 18:31:22 -0800 Subject: [PATCH] Maintain valid md.c state when FileClose() fails. FileClose() failure ordinarily causes a PANIC. Suppose the user disables that PANIC via data_sync_retry=on. After mdclose() issued a FileClose() that failed, calls into md.c raised SIGSEGV. This fix adds repalloc() calls during mdclose(); update a comment about ignoring repalloc() cost. The rate of relation segment count change is a minor factor; more relevant to overall performance is the rate of mdclose() and subsequent re-opening of segments. Back-patch to v10, where commit 45e191e3aa62d47a8bc1a33f784286b2051f45cb introduced the bug. Reviewed by Kyotaro Horiguchi. Discussion: https://postgr.es/m/20191222091930.GA1280238@rfd.leadboat.com --- src/backend/storage/smgr/md.c | 20 ++++++-------------- 1 file changed, 6 insertions(+), 14 deletions(-) diff --git a/src/backend/storage/smgr/md.c b/src/backend/storage/smgr/md.c index 2e6127f7a2..200cc7f657 100644 --- a/src/backend/storage/smgr/md.c +++ b/src/backend/storage/smgr/md.c @@ -638,18 +638,10 @@ mdclose(SMgrRelation reln, ForkNumber forknum) { MdfdVec *v = &reln->md_seg_fds[forknum][nopensegs - 1]; - /* if not closed already */ - if (v->mdfd_vfd >= 0) - { - FileClose(v->mdfd_vfd); - v->mdfd_vfd = -1; - } - + FileClose(v->mdfd_vfd); + _fdvec_resize(reln, forknum, nopensegs - 1); nopensegs--; } - - /* resize just once, avoids pointless reallocations */ - _fdvec_resize(reln, forknum, 0); } /* @@ -1773,10 +1765,10 @@ _fdvec_resize(SMgrRelation reln, else { /* - * It doesn't seem worthwhile complicating the code by having a more - * aggressive growth strategy here; the number of segments doesn't - * grow that fast, and the memory context internally will sometimes - * avoid doing an actual reallocation. + * It doesn't seem worthwhile complicating the code to amortize + * repalloc() calls. Those are far faster than PathNameOpenFile() or + * FileClose(), and the memory context internally will sometimes avoid + * doing an actual reallocation. */ reln->md_seg_fds[forknum] = repalloc(reln->md_seg_fds[forknum],