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Commita712487

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Fix transient mdsync() errors of truncated relations due to72a98a6.
Unfortunately the segment size checks from72a98a6 had the negativeside-effect of breaking a corner case in mdsync(): When processing afsync request for a truncated away segment mdsync() could fail with"could not fsync file" (if previous segment < RELSEG_SIZE) because_mdfd_getseg() now wouldn't return the relevant segment anymore.The cleanest fix seems to be to allow the caller of _mdfd_getseg() tospecify whether checks for RELSEG_SIZE are performed. To allow doing so,change the ExtensionBehavior enum into a bitmask. Besides allowing forthe addition of EXTENSION_DONT_CHECK_SIZE, this makes for a nicerimplementation of EXTENSION_REALLY_RETURN_NULL.Besides mdsync() the only callsite that should change behaviour due tothis is mdprefetch() which now doesn't create segments anymore, even inrecovery. Given the uses of mdprefetch() that seems better.Reported-By: Thom BrownDiscussion: CAA-aLv72QazLvPdKZYpVn4a_Eh+i4_cxuB03k+iCuZM_xjc+6Q@mail.gmail.com
1 parent613fb29 commita712487

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1 file changed

+47
-34
lines changed
  • src/backend/storage/smgr

1 file changed

+47
-34
lines changed

‎src/backend/storage/smgr/md.c‎

Lines changed: 47 additions & 34 deletions
Original file line numberDiff line numberDiff line change
@@ -163,23 +163,29 @@ static CycleCtr mdsync_cycle_ctr = 0;
163163
staticCycleCtrmdckpt_cycle_ctr=0;
164164

165165

166-
typedefenum/* behavior for mdopen & _mdfd_getseg */
167-
{
168-
/* ereport if segment not present, create in recovery */
169-
EXTENSION_FAIL,
170-
/* return NULL if not present, create in recovery */
171-
EXTENSION_RETURN_NULL,
172-
/* return NULL if not present */
173-
EXTENSION_REALLY_RETURN_NULL,
174-
/* create new segments as needed */
175-
EXTENSION_CREATE
176-
}ExtensionBehavior;
166+
/*** behavior for mdopen & _mdfd_getseg ***/
167+
/* ereport if segment not present */
168+
#defineEXTENSION_FAIL(1 << 0)
169+
/* return NULL if segment not present */
170+
#defineEXTENSION_RETURN_NULL(1 << 1)
171+
/* create new segments as needed */
172+
#defineEXTENSION_CREATE(1 << 2)
173+
/* create new segments if needed during recovery */
174+
#defineEXTENSION_CREATE_RECOVERY(1 << 3)
175+
/*
176+
* Allow opening segments which are preceded by segments smaller than
177+
* RELSEG_SIZE, e.g. inactive segments (see above). Note that this is breaks
178+
* mdnblocks() and related functionality henceforth - which currently is ok,
179+
* because this is only required in the checkpointer which never uses
180+
* mdnblocks().
181+
*/
182+
#defineEXTENSION_DONT_CHECK_SIZE(1 << 4)
183+
177184

178185
/* local routines */
179186
staticvoidmdunlinkfork(RelFileNodeBackendrnode,ForkNumberforkNum,
180187
boolisRedo);
181-
staticMdfdVec*mdopen(SMgrRelationreln,ForkNumberforknum,
182-
ExtensionBehaviorbehavior);
188+
staticMdfdVec*mdopen(SMgrRelationreln,ForkNumberforknum,intbehavior);
183189
staticvoidregister_dirty_segment(SMgrRelationreln,ForkNumberforknum,
184190
MdfdVec*seg);
185191
staticvoidregister_unlink(RelFileNodeBackendrnode);
@@ -189,7 +195,7 @@ static char *_mdfd_segpath(SMgrRelation reln, ForkNumber forknum,
189195
staticMdfdVec*_mdfd_openseg(SMgrRelationreln,ForkNumberforkno,
190196
BlockNumbersegno,intoflags);
191197
staticMdfdVec*_mdfd_getseg(SMgrRelationreln,ForkNumberforkno,
192-
BlockNumberblkno,boolskipFsync,ExtensionBehaviorbehavior);
198+
BlockNumberblkno,boolskipFsync,intbehavior);
193199
staticBlockNumber_mdnblocks(SMgrRelationreln,ForkNumberforknum,
194200
MdfdVec*seg);
195201

@@ -570,7 +576,7 @@ mdextend(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum,
570576
* invent one out of whole cloth.
571577
*/
572578
staticMdfdVec*
573-
mdopen(SMgrRelationreln,ForkNumberforknum,ExtensionBehaviorbehavior)
579+
mdopen(SMgrRelationreln,ForkNumberforknum,intbehavior)
574580
{
575581
MdfdVec*mdfd;
576582
char*path;
@@ -596,8 +602,7 @@ mdopen(SMgrRelation reln, ForkNumber forknum, ExtensionBehavior behavior)
596602
fd=PathNameOpenFile(path,O_RDWR |O_CREAT |O_EXCL |PG_BINARY,0600);
597603
if (fd<0)
598604
{
599-
if ((behavior==EXTENSION_RETURN_NULL||
600-
behavior==EXTENSION_REALLY_RETURN_NULL)&&
605+
if ((behavior&EXTENSION_RETURN_NULL)&&
601606
FILE_POSSIBLY_DELETED(errno))
602607
{
603608
pfree(path);
@@ -690,8 +695,8 @@ mdwriteback(SMgrRelation reln, ForkNumber forknum,
690695
intsegnum_start,
691696
segnum_end;
692697

693-
v=_mdfd_getseg(reln,forknum,blocknum,false,
694-
EXTENSION_REALLY_RETURN_NULL);
698+
v=_mdfd_getseg(reln,forknum,blocknum,true/* not used */,
699+
EXTENSION_RETURN_NULL);
695700

696701
/*
697702
* We might be flushing buffers of already removed relations, that's
@@ -737,7 +742,8 @@ mdread(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum,
737742
reln->smgr_rnode.node.relNode,
738743
reln->smgr_rnode.backend);
739744

740-
v=_mdfd_getseg(reln,forknum,blocknum, false,EXTENSION_FAIL);
745+
v=_mdfd_getseg(reln,forknum,blocknum, false,
746+
EXTENSION_FAIL |EXTENSION_CREATE_RECOVERY);
741747

742748
seekpos= (off_t)BLCKSZ*(blocknum % ((BlockNumber)RELSEG_SIZE));
743749

@@ -812,7 +818,8 @@ mdwrite(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum,
812818
reln->smgr_rnode.node.relNode,
813819
reln->smgr_rnode.backend);
814820

815-
v=_mdfd_getseg(reln,forknum,blocknum,skipFsync,EXTENSION_FAIL);
821+
v=_mdfd_getseg(reln,forknum,blocknum,skipFsync,
822+
EXTENSION_FAIL |EXTENSION_CREATE_RECOVERY);
816823

817824
seekpos= (off_t)BLCKSZ*(blocknum % ((BlockNumber)RELSEG_SIZE));
818825

@@ -1219,7 +1226,9 @@ mdsync(void)
12191226
/* Attempt to open and fsync the target segment */
12201227
seg=_mdfd_getseg(reln,forknum,
12211228
(BlockNumber)segno* (BlockNumber)RELSEG_SIZE,
1222-
false,EXTENSION_RETURN_NULL);
1229+
false,
1230+
EXTENSION_RETURN_NULL
1231+
|EXTENSION_DONT_CHECK_SIZE);
12231232

12241233
INSTR_TIME_SET_CURRENT(sync_start);
12251234

@@ -1773,14 +1782,18 @@ _mdfd_openseg(SMgrRelation reln, ForkNumber forknum, BlockNumber segno,
17731782
*/
17741783
staticMdfdVec*
17751784
_mdfd_getseg(SMgrRelationreln,ForkNumberforknum,BlockNumberblkno,
1776-
boolskipFsync,ExtensionBehaviorbehavior)
1785+
boolskipFsync,intbehavior)
17771786
{
17781787
MdfdVec*v=mdopen(reln,forknum,behavior);
17791788
BlockNumbertargetseg;
17801789
BlockNumbernextsegno;
17811790

1791+
/* some way to handle non-existant segments needs to be specified */
1792+
Assert(behavior&
1793+
(EXTENSION_FAIL |EXTENSION_CREATE |EXTENSION_RETURN_NULL));
1794+
17821795
if (!v)
1783-
returnNULL;/* ifEXTENSION_(REALLY_)RETURN_NULL */
1796+
returnNULL;/* ifbehavior & EXTENSION_RETURN_NULL */
17841797

17851798
targetseg=blkno / ((BlockNumber)RELSEG_SIZE);
17861799
for (nextsegno=1;nextsegno <=targetseg;nextsegno++)
@@ -1795,8 +1808,8 @@ _mdfd_getseg(SMgrRelation reln, ForkNumber forknum, BlockNumber blkno,
17951808
if (nblocks> ((BlockNumber)RELSEG_SIZE))
17961809
elog(FATAL,"segment too big");
17971810

1798-
if (behavior==EXTENSION_CREATE||
1799-
(InRecovery&&behavior!=EXTENSION_REALLY_RETURN_NULL))
1811+
if ((behavior&EXTENSION_CREATE)||
1812+
(InRecovery&&(behavior&EXTENSION_CREATE_RECOVERY)))
18001813
{
18011814
/*
18021815
* Normally we will create new segments only if authorized by
@@ -1827,15 +1840,16 @@ _mdfd_getseg(SMgrRelation reln, ForkNumber forknum, BlockNumber blkno,
18271840
}
18281841
flags=O_CREAT;
18291842
}
1830-
elseif (nblocks< ((BlockNumber)RELSEG_SIZE))
1843+
elseif (!(behavior&EXTENSION_DONT_CHECK_SIZE)&&
1844+
nblocks< ((BlockNumber)RELSEG_SIZE))
18311845
{
18321846
/*
1833-
* When not extending, only open the next segment if the
1834-
* current one is exactly RELSEG_SIZE. If not (this branch),
1835-
* either return NULL or fail.
1847+
* When not extending (or explicitly including truncated
1848+
* segments), only open the next segment if the current one is
1849+
* exactly RELSEG_SIZE. If not (this branch), either return
1850+
* NULL or fail.
18361851
*/
1837-
if (behavior==EXTENSION_RETURN_NULL||
1838-
behavior==EXTENSION_REALLY_RETURN_NULL)
1852+
if (behavior&EXTENSION_RETURN_NULL)
18391853
{
18401854
/*
18411855
* Some callers discern between reasons for _mdfd_getseg()
@@ -1858,8 +1872,7 @@ _mdfd_getseg(SMgrRelation reln, ForkNumber forknum, BlockNumber blkno,
18581872

18591873
if (v->mdfd_chain==NULL)
18601874
{
1861-
if ((behavior==EXTENSION_RETURN_NULL||
1862-
behavior==EXTENSION_REALLY_RETURN_NULL)&&
1875+
if ((behavior&EXTENSION_RETURN_NULL)&&
18631876
FILE_POSSIBLY_DELETED(errno))
18641877
returnNULL;
18651878
ereport(ERROR,

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