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Avoid holding a directory FD open across assorted SRF calls.

Browse Source 
This extends the fixes made in commit 085b6b667 to other SRFs with the
same bug, namely pg_logdir_ls(), pgrowlocks(), pg_timezone_names(),
pg_ls_dir(), and pg_tablespace_databases().

Also adjust various comments and documentation to warn against
expecting to clean up resources during a ValuePerCall SRF's final
call.

Back-patch to all supported branches, since these functions were
all born broken.

Justin Pryzby, with cosmetic tweaks by me

Discussion: https://postgr.es/m/20200308173103.GC1357@telsasoft.com
This commit is contained in:
Tom Lane
2020-03-16 21:05:28 -04:00
parent 113758155c
commit b4570d33aa
10 changed files with 386 additions and 346 deletions
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125
src/backend/utils/adt/misc.c
View File

@@ -194,72 +194,82 @@ current_query(PG_FUNCTION_ARGS)
/* Function to find out which databases make use of a tablespace */
typedef struct
{
char *location;
DIR *dirdesc;
} ts_db_fctx;
Datum
pg_tablespace_databases(PG_FUNCTION_ARGS)
{
FuncCallContext *funcctx;
Oid tablespaceOid = PG_GETARG_OID(0);
ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
bool randomAccess;
TupleDesc tupdesc;
Tuplestorestate *tupstore;
char *location;
DIR *dirdesc;
struct dirent *de;
ts_db_fctx *fctx;
MemoryContext oldcontext;
if (SRF_IS_FIRSTCALL())
/* check to see if caller supports us returning a tuplestore */
if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("set-valued function called in context that cannot accept a set")));
if (!(rsinfo->allowedModes & SFRM_Materialize))
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("materialize mode required, but it is not allowed in this context")));
/* The tupdesc and tuplestore must be created in ecxt_per_query_memory */
oldcontext = MemoryContextSwitchTo(rsinfo->econtext->ecxt_per_query_memory);
tupdesc = CreateTemplateTupleDesc(1);
TupleDescInitEntry(tupdesc, (AttrNumber) 1, "pg_tablespace_databases",
OIDOID, -1, 0);
randomAccess = (rsinfo->allowedModes & SFRM_Materialize_Random) != 0;
tupstore = tuplestore_begin_heap(randomAccess, false, work_mem);
rsinfo->returnMode = SFRM_Materialize;
rsinfo->setResult = tupstore;
rsinfo->setDesc = tupdesc;
MemoryContextSwitchTo(oldcontext);
if (tablespaceOid == GLOBALTABLESPACE_OID)
{
MemoryContext oldcontext;
Oid tablespaceOid = PG_GETARG_OID(0);
funcctx = SRF_FIRSTCALL_INIT();
oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
fctx = palloc(sizeof(ts_db_fctx));
if (tablespaceOid == GLOBALTABLESPACE_OID)
{
fctx->dirdesc = NULL;
ereport(WARNING,
(errmsg("global tablespace never has databases")));
}
else
{
if (tablespaceOid == DEFAULTTABLESPACE_OID)
fctx->location = psprintf("base");
else
fctx->location = psprintf("pg_tblspc/%u/%s", tablespaceOid,
TABLESPACE_VERSION_DIRECTORY);
fctx->dirdesc = AllocateDir(fctx->location);
if (!fctx->dirdesc)
{
/* the only expected error is ENOENT */
if (errno != ENOENT)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not open directory \"%s\": %m",
fctx->location)));
ereport(WARNING,
(errmsg("%u is not a tablespace OID", tablespaceOid)));
}
}
funcctx->user_fctx = fctx;
MemoryContextSwitchTo(oldcontext);
ereport(WARNING,
(errmsg("global tablespace never has databases")));
/* return empty tuplestore */
return (Datum) 0;
}
funcctx = SRF_PERCALL_SETUP();
fctx = (ts_db_fctx *) funcctx->user_fctx;
if (tablespaceOid == DEFAULTTABLESPACE_OID)
location = psprintf("base");
else
location = psprintf("pg_tblspc/%u/%s", tablespaceOid,
TABLESPACE_VERSION_DIRECTORY);
if (!fctx->dirdesc) /* not a tablespace */
SRF_RETURN_DONE(funcctx);
dirdesc = AllocateDir(location);
while ((de = ReadDir(fctx->dirdesc, fctx->location)) != NULL)
if (!dirdesc)
{
/* the only expected error is ENOENT */
if (errno != ENOENT)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not open directory \"%s\": %m",
location)));
ereport(WARNING,
(errmsg("%u is not a tablespace OID", tablespaceOid)));
/* return empty tuplestore */
return (Datum) 0;
}
while ((de = ReadDir(dirdesc, location)) != NULL)
{
Oid datOid = atooid(de->d_name);
char *subdir;
bool isempty;
Datum values[1];
bool nulls[1];
/* this test skips . and .., but is awfully weak */
if (!datOid)
@@ -267,18 +277,21 @@ pg_tablespace_databases(PG_FUNCTION_ARGS)
/* if database subdir is empty, don't report tablespace as used */
subdir = psprintf("%s/%s", fctx->location, de->d_name);
subdir = psprintf("%s/%s", location, de->d_name);
isempty = directory_is_empty(subdir);
pfree(subdir);
if (isempty)
continue; /* indeed, nothing in it */
SRF_RETURN_NEXT(funcctx, ObjectIdGetDatum(datOid));
values[0] = ObjectIdGetDatum(datOid);
nulls[0] = false;
tuplestore_putvalues(tupstore, tupdesc, values, nulls);
}
FreeDir(fctx->dirdesc);
SRF_RETURN_DONE(funcctx);
FreeDir(dirdesc);
return (Datum) 0;
}