Fix unlinking of SLRU segments.

Commit dee663f7 intended to drop any queued up fsync requests before
unlinking segment files, but missed a code path.  Fix, by centralizing
the forget-and-unlink code into a single function.

Reported-by: Tomas Vondra <[email protected]>
Discussion: https://postgr.es/m/20201104013205.icogbi773przyny5%40development

diff --git a/src/backend/access/transam/slru.c b/src/backend/access/transam/slru.c
index 16a78986971ff51085c7ea94a5cc7517e834e33a..cec17cb2aec0e2c7ff0b32099f9d444837670853 100644 (file)
--- a/src/backend/access/transam/slru.c
+++ b/src/backend/access/transam/slru.c
@@ -145,7 +145,7 @@ static int  SlruSelectLRUPage(SlruCtl ctl, int pageno);
 
 static bool SlruScanDirCbDeleteCutoff(SlruCtl ctl, char *filename,
                                      int segpage, void *data);
-static void SlruInternalDeleteSegment(SlruCtl ctl, char *filename);
+static void SlruInternalDeleteSegment(SlruCtl ctl, int segno);
 
 /*
  * Initialization of shared memory
@@ -1298,19 +1298,28 @@ restart:;
 }
 
 /*
- * Delete an individual SLRU segment, identified by the filename.
+ * Delete an individual SLRU segment.
  *
  * NB: This does not touch the SLRU buffers themselves, callers have to ensure
  * they either can't yet contain anything, or have already been cleaned out.
  */
 static void
-SlruInternalDeleteSegment(SlruCtl ctl, char *filename)
+SlruInternalDeleteSegment(SlruCtl ctl, int segno)
 {
    char        path[MAXPGPATH];
 
-   snprintf(path, MAXPGPATH, "%s/%s", ctl->Dir, filename);
-   ereport(DEBUG2,
-           (errmsg("removing file \"%s\"", path)));
+   /* Forget any fsync requests queued for this segment. */
+   if (ctl->sync_handler != SYNC_HANDLER_NONE)
+   {
+       FileTag     tag;
+
+       INIT_SLRUFILETAG(tag, ctl->sync_handler, segno);
+       RegisterSyncRequest(&tag, SYNC_FORGET_REQUEST, true);
+   }
+
+   /* Unlink the file. */
+   SlruFileName(ctl, path, segno);
+   ereport(DEBUG2, (errmsg("removing file \"%s\"", path)));
    unlink(path);
 }
 
@@ -1322,7 +1331,6 @@ SlruDeleteSegment(SlruCtl ctl, int segno)
 {
    SlruShared  shared = ctl->shared;
    int         slotno;
-   char        path[MAXPGPATH];
    bool        did_write;
 
    /* Clean out any possibly existing references to the segment. */
@@ -1364,23 +1372,7 @@ restart:
    if (did_write)
        goto restart;
 
-   snprintf(path, MAXPGPATH, "%s/%04X", ctl->Dir, segno);
-   ereport(DEBUG2,
-           (errmsg("removing file \"%s\"", path)));
-
-   /*
-    * Tell the checkpointer to forget any sync requests, before we unlink the
-    * file.
-    */
-   if (ctl->sync_handler != SYNC_HANDLER_NONE)
-   {
-       FileTag     tag;
-
-       INIT_SLRUFILETAG(tag, ctl->sync_handler, segno);
-       RegisterSyncRequest(&tag, SYNC_FORGET_REQUEST, true);
-   }
-
-   unlink(path);
+   SlruInternalDeleteSegment(ctl, segno);
 
    LWLockRelease(shared->ControlLock);
 }
@@ -1413,7 +1405,7 @@ SlruScanDirCbDeleteCutoff(SlruCtl ctl, char *filename, int segpage, void *data)
    int         cutoffPage = *(int *) data;
 
    if (ctl->PagePrecedes(segpage, cutoffPage))
-       SlruInternalDeleteSegment(ctl, filename);
+       SlruInternalDeleteSegment(ctl, segpage / SLRU_PAGES_PER_SEGMENT);
 
    return false;               /* keep going */
 }
@@ -1425,7 +1417,7 @@ SlruScanDirCbDeleteCutoff(SlruCtl ctl, char *filename, int segpage, void *data)
 bool
 SlruScanDirCbDeleteAll(SlruCtl ctl, char *filename, int segpage, void *data)
 {
-   SlruInternalDeleteSegment(ctl, filename);
+   SlruInternalDeleteSegment(ctl, segpage / SLRU_PAGES_PER_SEGMENT);
 
    return false;               /* keep going */
 }