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 <tomas.vondra@2ndquadrant.com>
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 */
 }