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ref: dcbb9930ea0098005a4d8e0c6b2e299e10bf7e5f
parent: 9600b2bd0271198a18f5acc22ed5f8bda43b3618
author: Ori Bernstein <ori@eigenstate.org>
date: Mon Oct 27 10:25:37 EDT 2025 

gefs: ensure all tree access is wrapped in an epoch

technically, some of the write-only accesses may have been
safe, but lets be conservative.


--- a/sys/src/cmd/gefs/cons.c
+++ b/sys/src/cmd/gefs/cons.c
@@ -417,10 +417,10 @@
 	{.name="halt",		.sub=nil,	.minarg=0, .maxarg=0, .fn=haltfs},
 	{.name="help",		.sub=nil,	.minarg=0, .maxarg=0, .fn=help},
 	{.name="permit",	.sub=nil,	.minarg=1, .maxarg=1, .fn=permflip},
-	{.name="snap",		.sub=nil,	.minarg=1, .maxarg=3, .fn=snapfs},
+	{.name="snap",		.sub=nil,	.minarg=1, .maxarg=3, .fn=snapfs, .epoch=1},
 	{.name="sync",		.sub=nil,	.minarg=0, .maxarg=0, .fn=syncfs},
 	{.name="reserve",	.sub=nil,	.minarg=0, .maxarg=1, .fn=unreserve},
-	{.name="users",		.sub=nil,	.minarg=0, .maxarg=1, .fn=refreshusers},
+	{.name="users",		.sub=nil,	.minarg=0, .maxarg=1, .fn=refreshusers, .epoch=1},
 
 	/* debugging */
 	{.name="show",		.sub="fid",	.minarg=0, .maxarg=0, .fn=showfid},
--- a/sys/src/cmd/gefs/fs.c
+++ b/sys/src/cmd/gefs/fs.c
@@ -80,7 +80,7 @@
 }
 
 static void
-sync(void)
+sync(int id)
 {
 	Mount *mnt;
 	Arena *a;
@@ -98,7 +98,7 @@
 		nexterror();
 	}
 
-	/* 
+	/*
 	 * Wait for data that we're syncing to hit disk
 	 */
 	tracem("flush1");
@@ -112,7 +112,9 @@
 	 *  can take a consistent snapshot.
          */
 	qlock(&fs->mutlk);
+	epochstart(id);
 	if(waserror()){
+		epochend(id);
 		aincl(&fs->rdonly, 1);
 		qunlock(&fs->mutlk);
 		nexterror();
@@ -162,6 +164,7 @@
 	finalize(fs->sb0);
 	finalize(fs->sb1);
 	fs->snap.dirty = 0;
+	epochend(id);
 	qunlock(&fs->mutlk);
 	poperror();
 
@@ -2819,7 +2822,7 @@
 					epochwait();
 					epochclean();
 				}
-				sync();
+				sync(id);
 			}
 			postnote(PNGROUP, getpid(), "halted");
 			exits(nil);
@@ -2861,7 +2864,7 @@
 				epochclean();
 			}
 
-			sync();	/* oldhd blocks leaked on error() */
+			sync(id);	/* oldhd blocks leaked on error() */
 
 			for(i = 0; i < fs->narena; i++){
 				for(bp = oldhd[i]; bp.addr != -1; bp = nb){
@@ -2915,7 +2918,7 @@
 			qunlock(&fs->mutlk);
 			poperror();
 
-			sync();	/* t leaked on error() */
+			sync(id);	/* t leaked on error() */
 
 			if(t != nil){
 				epochwait();
-- 
⑨