shithub: gefs

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fs: go readonly when running check to prevent deadlocks

a long running check holds the epoch open for a long time,
so if a mutator is generating a lot of garbage, we can run
out of cache blocks and deadlock; this prevents mutation
until the check has finished to prevent this.

--- a/check.c

+++ b/check.c

@@ -2,6 +2,7 @@

 #include <libc.h>

 #include <fcall.h>

 #include <avl.h>

+#include <atomic.h>

 #include "dat.h"

 #include "fns.h"

@@ -182,6 +183,8 @@

 	Blk *b;

 	ok = 1;

+	aincl(&fs->rdonly, 1);

+	epochwait();

 	if(waserror()){

 		fprint(fd, "error checking %s\n", errmsg());

 		return 0;

@@ -220,6 +223,7 @@

 		poperror();

 	}

 	btexit(&s);

+	aincl(&fs->rdonly, -1);

 	poperror();

 	return ok;

 }