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Commit 912ad922 authored by Paolo 'Blaisorblade' Giarrusso's avatar Paolo 'Blaisorblade' Giarrusso Committed by Linus Torvalds
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[PATCH] uml: fix not_dead_yet when directory is in bad state 



The bug occurred to me when a UML left an empty ~/.uml/Sarge-norm folder -
when trying to reuse not_dead_yet() failed one of its check.  The comment
says that's ok and means that we can take the directory, but while normally
not_dead_yet() removes it and returns 0 (i.e.  go on, use this), on failure
it returns 0 but forgets to remove it.  The fix is to remove it anytime
we're going to return 0.

But since "not_dead_yet" didn't make the interface so clear, causing this
bug, and I couldn't find a convenient name for the mix of things it did, I
split it into two parts:

is_umdir_used()      -	returns a boolean, contains all checks of not_dead_yet()
umdir_take_if_dead   -	tries to remove the dir unless it's used - returns
			whether it removed it, that is we now own it.

With this changes the control flow is IMHO a bit clearer and needs less
comment for control flow.

Signed-off-by: default avatarPaolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Cc: Jeff Dike <jdike@addtoit.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 47e5243a

arch/um/os-Linux/umid.c

+29 −19
Original line number Diff line number Diff line
@@ -103,9 +103,10 @@ static int actually_do_remove(char *dir) 
 * 	something other than UML sticking stuff in the directory

 *	this boot racing with a shutdown of the other UML

 * In any of these cases, the directory isn't useful for anything else.

 *

 * Boolean return: 1 if in use, 0 otherwise.

 */



static int not_dead_yet(char *dir)

static inline int is_umdir_used(char *dir)

{

	char file[strlen(uml_dir) + UMID_LEN + sizeof("/pid\0")];

	char pid[sizeof("nnnnn\0")], *end;
@@ -113,7 +114,7 @@ static int not_dead_yet(char *dir) 


	n = snprintf(file, sizeof(file), "%s/pid", dir);

	if(n >= sizeof(file)){

		printk("not_dead_yet - pid filename too long\n");

		printk("is_umdir_used - pid filename too long\n");

		err = -E2BIG;

		goto out;

	}
@@ -123,7 +124,7 @@ static int not_dead_yet(char *dir) 
	if(fd < 0) {

		fd = -errno;

		if(fd != -ENOENT){

			printk("not_dead_yet : couldn't open pid file '%s', "

			printk("is_umdir_used : couldn't open pid file '%s', "

			       "err = %d\n", file, -fd);

		}

		goto out;
@@ -132,18 +133,18 @@ static int not_dead_yet(char *dir) 
	err = 0;

	n = read(fd, pid, sizeof(pid));

	if(n < 0){

		printk("not_dead_yet : couldn't read pid file '%s', "

		printk("is_umdir_used : couldn't read pid file '%s', "

		       "err = %d\n", file, errno);

		goto out_close;

	} else if(n == 0){

		printk("not_dead_yet : couldn't read pid file '%s', "

		printk("is_umdir_used : couldn't read pid file '%s', "

		       "0-byte read\n", file);

		goto out_close;

	}



	p = strtoul(pid, &end, 0);

	if(end == pid){

		printk("not_dead_yet : couldn't parse pid file '%s', "

		printk("is_umdir_used : couldn't parse pid file '%s', "

		       "errno = %d\n", file, errno);

		goto out_close;

	}
@@ -153,19 +154,32 @@ static int not_dead_yet(char *dir) 
		return 1;

	}



	err = actually_do_remove(dir);

	if(err)

		printk("not_dead_yet - actually_do_remove failed with "

		       "err = %d\n", err);



	return err;



out_close:

	close(fd);

out:

	return 0;

}



/*

 * Try to remove the directory @dir unless it's in use.

 * Precondition: @dir exists.

 * Returns 0 for success, < 0 for failure in removal or if the directory is in

 * use.

 */

static int umdir_take_if_dead(char *dir)

{

	int ret;

	if (is_umdir_used(dir))

		return -EEXIST;



	ret = actually_do_remove(dir);

	if (ret) {

		printk("is_umdir_used - actually_do_remove failed with "

		       "err = %d\n", ret);

	}

	return ret;

}



static void __init create_pid_file(void)

{

	char file[strlen(uml_dir) + UMID_LEN + sizeof("/pid\0")];
@@ -244,11 +258,7 @@ int __init make_umid(void) 
		if(err != -EEXIST)

			goto err;



		/* 1   -> this umid is already in use

		 * < 0 -> we couldn't remove the umid directory

		 * In either case, we can't use this umid, so return -EEXIST.

		 */

		if(not_dead_yet(tmp) != 0)

		if (umdir_take_if_dead(tmp) < 0)

			goto err;



		err = mkdir(tmp, 0777);