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OpenCloudOS-Kernel
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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: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Cc: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Paolo 'Blaisorblade' Giarrusso 2006-07-01 04:36:23 -07:00 committed by Linus Torvalds
parent 47e5243afe
commit 912ad92220
1 changed files with 29 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

48
arch/um/os-Linux/umid.c
View File

@ -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);