On Fri, Aug 25, 2017 at 11:56 PM, Wangkai (Kevin,C)
<wangkai86@xxxxxxxxxx> wrote:
>
> but I am worried, if there are programs create,delete many temporary files and unique,
> the negative dentries will keep growing.
The thing is, this has nothing to do with unlink.
The *easiest* way to generate negative dentries is in fact to never
create any files at all: just look up millions of non-existent names.
IOW, just something like this
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
int main()
{
int i;
for (i = 0; i < 10000000; i++) {
char name[20];
struct stat st;
snprintf(name, sizeof(name), "n:%d", i);
stat(name, &st);
}
return 0;
}
is a much easier and faster way to create negative dentries.
And yes, it's entirely possible that we could/should have some way to
balance negative dentries against positive ones, but on the whole this
has not really come up as a huge problem.
For example, your module that does a lot of GFP_ATOMIC allocations -
if it wasn't for dentries, it would have been something else.
GFP_ATOMIC *will* fail after a while, because it just can't replenish
the free memory. That's fundamental. That's what GFP_ATOMIC _means_.
It's very much meant for "occasional critical allocations", and if you
do just GFP_ATOMIC, you will fail.
Linus
