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Linux kernel source tree
b64af6bcd3
Customer reported that one of their applications started failing to
open files with STATUS_INSUFFICIENT_RESOURCES due to NetApp server
hitting the maximum number of opens to same file that it would allow
for a single client connection.
It turned out the client was failing to reuse open handles with
deferred closes because matching ->f_flags directly without masking
off O_CREAT|O_EXCL|O_TRUNC bits first broke the comparision and then
client ended up with thousands of deferred closes to same file. Those
bits are already satisfied on the original open, so no need to check
them against existing open handles.
Reproducer:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <pthread.h>
#define NR_THREADS 4
#define NR_ITERATIONS 2500
#define TEST_FILE "/mnt/1/test/dir/foo"
static char buf[64];
static void *worker(void *arg)
{
int i, j;
int fd;
for (i = 0; i < NR_ITERATIONS; i++) {
fd = open(TEST_FILE, O_WRONLY|O_CREAT|O_APPEND, 0666);
for (j = 0; j < 16; j++)
write(fd, buf, sizeof(buf));
close(fd);
}
}
int main(int argc, char *argv[])
{
pthread_t t[NR_THREADS];
int fd;
int i;
fd = open(TEST_FILE, O_WRONLY|O_CREAT|O_TRUNC, 0666);
close(fd);
memset(buf, 'a', sizeof(buf));
for (i = 0; i < NR_THREADS; i++)
pthread_create(&t[i], NULL, worker, NULL);
for (i = 0; i < NR_THREADS; i++)
pthread_join(t[i], NULL);
return 0;
}
Before patch:
$ mount.cifs //srv/share /mnt/1 -o ...
$ mkdir -p /mnt/1/test/dir
$ gcc repro.c && ./a.out
...
number of opens: 1391
After patch:
$ mount.cifs //srv/share /mnt/1 -o ...
$ mkdir -p /mnt/1/test/dir
$ gcc repro.c && ./a.out
...
number of opens: 1
Cc: linux-cifs@vger.kernel.org
Cc: David Howells <dhowells@redhat.com>
Cc: Jay Shin <jaeshin@redhat.com>
Cc: Pierguido Lambri <plambri@redhat.com>
Fixes:
|
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .clippy.toml | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .pylintrc | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.