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criu/file-ids.c

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files: Use sys_kcmp to find file descriptor duplicates v4 We switch generic-object-id concept with sys_kcmp approach, which implies changes of image format a bit (and since it's early time for project overall, we're allowed to). In short -- previously every file descriptor had an ID generated by a kernel and exported via procfs. If the appropriate file descriptors were the same objects in kernel memory -- the IDs did match up to bit. It allows us to figure out which files were actually the identical ones and should be restored in a special way. Once sys_kcmp system call was merged into the kernel, we've got a new opprotunity -- to use this syscall instead. The syscall basically compares kernel objects and returns ordered results suitable for objects sorting in a userspace. For us it means -- we treat every file descriptor as a combination of 'genid' and 'subid'. While 'genid' serves for fast comparison between fds, the 'subid' is kind of a second key, which guarantees uniqueness of genid+subid tuple over all file descritors found in a process (or group of processes). To be able to find and dump file descriptors in a single pass we collect every fd into a global rbtree, where (!) each node might become a root for a subtree as well. The main tree carries only non-equal genid. If we find genid which is already in tree, we need to make sure that it's either indeed a duplicate or not. For this we use sys_kcmp syscall and if we find that file descriptors are different -- we simply put new fd into a subtree. Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org> Acked-by: Pavel Emelyanov <xemul@parallels.com>
2012-02-28 18:27:28 +04:00
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <signal.h>
#include <limits.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include "asm/types.h"
files: Use sys_kcmp to find file descriptor duplicates v4 We switch generic-object-id concept with sys_kcmp approach, which implies changes of image format a bit (and since it's early time for project overall, we're allowed to). In short -- previously every file descriptor had an ID generated by a kernel and exported via procfs. If the appropriate file descriptors were the same objects in kernel memory -- the IDs did match up to bit. It allows us to figure out which files were actually the identical ones and should be restored in a special way. Once sys_kcmp system call was merged into the kernel, we've got a new opprotunity -- to use this syscall instead. The syscall basically compares kernel objects and returns ordered results suitable for objects sorting in a userspace. For us it means -- we treat every file descriptor as a combination of 'genid' and 'subid'. While 'genid' serves for fast comparison between fds, the 'subid' is kind of a second key, which guarantees uniqueness of genid+subid tuple over all file descritors found in a process (or group of processes). To be able to find and dump file descriptors in a single pass we collect every fd into a global rbtree, where (!) each node might become a root for a subtree as well. The main tree carries only non-equal genid. If we find genid which is already in tree, we need to make sure that it's either indeed a duplicate or not. For this we use sys_kcmp syscall and if we find that file descriptors are different -- we simply put new fd into a subtree. Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org> Acked-by: Pavel Emelyanov <xemul@parallels.com>
2012-02-28 18:27:28 +04:00
#include "file-ids.h"
#include "rbtree.h"
#include "kcmp-ids.h"
files: Use sys_kcmp to find file descriptor duplicates v4 We switch generic-object-id concept with sys_kcmp approach, which implies changes of image format a bit (and since it's early time for project overall, we're allowed to). In short -- previously every file descriptor had an ID generated by a kernel and exported via procfs. If the appropriate file descriptors were the same objects in kernel memory -- the IDs did match up to bit. It allows us to figure out which files were actually the identical ones and should be restored in a special way. Once sys_kcmp system call was merged into the kernel, we've got a new opprotunity -- to use this syscall instead. The syscall basically compares kernel objects and returns ordered results suitable for objects sorting in a userspace. For us it means -- we treat every file descriptor as a combination of 'genid' and 'subid'. While 'genid' serves for fast comparison between fds, the 'subid' is kind of a second key, which guarantees uniqueness of genid+subid tuple over all file descritors found in a process (or group of processes). To be able to find and dump file descriptors in a single pass we collect every fd into a global rbtree, where (!) each node might become a root for a subtree as well. The main tree carries only non-equal genid. If we find genid which is already in tree, we need to make sure that it's either indeed a duplicate or not. For this we use sys_kcmp syscall and if we find that file descriptors are different -- we simply put new fd into a subtree. Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org> Acked-by: Pavel Emelyanov <xemul@parallels.com>
2012-02-28 18:27:28 +04:00
#include "compiler.h"
#include "syscall.h"
#include "image.h"
#include "util.h"
static DECLARE_KCMP_TREE(fd_tree, KCMP_FILE);
void fd_id_show_tree(void)
{
kid_show_tree(&fd_tree);
}
u32 fd_id_generate_special(void)
{
return fd_tree.subid++;
}
int fd_id_generate(pid_t pid, FdinfoEntry *fe)
{
u32 id;
struct kid_elem e;
int new_id = 0;
e.pid = pid;
e.genid = fe->id;
e.idx = fe->fd;
id = kid_generate_gen(&fd_tree, &e, &new_id);
if (!id)
return -ENOMEM;
fe->id = id;
return new_id;
files: Use sys_kcmp to find file descriptor duplicates v4 We switch generic-object-id concept with sys_kcmp approach, which implies changes of image format a bit (and since it's early time for project overall, we're allowed to). In short -- previously every file descriptor had an ID generated by a kernel and exported via procfs. If the appropriate file descriptors were the same objects in kernel memory -- the IDs did match up to bit. It allows us to figure out which files were actually the identical ones and should be restored in a special way. Once sys_kcmp system call was merged into the kernel, we've got a new opprotunity -- to use this syscall instead. The syscall basically compares kernel objects and returns ordered results suitable for objects sorting in a userspace. For us it means -- we treat every file descriptor as a combination of 'genid' and 'subid'. While 'genid' serves for fast comparison between fds, the 'subid' is kind of a second key, which guarantees uniqueness of genid+subid tuple over all file descritors found in a process (or group of processes). To be able to find and dump file descriptors in a single pass we collect every fd into a global rbtree, where (!) each node might become a root for a subtree as well. The main tree carries only non-equal genid. If we find genid which is already in tree, we need to make sure that it's either indeed a duplicate or not. For this we use sys_kcmp syscall and if we find that file descriptors are different -- we simply put new fd into a subtree. Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org> Acked-by: Pavel Emelyanov <xemul@parallels.com>
2012-02-28 18:27:28 +04:00
}