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files: Add ability to use read link in dump_one_reg_file

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To be able to dump procfs namespace entries we will need to
analyze the link name first and then figure out if the file
referred indeed a procfs entry or it's plain regular file.

This means we read link early, and to escape double reading
of same link, once we read it we remember it in fd_parms
structure which we pass to dump_one_reg_file.

Still the dump_one_reg_file is not solely used from inside
of dump_one_file, but from a number of other places (fifo,
special files) where fd_parms is filled only partially
and fill_fd_params is not even called. Thus dump_one_reg_file
must be ready for such scenario and read the link name by own
if the caller has not provided one.

To achieve all this we do

 - extend fd_parms structure to have a reference on a new
   fd_link structure, thus if caller already read the link
   name it might assign the reference and call for dump_one_reg_file

 - tune up dump_one_reg_file to fill own copy of fd_link
   structure if the caller has not provied one

  [ xemul: Added const to fill_fdlink arg ]

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
This commit is contained in:
Cyrill Gorcunov
2013-05-20 13:30:16 +04:00
committed by Pavel Emelyanov
parent 19ce784db5
commit 4531f0ac7d
3 changed files with 46 additions and 13 deletions
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25
files.c
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@@ -135,6 +135,22 @@ int do_dump_gen_file(struct fd_parms *p, int lfd,
return pb_write_one(fdinfo, &e, PB_FDINFO);
}
int fill_fdlink(int lfd, const struct fd_parms *p, struct fd_link *link)
{
size_t len;
link->name[0] = '.';
len = read_fd_link(lfd, &link->name[1], sizeof(link->name) - 1);
if (len < 0) {
pr_err("Can't read link for pid %d fd %d\n", p->pid, p->fd);
return -1;
}
link->len = len + 1;
return 0;
}
static int fill_fd_params(struct parasite_ctl *ctl, int fd, int lfd,
struct fd_opts *opts, struct fd_parms *p)
{
@@ -244,8 +260,15 @@ static int dump_one_file(struct parasite_ctl *ctl, int fd, int lfd, struct fd_op
return dump_unsupp_fd(&p);
}
if (S_ISREG(p.stat.st_mode) || S_ISDIR(p.stat.st_mode))
if (S_ISREG(p.stat.st_mode) || S_ISDIR(p.stat.st_mode)) {
struct fd_link link;
if (fill_fdlink(lfd, &p, &link))
return -1;
p.link = &link;
return dump_reg_file(&p, lfd, fdinfo);
}
if (S_ISFIFO(p.stat.st_mode)) {
if (statfs.f_type == PIPEFS_MAGIC)