On 05/22, Amir Goldstein wrote:
> On Fri, May 22, 2020 at 4:06 AM Arvind Raghavan
> <raghavan.arvind@xxxxxxxxx> wrote:
> >
> > On 05/21, Amir Goldstein wrote:
> > > On Thu, May 21, 2020 at 3:10 AM Arvind Raghavan
> > > <raghavan.arvind@xxxxxxxxx> wrote:
> > > >
> > > > Allow regular links and symlinks to be passed as input to fssum.
> > > >
> > > > Signed-off-by: Arvind Raghavan <raghavan.arvind@xxxxxxxxx>
> > > > Signed-off-by: Jayashree Mohan <jaya@xxxxxxxxxxxxx>
> > > > Signed-off-by: Vijay Chidambaram <vijay@xxxxxxxxxxxxx>
> > > > ---
> > > > src/fssum.c | 35 ++++++++++++++++++++++++++++++++++-
> > > > 1 file changed, 34 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/src/fssum.c b/src/fssum.c
> > > > index ece0f556..2d1624ca 100644
> > > > --- a/src/fssum.c
> > > > +++ b/src/fssum.c
> > > > @@ -29,6 +29,7 @@
> > > > #include <inttypes.h>
> > > > #include <assert.h>
> > > > #include <endian.h>
> > > > +#include <libgen.h>
> > > >
> > > > #define CS_SIZE 16
> > > > #define CHUNKS 128
> > > > @@ -884,8 +885,40 @@ main(int argc, char *argv[])
> > > > if (gen_manifest)
> > > > fprintf(out_fp, "Flags: %s\n", flagstring);
> > > >
> > > > + struct stat64 path_st;
> > > > + if (fstat64(fd, &path_st)) {
> > > > + perror("fstat");
> > > > + exit(-1);
> > > > + }
> > > > +
> > > > sum_init(&cs);
> > > > - sum(fd, 1, &cs, path, "");
> > > > +
> > > > + if (S_ISDIR(path_st.st_mode)) {
> > > > + sum(fd, 1, &cs, path, "");
> > > > + } else if (S_ISREG(path_st.st_mode) || S_ISLNK(path_st.st_mode)) {
> > > > + // Copy because dirname may modify path
> > > > + char* path_copy = alloc(strlen(path));
> > > > + strcpy(path_copy, path);
>
> If you stay with this code please use strdup().
>
> > > > +
> > > > + char* dir_path = dirname(path);
> > > > + char* name = basename(path_copy);
> > > > +
> > > > + int dirfd = open(dir_path, O_RDONLY);
> > > > + if (fd == -1) {
> > > > + fprintf(stderr, "failed to open %s: %s\n", dir_path,
> > > > + strerror(errno));
> > > > + exit(-1);
> > > > + }
> > > > +
> > > > + sum_one(dirfd, 1, &cs, dir_path, "", name);
> > >
> > > Instead of all of the above, how about just:
> > > sum_one(fd, 1, &cs, path, "", "");
> > >
> > > From looking at sum_one() code, it seems to me like that will work,
> > > but I may be missing something.
> > > It's not that you *want* the name in the checksum, it is not even
> > > part of the metadata that is being synced with fsync.
> >
> > The issue here is that we preserved the code from sum which does
> > all its opens using openat with the parent directory fd and a
> > filename. Since we're trying to reuse that code I believe we need
> > to have this somewhat ugly boilerplate.
>
> Ok. But if you stay with this please add a comment about why
> this is done with a hint for the future how to fix this properly.
>
> Or (up to you) you can fix it by calling this helper instead of openat():
>
> int open_one(int dirfd, const char *name)
> {
> if (!name || !*name)
> return dup(dirfd);
> return openat(dirfd, name, 0);
> }
>
> fstatat() can take empty name with AT_EMPTY_PATH flag.
> readlinkat() should be able to take an empty name, but documentation
> is not clear whether fd must be O_PATH - need to verify if it works with
> non O_PATH fd.
I might be doing something wrong but I can't seem to get
AT_EMPTY_PATH to work with fstatat. I don't see it on the man
page and when I pass it to fstatat it errors out with invalid
argument.
In the case that fstatat doesn't support AT_EMPTY_PATH, do you
see another way to fix the above code?
Thanks,
Arvind
