[bug #48169] find makes unnecessary syscalls

[anonymous]

URL:
  <http://savannah.gnu.org/bugs/?48169>

                 Summary: find makes unnecessary syscalls
                 Project: findutils
            Submitted by: None
            Submitted on: Wed 08 Jun 2016 01:10:23 AM UTC
                Category: find
                Severity: 3 - Normal
              Item Group: None
                  Status: None
                 Privacy: Public
             Assigned to: None
         Originator Name: Tavian Barnes
        Originator Email: address@hidden
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 4.6.0
           Fixed Release: None

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Details:

$ mkdir -p foo/bar/baz
$ strace find foo >/dev/null
...
newfstatat(5, "bar", {st_mode=S_IFDIR|0755, st_size=6, ...},
AT_SYMLINK_NOFOLLOW) = 0
fcntl(5, F_DUPFD_CLOEXEC, 0)            = 4
openat(5, "bar", O_RDONLY|O_NOCTTY|O_NONBLOCK|O_DIRECTORY|O_NOFOLLOW) = 6
fcntl(6, F_GETFD)                       = 0
fcntl(6, F_SETFD, FD_CLOEXEC)           = 0
fstat(6, {st_mode=S_IFDIR|0755, st_size=6, ...}) = 0
fcntl(6, F_GETFL)                       = 0x38800 (flags
O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_DIRECTORY|O_NOFOLLOW)
fcntl(6, F_SETFD, FD_CLOEXEC)           = 0
newfstatat(5, "bar", {st_mode=S_IFDIR|0755, st_size=6, ...},
AT_SYMLINK_NOFOLLOW) = 0
fcntl(6, F_DUPFD, 3)                    = 7
fcntl(7, F_GETFD)                       = 0
fcntl(7, F_SETFD, FD_CLOEXEC)           = 0
getdents(6, /* 3 entries */, 32768)     = 72
getdents(6, /* 0 entries */, 32768)     = 0
close(6)                                = 0
newfstatat(7, "baz", {st_mode=S_IFDIR|0755, st_size=0, ...},
AT_SYMLINK_NOFOLLOW) = 0
close(4)                                = 0
...

In particular:

- fd 4 is unused
- fcntl(6, F_SETFD, FD_CLOEXEC) happens twice, but could be totally avoided
with O_CLOEXEC (I suspect the second one is from within fdopendir() though)
- newfstatat(5, "bar", AT_SYMLINK_NOFOLLOW) happens twice
- fcntl(7, F_SETFD, FD_CLOEXEC) could be avoided if fcntl(6, F_DUPFD_CLOEXEC)
were used

This seems new with 4.6, at least 4.4 didn't do this.




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