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s3:smbd: let openat_pathref_dirfsp_nosymlink() try VFS_OPEN_HOW_RESOLVE_NO_SYMLINKS first

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This will reduce the amount of syscalls and the related cost drastically
for long path names.

Pair-Programmed-With: Stefan Metzmacher <metze@samba.org>

Signed-off-by: Volker Lendecke <vl@samba.org>
Signed-off-by: Stefan Metzmacher <metze@samba.org>
This commit is contained in:
Volker Lendecke 2022-07-14 19:44:04 +02:00
parent 35b99c87ef
commit d6653067b2
1 changed files with 64 additions and 0 deletions
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64
source3/smbd/files.c
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@ -820,6 +820,69 @@ NTSTATUS openat_pathref_dirfsp_nosymlink(
rel_fname.base_name = next;
}
if (conn->open_how_resolve & VFS_OPEN_HOW_RESOLVE_NO_SYMLINKS) {
/*
* Try a direct openat2 with RESOLVE_NO_SYMLINKS to
* avoid the openat/close loop further down.
*/
rel_fname.base_name = discard_const_p(char, path_in);
how.resolve = VFS_OPEN_HOW_RESOLVE_NO_SYMLINKS;
fd = SMB_VFS_OPENAT(conn, dirfsp, &rel_fname, fsp, &how);
if (fd >= 0) {
fsp_set_fd(fsp, fd);
TALLOC_FREE(full_fname.base_name);
full_fname = rel_fname;
goto done;
}
status = map_nt_error_from_unix(errno);
DBG_DEBUG("SMB_VFS_OPENAT(%s, %s, RESOLVE_NO_SYMLINKS) returned %d %s => %s\n",
smb_fname_str_dbg(dirfsp->fsp_name), path_in,
errno, strerror(errno), nt_errstr(status));
SMB_ASSERT(fd == -1);
switch (errno) {
case ENOSYS:
/*
* We got ENOSYS, so fallback to the old code
* if the kernel doesn't support openat2() yet.
*/
break;
case ELOOP:
case ENOTDIR:
/*
* For ELOOP we also fallback in order to
* return the correct information with
* NT_STATUS_STOPPED_ON_SYMLINK.
*
* O_NOFOLLOW|O_DIRECTORY results in
* ENOTDIR instead of ELOOP for the final
* component.
*/
break;
case ENOENT:
/*
* If we got ENOENT, the filesystem could
* be case sensitive. For now we only do
* the get_real_filename_at() dance in
* the fallback loop below.
*/
break;
default:
goto fail;
}
/*
* Just fallback to the openat loop
*/
how.resolve = 0;
}
/*
* Now we loop over all components
* opening each one and using it
@ -967,6 +1030,7 @@ next:
dirfsp = NULL;
}
done:
fsp->fsp_flags.is_pathref = true;
fsp->fsp_name = NULL;