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charset="UTF-8" Content-Transfer-Encoding: 7bit X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.883,Hydra:6.0.517,FMLib:17.11.122.1 definitions=2022-08-16_07,2022-08-16_01,2022-06-22_01 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/15/22 12:00 PM, Christian Brauner wrote: > !-------------------------------------------------------------------| > This Message Is From an External Sender > > |-------------------------------------------------------------------! > > On Mon, Aug 15, 2022 at 12:32:25PM +0800, kernel test robot wrote: >> >> >> Greeting, >> >> FYI, we noticed a -9.0% regression of will-it-scale.per_thread_ops due to commit: >> >> >> commit: faf99b563558f74188b7ca34faae1c1da49a7261 ("fs: add __remove_file_privs() with flags parameter") >> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master > > This seems overall pretty odd tbh at least it's not immediately obvious > how that specific commit would've caused this. But fwiw, I think there's > one issue in this change which we originally overlooked which might > explain this. > > Before faf99b563558 ("fs: add __remove_file_privs() with flags > parameter") inode_has_no_xattr() was called when > dentry_needs_remove_privs() returned 0. > > int error = 0 > [...] > kill = dentry_needs_remove_privs(dentry); > if (kill < 0) > return kill; > if (kill) > error = __remove_privs(file_mnt_user_ns(file), dentry, kill); > if (!error) > inode_has_no_xattr(inode); > > but now we do: > > kill = dentry_needs_remove_privs(dentry); > if (kill <= 0) > return kill; > > which means we don't call inode_has_no_xattr(). I don't think that we > did this intentionally. inode_has_no_xattr() just sets S_NOSEC which > means next time we call into __file_remove_privs() we can return earlier > instead of hitting dentry_needs_remove_privs() again: > > if (IS_NOSEC(inode) || !S_ISREG(inode->i_mode)) > return 0; > > So I think that needs to be fixed? > Christian, thanks for looking into this. I'll prepare a fix to maintain the original behavior. --Stefan > Christian