Pull misc vfs updates from Christian Brauner: "This contains the usual miscellaneous features, cleanups, and fixes for vfs and individual fses. Features: - Rename and export helpers that get write access to a mount. They are used in overlayfs to get write access to the upper mount. - Print the pretty name of the root device on boot failure. This helps in scenarios where we would usually only print "unknown-block(1,2)". - Add an internal SB_I_NOUMASK flag. This is another part in the endless POSIX ACL saga in a way. When POSIX ACLs are enabled via SB_POSIXACL the vfs cannot strip the umask because if the relevant inode has POSIX ACLs set it might take the umask from there. But if the inode doesn't have any POSIX ACLs set then we apply the umask in the filesytem itself. So we end up with: (1) no SB_POSIXACL -> strip umask in vfs (2) SB_POSIXACL -> strip umask in filesystem The umask semantics associated with SB_POSIXACL allowed filesystems that don't even support POSIX ACLs at all to raise SB_POSIXACL purely to avoid umask stripping. That specifically means NFS v4 and Overlayfs. NFS v4 does it because it delegates this to the server and Overlayfs because it needs to delegate umask stripping to the upper filesystem, i.e., the filesystem used as the writable layer. This went so far that SB_POSIXACL is raised eve on kernels that don't even have POSIX ACL support at all. Stop this blatant abuse and add SB_I_NOUMASK which is an internal superblock flag that filesystems can raise to opt out of umask handling. That should really only be the two mentioned above. It's not that we want any filesystems to do this. Ideally we have all umask handling always in the vfs. - Make overlayfs use SB_I_NOUMASK too. - Now that we have SB_I_NOUMASK, stop checking for SB_POSIXACL in IS_POSIXACL() if the kernel doesn't have support for it. This is a very old patch but it's only possible to do this now with the wider cleanup that was done. - Follow-up work on fake path handling from last cycle. Citing mostly from Amir: When overlayfs was first merged, overlayfs files of regular files and directories, the ones that are installed in file table, had a "fake" path, namely, f_path is the overlayfs path and f_inode is the "real" inode on the underlying filesystem. In v6.5, we took another small step by introducing of the backing_file container and the file_real_path() helper. This change allowed vfs and filesystem code to get the "real" path of an overlayfs backing file. With this change, we were able to make fsnotify work correctly and report events on the "real" filesystem objects that were accessed via overlayfs. This method works fine, but it still leaves the vfs vulnerable to new code that is not aware of files with fake path. A recent example is commit db1d1e8b9867 ("IMA: use vfs_getattr_nosec to get the i_version"). This commit uses direct referencing to f_path in IMA code that otherwise uses file_inode() and file_dentry() to reference the filesystem objects that it is measuring. This contains work to switch things around: instead of having filesystem code opt-in to get the "real" path, have generic code opt-in for the "fake" path in the few places that it is needed. Is it far more likely that new filesystems code that does not use the file_dentry() and file_real_path() helpers will end up causing crashes or averting LSM/audit rules if we keep the "fake" path exposed by default. This change already makes file_dentry() moot, but for now we did not change this helper just added a WARN_ON() in ovl_d_real() to catch if we have made any wrong assumptions. After the dust settles on this change, we can make file_dentry() a plain accessor and we can drop the inode argument to ->d_real(). - Switch struct file to SLAB_TYPESAFE_BY_RCU. This looks like a small change but it really isn't and I would like to see everyone on their tippie toes for any possible bugs from this work. Essentially we've been doing most of what SLAB_TYPESAFE_BY_RCU for files since a very long time because of the nasty interactions between the SCM_RIGHTS file descriptor garbage collection. So extending it makes a lot of sense but it is a subtle change. There are almost no places that fiddle with file rcu semantics directly and the ones that did mess around with struct file internal under rcu have been made to stop doing that because it really was always dodgy. I forgot to put in the link tag for this change and the discussion in the commit so adding it into the merge message: https://lore.kernel.org/r/20230926162228.68666-1-mjguzik@gmail.com Cleanups: - Various smaller pipe cleanups including the removal of a spin lock that was only used to protect against writes without pipe_lock() from O_NOTIFICATION_PIPE aka watch queues. As that was never implemented remove the additional locking from pipe_write(). - Annotate struct watch_filter with the new __counted_by attribute. - Clarify do_unlinkat() cleanup so that it doesn't look like an extra iput() is done that would cause issues. - Simplify file cleanup when the file has never been opened. - Use module helper instead of open-coding it. - Predict error unlikely for stale retry. - Use WRITE_ONCE() for mount expiry field instead of just commenting that one hopes the compiler doesn't get smart. Fixes: - Fix readahead on block devices. - Fix writeback when layztime is enabled and inodes whose timestamp is the only thing that changed reside on wb->b_dirty_time. This caused excessively large zombie memory cgroup when lazytime was enabled as such inodes weren't handled fast enough. - Convert BUG_ON() to WARN_ON_ONCE() in open_last_lookups()" * tag 'vfs-6.7.misc' of gitolite.kernel.org:pub/scm/linux/kernel/git/vfs/vfs: (26 commits) file, i915: fix file reference for mmap_singleton() vfs: Convert BUG_ON to WARN_ON_ONCE in open_last_lookups writeback, cgroup: switch inodes with dirty timestamps to release dying cgwbs chardev: Simplify usage of try_module_get() ovl: rely on SB_I_NOUMASK fs: fix umask on NFS with CONFIG_FS_POSIX_ACL=n fs: store real path instead of fake path in backing file f_path fs: create helper file_user_path() for user displayed mapped file path fs: get mnt_writers count for an open backing file's real path vfs: stop counting on gcc not messing with mnt_expiry_mark if not asked vfs: predict the error in retry_estale as unlikely backing file: free directly vfs: fix readahead(2) on block devices io_uring: use files_lookup_fd_locked() file: convert to SLAB_TYPESAFE_BY_RCU vfs: shave work on failed file open fs: simplify misleading code to remove ambiguity regarding ihold()/iput() watch_queue: Annotate struct watch_filter with __counted_by fs/pipe: use spinlock in pipe_read() only if there is a watch_queue fs/pipe: remove unnecessary spinlock from pipe_write() ...