Merge tag 'vfs-7.0-rc1.misc.2' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

Pull more misc vfs updates from Christian Brauner:
 "Features:

   - Optimize close_range() from O(range size) to O(active FDs) by using
     find_next_bit() on the open_fds bitmap instead of linearly scanning
     the entire requested range. This is a significant improvement for
     large-range close operations on sparse file descriptor tables.

   - Add FS_XFLAG_VERITY file attribute for fs-verity files, retrievable
     via FS_IOC_FSGETXATTR and file_getattr(). The flag is read-only.
     Add tracepoints for fs-verity enable and verify operations,
     replacing the previously removed debug printk's.

   - Prevent nfsd from exporting special kernel filesystems like pidfs
     and nsfs. These filesystems have custom ->open() and ->permission()
     export methods that are designed for open_by_handle_at(2) only and
     are incompatible with nfsd. Update the exportfs documentation
     accordingly.

  Fixes:

   - Fix KMSAN uninit-value in ovl_fill_real() where strcmp() was used
     on a non-null-terminated decrypted directory entry name from
     fscrypt. This triggered on encrypted lower layers when the
     decrypted name buffer contained uninitialized tail data.

     The fix also adds VFS-level name_is_dot(), name_is_dotdot(), and
     name_is_dot_dotdot() helpers, replacing various open-coded "." and
     ".." checks across the tree.

   - Fix read-only fsflags not being reset together with xflags in
     vfs_fileattr_set(). Currently harmless since no read-only xflags
     overlap with flags, but this would cause inconsistencies for any
     future shared read-only flag

   - Return -EREMOTE instead of -ESRCH from PIDFD_GET_INFO when the
     target process is in a different pid namespace. This lets userspace
     distinguish "process exited" from "process in another namespace",
     matching glibc's pidfd_getpid() behavior

  Cleanups:

   - Use C-string literals in the Rust seq_file bindings, replacing the
     kernel::c_str!() macro (available since Rust 1.77)

   - Fix typo in d_walk_ret enum comment, add porting notes for the
     readlink_copy() calling convention change"

* tag 'vfs-7.0-rc1.misc.2' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
  fs: add porting notes about readlink_copy()
  pidfs: return -EREMOTE when PIDFD_GET_INFO is called on another ns
  nfsd: do not allow exporting of special kernel filesystems
  exportfs: clarify the documentation of open()/permission() expotrfs ops
  fsverity: add tracepoints
  fs: add FS_XFLAG_VERITY for fs-verity files
  rust: seq_file: replace `kernel::c_str!` with C-Strings
  fs: dcache: fix typo in enum d_walk_ret comment
  ovl: use name_is_dot* helpers in readdir code
  fs: add helpers name_is_dot{,dot,_dotdot}
  ovl: Fix uninit-value in ovl_fill_real
  fs: reset read-only fsflags together with xflags
  fs/file: optimize close_range() complexity from O(N) to O(Sparse)

2 files changed, 26 insertions, 0 deletions

diff --git a/Documentation/filesystems/fsverity.rst b/Documentation/filesystems/fsverity.rst
index 412cf11e3298..22b49b295d1f 100644
--- a/Documentation/filesystems/fsverity.rst
+++ b/Documentation/filesystems/fsverity.rst
@@ -341,6 +341,22 @@ the file has fs-verity enabled.  This can perform better than
 FS_IOC_GETFLAGS and FS_IOC_MEASURE_VERITY because it doesn't require
 opening the file, and opening verity files can be expensive.
 
+FS_IOC_FSGETXATTR
+-----------------
+
+Since Linux v7.0, the FS_IOC_FSGETXATTR ioctl sets FS_XFLAG_VERITY (0x00020000)
+in the returned flags when the file has verity enabled. Note that this attribute
+cannot be set with FS_IOC_FSSETXATTR as enabling verity requires input
+parameters. See FS_IOC_ENABLE_VERITY.
+
+file_getattr
+------------
+
+Since Linux v7.0, the file_getattr() syscall sets FS_XFLAG_VERITY (0x00020000)
+in the returned flags when the file has verity enabled. Note that this attribute
+cannot be set with file_setattr() as enabling verity requires input parameters.
+See FS_IOC_ENABLE_VERITY.
+
 .. _accessing_verity_files:
 
 Accessing verity files
diff --git a/Documentation/filesystems/porting.rst b/Documentation/filesystems/porting.rst
index 79e2c3008289..52ff1d19405b 100644
--- a/Documentation/filesystems/porting.rst
+++ b/Documentation/filesystems/porting.rst
@@ -1351,3 +1351,13 @@ and do_rmdir()) are gone; they are replaced with non-consuming analogues
 (filename_renameat2(), etc.)
 Callers are adjusted - responsibility for dropping the filenames belongs
 to them now.
+
+---
+
+**mandatory**
+
+readlink_copy() now requires link length as the 4th argument. Said length needs
+to match what strlen() would return if it was ran on the string.
+
+However, if the string is freely accessible for the duration of inode's
+lifetime, consider using inode_set_cached_link() instead.