Merge tag 'vfs-7.2-rc1.casefold' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

Pull vfs casefolding updates from Christian Brauner:
 "This exposes the case folding behavior of local filesystems so that
  file servers - nfsd, ksmbd, and user space file servers - can report
  the actual behavior to clients instead of guessing.

  Filesystems report case-insensitive and case-nonpreserving behavior
  via new file_kattr flags in their fileattr_get implementations. fat,
  exfat, ntfs3, hfs, hfsplus, xfs, cifs, nfs, vboxsf, and isofs are
  wired up. Local filesystems that are not explicitly handled default to
  the usual POSIX behavior of case-sensitive and case-preserving.

  nfsd uses this to report case folding via NFSv3 PATHCONF and to
  implement the NFSv4 FATTR4_CASE_INSENSITIVE and FATTR4_CASE_PRESERVING
  attributes - both have been part of the NFS protocols for decades to
  support clients on non-POSIX systems - and ksmbd reports it via
  FS_ATTRIBUTE_INFORMATION. Exposing the information through the
  fileattr uapi covers user space file servers.

  The immediate motivation is interoperability: Windows NFS clients
  hard-require servers to report case-insensitivity for Win32
  applications to work correctly, and a client that knows the server is
  case-insensitive can avoid issuing multiple LOOKUP/READDIR requests
  searching for case variants.

  The Linux NFS client already grew support for case-insensitive shares
  years ago in support of the Hammerspace NFS server - negative dentry
  caching must be disabled (a lookup for "FILE.TXT" failing must not
  cache a negative entry when "file.txt" exists) and directory change
  invalidation must drop cached case-folded name variants. Such servers
  often operate in multi-protocol environments where a single file
  service instance caters to both NFS and SMB clients, and nfsd needs to
  report case folding properly to participate as a first-class citizen
  there.

  A follow-up series brings fixes for the initial work: the nfsd
  case-info probe now uses kernel credentials, maps -ESTALE to
  NFS3ERR_STALE, and has its cost capped across READDIR entries; the nfs
  client avoids transiently zeroed case capability bits during the probe
  and skips the pathconf probe when neither field is consumed; the
  FS_CASEFOLD_FL semantics are clarified in the UAPI header; and the
  tools UAPI headers are synced"

* tag 'vfs-7.2-rc1.casefold' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (22 commits)
  nfsd: Cap case-folding probe cost across READDIR entries
  nfsd: Map -ESTALE from case probe to NFS3ERR_STALE
  nfsd: Use kernel credentials for case-info probe
  fs: Clarify FS_CASEFOLD_FL semantics in UAPI header
  nfs: Skip pathconf probe when neither field is consumed
  nfs: Avoid transient zeroed case capability bits during probe
  tools headers UAPI: Sync case-sensitivity flags from linux/fs.h
  ksmbd: Report filesystem case sensitivity via FS_ATTRIBUTE_INFORMATION
  nfsd: Implement NFSv4 FATTR4_CASE_INSENSITIVE and FATTR4_CASE_PRESERVING
  nfsd: Report export case-folding via NFSv3 PATHCONF
  isofs: Implement fileattr_get for case sensitivity
  vboxsf: Implement fileattr_get for case sensitivity
  nfs: Implement fileattr_get for case sensitivity
  cifs: Implement fileattr_get for case sensitivity
  xfs: Report case sensitivity in fileattr_get
  hfsplus: Report case sensitivity in fileattr_get
  hfs: Implement fileattr_get for case sensitivity
  ntfs3: Implement fileattr_get for case sensitivity
  exfat: Implement fileattr_get for case sensitivity
  fat: Implement fileattr_get for case sensitivity
  ...

1 files changed, 17 insertions, 1 deletions

diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
index 13f71202845e..bd87262f2e34 100644
--- a/include/uapi/linux/fs.h
+++ b/include/uapi/linux/fs.h
@@ -254,6 +254,13 @@ struct file_attr {
 #define FS_XFLAG_DAX		0x00008000	/* use DAX for IO */
 #define FS_XFLAG_COWEXTSIZE	0x00010000	/* CoW extent size allocator hint */
 #define FS_XFLAG_VERITY		0x00020000	/* fs-verity enabled */
+/*
+ * Case handling flags (read-only, cannot be set via ioctl).
+ * Default (neither set) indicates POSIX semantics: case-sensitive
+ * lookups and case-preserving storage.
+ */
+#define FS_XFLAG_CASEFOLD	0x00040000	/* case-insensitive lookups */
+#define FS_XFLAG_CASENONPRESERVING 0x00080000	/* case not preserved */
 #define FS_XFLAG_HASATTR	0x80000000	/* no DIFLAG for this	*/
 
 /* the read-only stuff doesn't really belong here, but any other place is
@@ -388,7 +395,16 @@ struct file_attr {
 #define FS_DAX_FL			0x02000000 /* Inode is DAX */
 #define FS_INLINE_DATA_FL		0x10000000 /* Reserved for ext4 */
 #define FS_PROJINHERIT_FL		0x20000000 /* Create with parents projid */
-#define FS_CASEFOLD_FL			0x40000000 /* Folder is case insensitive */
+/*
+ * FS_CASEFOLD_FL indicates case-insensitive name lookup. The
+ * bit is most often reported on directories, where it controls
+ * lookups of entries within. Filesystems that derive
+ * case-insensitivity from mount or volume state may also report
+ * it on non-directory inodes; userspace must not assume the bit
+ * is directory-only. FS_XFLAG_CASEFOLD reports the same
+ * information read-only via FS_IOC_FSGETXATTR.
+ */
+#define FS_CASEFOLD_FL			0x40000000
 #define FS_RESERVED_FL			0x80000000 /* reserved for ext2 lib */
 
 #define FS_FL_USER_VISIBLE		0x0003DFFF /* User visible flags */