file_attr(2type)                                              file_attr(2type)

NAME
       file_attr - filesystem file attributes

SYNOPSIS
       #include <linux/fs.h>

       struct file_attr {
            u64  fa_xflags;      // Extended flags
            u32  fa_extsize;     // Extent size hint
            u32  fa_nextents;    // Number of extents (read-only)
            u32  fa_projid;      // Project identifier
            u32  fa_cowextsize;  // CoW extent size hint
       };

DESCRIPTION
       Describes filesystem file attributes for use with the file_getattr(2)
       and file_setattr(2) system calls.

       The fields are as follows:

       .fa_xflags
              This field contains file attribute flags.  It is a bit mask
              consisting of zero or more of the FS_XFLAG_* flags.  See Flags
              below for a list of flags.

       .fa_extsize
              Extent size allocator hint in bytes.  This value suggests a
              preferred extent size for new allocations to this file.

       .fa_nextents
              Number of data extents in the file (read-only).  This field is
              filled in by file_getattr(2) and is ignored by file_setattr(2).

       .fa_projid
              Project identifier.  Used by quota systems quotactl(2) to group
              related files.

       .fa_cowextsize
              Copy-on-Write (CoW) extent size hint in bytes.  This value
              suggests a preferred extent size for CoW operations.

   Flags

              FS_XFLAG_REALTIME
                     Data is stored in a realtime volume.

              FS_XFLAG_IMMUTABLE
                     File cannot be modified.

              FS_XFLAG_APPEND
                     All writes must append to the end of the file.

              FS_XFLAG_SYNC
                     All writes are synchronous.

              FS_XFLAG_NOATIME
                     Do not update file access time on reads.

              FS_XFLAG_NODUMP
                     Do not include file in backups.

              FS_XFLAG_DAX
                     Use Direct Access (DAX) for I/O operations.

              FS_XFLAG_NODEFRAG
                     Exclude this file from defragmentation operations.

              FS_XFLAG_FILESTREAM
                     Use filestream allocator for this file.

              FS_XFLAG_EXTSIZE
                     Use the extent size hint from the fa_extsize field.

              FS_XFLAG_COWEXTSIZE
                     Use the CoW extent size hint from the fa_cowextsize
                     field.

       Directory-only flags:

              FS_XFLAG_RTINHERIT
                     New files created in this directory inherit the realtime
                     flag.

              FS_XFLAG_NOSYMLINKS
                     Disallow creation of symbolic links in this directory.

              FS_XFLAG_EXTSZINHERIT
                     New files created in this directory inherit the extent
                     size hint.

              FS_XFLAG_PROJINHERIT
                     New files created in this directory inherit the project
                     identifier.

       Read-only flags:

              FS_XFLAG_PREALLOC
                     File has preallocated extents.

              FS_XFLAG_HASATTR
                     File has extended attributes.

              FS_XFLAG_VERITY
                     File has fs-verity enabled.

              FS_XFLAG_CASEFOLD
                     The filesystem performs case-insensitive lookups (file
                     and directory name comparisons ignore case).

              FS_XFLAG_CASENONPRESERVING
                     The filesystem does not preserve the case of file and
                     directory names.

       Not all filesystems support all flags.  Setting unsupported flags may
       result in an error.

HISTORY
   Linux v6.17
       This structure is introduced.

   Linux v7.2
       The FS_XFLAG_CASEFOLD and FS_XFLAG_CASENONPRESERVING are introduced to
       enable upper layers, such as NFSD, to retrieve case sensitivity
       information.

SEE ALSO
       file_getattr(2), file_setattr(2)

Linux man-pages 6.20              2026-10-11                  file_attr(2type)