Don't enforce NAME_MAX in fs.Dirent.walk().

Maximum filename length is filesystem-dependent, and obtained via
statfs::f_namelen. This limit is usually 255 bytes (NAME_MAX), but not
always. For example, VFAT supports filenames of up to 255... UCS-2
characters, which Linux conservatively takes to mean UTF-8-encoded
bytes: fs/fat/inode.c:fat_statfs(), FAT_LFN_LEN * NLS_MAX_CHARSET_SIZE.
As a result, Linux's VFS does not enforce NAME_MAX:

$ rg --maxdepth=1 '\WNAME_MAX\W' fs/ include/linux/
fs/libfs.c
38:     buf->f_namelen = NAME_MAX;
64:     if (dentry->d_name.len > NAME_MAX)

include/linux/relay.h
74:     char base_filename[NAME_MAX];   /* saved base filename */

include/linux/fscrypt.h
149: * filenames up to NAME_MAX bytes, since base64 encoding expands the length.

include/linux/exportfs.h
176: *    understanding that it is already pointing to a a %NAME_MAX+1 sized

Remove this check from core VFS, and add it to ramfs (and by extension
tmpfs), where it is actually applicable:
mm/shmem.c:shmem_dir_inode_operations.lookup == simple_lookup *does*
enforce NAME_MAX.

PiperOrigin-RevId: 245324748
Change-Id: I17567c4324bfd60e31746a5270096e75db963fac

0 files changed, 0 insertions, 0 deletions