btrfs-progs: docs: update file attributes

Note about inheritable flags, annotate to what the attributes apply.

[ci skip]

Signed-off-by: David Sterba <dsterba@suse.com>

Author: kdave

Documentation/ch-file-attributes.rst

@@ -12,16 +12,25 @@ that:
   no standard tool to change the bits, there's support in :manref:`xfs_io(8)` as
   command **xfs_io -c chattr**
 
+Attributes have constraints associated and not all combinations can be set, the
+order of setting them also matters. Most attributes apply to files and
+directories but the semantics may differ. For directories the attribute may
+only mean to set this attribute to all new files (*inheritable* in the list
+below). Some attributes need root privileges to be set.
+
 Attributes
 ^^^^^^^^^^
 
 a
+        (file, dir, root)
         *append only*, new writes are always written at the end of the file
 
 A
+        (file, dir)
         *no atime updates*
 
 c
+        (file, dir, inherited)
         *compress data*, all data written after this attribute is set will be compressed.
         Please note that compression is also affected by the mount options or the parent
         directory attributes.
@@ -30,6 +39,7 @@ c
         This attribute cannot be set with 'm' at the same time.
 
 C
+        (file, dir, inherited)
         *no copy-on-write*, file data modifications are done in-place
 
         When set on a directory, all newly created files will inherit this attribute.
@@ -39,18 +49,22 @@ C
                 empty files.
 
 d
+        (file)
         *no dump*, makes sense with 3rd party tools like :manref:`dump(8)`, on BTRFS the
         attribute can be set/unset but no other special handling is done
 
 D
+        (dir)
         *synchronous directory updates*, for more details search :manref:`open(2)` for *O_SYNC*
         and *O_DSYNC*
 
 i
+        (file, dir, root)
         *immutable*, no file data and metadata changes allowed even to the root user as
         long as this attribute is set (obviously the exception is unsetting the attribute)
 
 m
+        (file, dir)
         *no compression*, permanently turn off compression on the given file. Any
         compression mount options will not affect this file. (:manref:`chattr(1)` support added in
         1.46.2)
@@ -59,9 +73,14 @@ m
         This attribute cannot be set with *c* at the same time.
 
 S
+        (file)
         *synchronous updates*, for more details search :manref:`open(2)` for *O_SYNC* and
         *O_DSYNC*
 
+V
+        (file, read-only)
+        *fs-verity enabled* on the file
+
 No other attributes are supported.  For the complete list please refer to the
 :manref:`chattr(1)` manual page.