fiemap: use kernel-doc includes in fiemap docbook

Add some kernel-doc notation to structs in fiemap header files
then pull that into Documentation/filesystems/fiemap.rst
instead of duplicating the header file structs in fiemap.rst.
This helps to future-proof fiemap.rst against struct changes.

Add missing flags documentation from header files into fiemap.rst
for FIEMAP_FLAG_CACHE and FIEMAP_EXTENT_SHARED.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20241121011352.201907-1-rdunlap@infradead.org
Cc: Christoph Hellwig <hch@lst.de>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

1 files changed, 15 insertions, 34 deletions

diff --git a/Documentation/filesystems/fiemap.rst b/Documentation/filesystems/fiemap.rst
index 93fc96f760aa..23b3ed229e49 100644
--- a/Documentation/filesystems/fiemap.rst
+++ b/Documentation/filesystems/fiemap.rst
@@ -12,21 +12,10 @@ returns a list of extents.
 Request Basics
 --------------
 
-A fiemap request is encoded within struct fiemap::
-
-  struct fiemap {
-	__u64	fm_start;	 /* logical offset (inclusive) at
-				  * which to start mapping (in) */
-	__u64	fm_length;	 /* logical length of mapping which
-				  * userspace cares about (in) */
-	__u32	fm_flags;	 /* FIEMAP_FLAG_* flags for request (in/out) */
-	__u32	fm_mapped_extents; /* number of extents that were
-				    * mapped (out) */
-	__u32	fm_extent_count; /* size of fm_extents array (in) */
-	__u32	fm_reserved;
-	struct fiemap_extent fm_extents[0]; /* array of mapped extents (out) */
-  };
+A fiemap request is encoded within struct fiemap:
 
+.. kernel-doc:: include/uapi/linux/fiemap.h
+   :identifiers: fiemap
 
 fm_start, and fm_length specify the logical range within the file
 which the process would like mappings for. Extents returned mirror
@@ -60,6 +49,8 @@ FIEMAP_FLAG_XATTR
   If this flag is set, the extents returned will describe the inodes
   extended attribute lookup tree, instead of its data tree.
 
+FIEMAP_FLAG_CACHE
+  This flag requests caching of the extents.
 
 Extent Mapping
 --------------
@@ -77,18 +68,10 @@ complete the requested range and will not have the FIEMAP_EXTENT_LAST
 flag set (see the next section on extent flags).
 
 Each extent is described by a single fiemap_extent structure as
-returned in fm_extents::
-
-    struct fiemap_extent {
-	    __u64	fe_logical;  /* logical offset in bytes for the start of
-				* the extent */
-	    __u64	fe_physical; /* physical offset in bytes for the start
-				* of the extent */
-	    __u64	fe_length;   /* length in bytes for the extent */
-	    __u64	fe_reserved64[2];
-	    __u32	fe_flags;    /* FIEMAP_EXTENT_* flags for this extent */
-	    __u32	fe_reserved[3];
-    };
+returned in fm_extents:
+
+.. kernel-doc:: include/uapi/linux/fiemap.h
+    :identifiers: fiemap_extent
 
 All offsets and lengths are in bytes and mirror those on disk.  It is valid
 for an extents logical offset to start before the request or its logical
@@ -175,6 +158,8 @@ FIEMAP_EXTENT_MERGED
   userspace would be highly inefficient, the kernel will try to merge most
   adjacent blocks into 'extents'.
 
+FIEMAP_EXTENT_SHARED
+  This flag is set to request that space be shared with other files.
 
 VFS -> File System Implementation
 ---------------------------------
@@ -191,14 +176,10 @@ each discovered extent::
                      u64 len);
 
 ->fiemap is passed struct fiemap_extent_info which describes the
-fiemap request::
-
-  struct fiemap_extent_info {
-	unsigned int fi_flags;		/* Flags as passed from user */
-	unsigned int fi_extents_mapped;	/* Number of mapped extents */
-	unsigned int fi_extents_max;	/* Size of fiemap_extent array */
-	struct fiemap_extent *fi_extents_start;	/* Start of fiemap_extent array */
-  };
+fiemap request:
+
+.. kernel-doc:: include/linux/fiemap.h
+    :identifiers: fiemap_extent_info
 
 It is intended that the file system should not need to access any of this
 structure directly. Filesystem handlers should be tolerant to signals and return