[XFS] convert xfs_getbmap to take formatter functions

Preliminary work to hook up fiemap, this allows us to pass in an
arbitrary formatter to copy extent data back to userspace.

The formatter takes info for 1 extent, a pointer to the user "thing*"
and a pointer to a "filled" variable to indicate whether a userspace
buffer did get filled in (for fiemap, hole "extents" are skipped).

I'm just using the getbmapx struct as a "common denominator" because
as far as I can see, it holds all info that any formatters will care
about.

("*thing" because fiemap doesn't pass the user pointer around, but rather
has a pointer to a fiemap info structure, and helpers associated with it)

Signed-off-by: Eric Sandeen <sandeen@sandeen.net>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Niv Sardi <xaiki@sgi.com>

fs/xfs/linux-2.6/xfs_ioctl.c

@@ -1249,44 +1249,68 @@ xfs_ioc_setxflags(
 	return -xfs_ioctl_setattr(ip, &fa, mask);
 }
 
+STATIC int
+xfs_getbmap_format(void **ap, struct getbmapx *bmv, int *full)
+{
+	struct getbmap __user	*base = *ap;
+
+	/* copy only getbmap portion (not getbmapx) */
+	if (copy_to_user(base, bmv, sizeof(struct getbmap)))
+		return XFS_ERROR(EFAULT);
+
+	*ap += sizeof(struct getbmap);
+	return 0;
+}
+
 STATIC int
 xfs_ioc_getbmap(
 	struct xfs_inode	*ip,
 	int			ioflags,
 	unsigned int		cmd,
 	void			__user *arg)
 {
-	struct getbmap		bm;
-	int			iflags;
+	struct getbmapx		bmx;
 	int			error;
 
-	if (copy_from_user(&bm, arg, sizeof(bm)))
+	if (copy_from_user(&bmx, arg, sizeof(struct getbmapx)))
 		return -XFS_ERROR(EFAULT);
 
-	if (bm.bmv_count < 2)
+	if (bmx.bmv_count < 2)
 		return -XFS_ERROR(EINVAL);
 
-	iflags = (cmd == XFS_IOC_GETBMAPA ? BMV_IF_ATTRFORK : 0);
+	bmx.bmv_iflags = (cmd == XFS_IOC_GETBMAPA ? BMV_IF_ATTRFORK : 0);
 	if (ioflags & IO_INVIS)
-		iflags |= BMV_IF_NO_DMAPI_READ;
+		bmx.bmv_iflags |= BMV_IF_NO_DMAPI_READ;
 
-	error = xfs_getbmap(ip, &bm, (struct getbmap __user *)arg+1, iflags);
+	error = xfs_getbmap(ip, &bmx, xfs_getbmap_format,
+			    (struct getbmap *)arg+1);
 	if (error)
 		return -error;
 
-	if (copy_to_user(arg, &bm, sizeof(bm)))
+	/* copy back header - only size of getbmap */
+	if (copy_to_user(arg, &bmx, sizeof(struct getbmap)))
 		return -XFS_ERROR(EFAULT);
 	return 0;
 }
 
+STATIC int
+xfs_getbmapx_format(void **ap, struct getbmapx *bmv, int *full)
+{
+	struct getbmapx __user	*base = *ap;
+
+	if (copy_to_user(base, bmv, sizeof(struct getbmapx)))
+		return XFS_ERROR(EFAULT);
+
+	*ap += sizeof(struct getbmapx);
+	return 0;
+}
+
 STATIC int
 xfs_ioc_getbmapx(
 	struct xfs_inode	*ip,
 	void			__user *arg)
 {
 	struct getbmapx		bmx;
-	struct getbmap		bm;
-	int			iflags;
 	int			error;
 
 	if (copy_from_user(&bmx, arg, sizeof(bmx)))
@@ -1295,26 +1319,16 @@ xfs_ioc_getbmapx(
 	if (bmx.bmv_count < 2)
 		return -XFS_ERROR(EINVAL);
 
-	/*
-	 * Map input getbmapx structure to a getbmap
-	 * structure for xfs_getbmap.
-	 */
-	GETBMAP_CONVERT(bmx, bm);
-
-	iflags = bmx.bmv_iflags;
-
-	if (iflags & (~BMV_IF_VALID))
+	if (bmx.bmv_iflags & (~BMV_IF_VALID))
 		return -XFS_ERROR(EINVAL);
 
-	iflags |= BMV_IF_EXTENDED;
-
-	error = xfs_getbmap(ip, &bm, (struct getbmapx __user *)arg+1, iflags);
+	error = xfs_getbmap(ip, &bmx, xfs_getbmapx_format,
+			    (struct getbmapx *)arg+1);
 	if (error)
 		return -error;
 
-	GETBMAP_CONVERT(bm, bmx);
-
-	if (copy_to_user(arg, &bmx, sizeof(bmx)))
+	/* copy back header */
+	if (copy_to_user(arg, &bmx, sizeof(struct getbmapx)))
 		return -XFS_ERROR(EFAULT);
 
 	return 0;

fs/xfs/xfs_bmap.c

@@ -5811,9 +5811,9 @@ xfs_bunmapi(
 STATIC int
 xfs_getbmapx_fix_eof_hole(
 	xfs_inode_t		*ip,		/* xfs incore inode pointer */
-	struct getbmap		*out,		/* output structure */
+	struct getbmapx		*out,		/* output structure */
 	int			prealloced,	/* this is a file with
-						* preallocated data space */
+						 * preallocated data space */
 	__int64_t		end,		/* last block requested */
 	xfs_fsblock_t		startblock)
 {
@@ -5839,14 +5839,18 @@ xfs_getbmapx_fix_eof_hole(
 }
 
 /*
- * Fcntl interface to xfs_bmapi.
+ * Get inode's extents as described in bmv, and format for output.
+ * Calls formatter to fill the user's buffer until all extents
+ * are mapped, until the passed-in bmv->bmv_count slots have
+ * been filled, or until the formatter short-circuits the loop,
+ * if it is tracking filled-in extents on its own.
  */
 int						/* error code */
 xfs_getbmap(
 	xfs_inode_t		*ip,
-	struct getbmap		*bmv,		/* user bmap structure */
-	void			__user *ap,	/* pointer to user's array */
-	int			interface)	/* interface flags */
+	struct getbmapx		*bmv,		/* user bmap structure */
+	xfs_bmap_format_t	formatter,	/* format to user */
+	void			*arg)		/* formatter arg */
 {
 	__int64_t		bmvend;		/* last block requested */
 	int			error;		/* return value */
@@ -5859,19 +5863,20 @@ xfs_getbmap(
 	int			nexleft;	/* # of user extents left */
 	int			subnex;		/* # of bmapi's can do */
 	int			nmap;		/* number of map entries */
-	struct getbmap		out;		/* output structure */
+	struct getbmapx		out;		/* output structure */
 	int			whichfork;	/* data or attr fork */
 	int			prealloced;	/* this is a file with
 						 * preallocated data space */
 	int			sh_unwritten;	/* true, if unwritten */
 						/* extents listed separately */
+	int			iflags;		/* interface flags */
 	int			bmapi_flags;	/* flags for xfs_bmapi */
-	__int32_t		oflags;		/* getbmapx bmv_oflags field */
 
 	mp = ip->i_mount;
+	iflags = bmv->bmv_iflags;
 
-	whichfork = interface & BMV_IF_ATTRFORK ? XFS_ATTR_FORK : XFS_DATA_FORK;
-	sh_unwritten = (interface & BMV_IF_PREALLOC) != 0;
+	whichfork = iflags & BMV_IF_ATTRFORK ? XFS_ATTR_FORK : XFS_DATA_FORK;
+	sh_unwritten = (iflags & BMV_IF_PREALLOC) != 0;
 
 	/*	If the BMV_IF_NO_DMAPI_READ interface bit specified, do not
 	 *	generate a DMAPI read event.  Otherwise, if the DM_EVENT_READ
@@ -5886,7 +5891,7 @@ xfs_getbmap(
 	 *	could misinterpret holes in a DMAPI file as true holes,
 	 *	when in fact they may represent offline user data.
 	 */
-	if ((interface & BMV_IF_NO_DMAPI_READ) == 0 &&
+	if ((iflags & BMV_IF_NO_DMAPI_READ) == 0 &&
 	    DM_EVENT_ENABLED(ip, DM_EVENT_READ) &&
 	    whichfork == XFS_DATA_FORK) {
 		error = XFS_SEND_DATA(mp, DM_EVENT_READ, ip, 0, 0, 0, NULL);
@@ -5993,52 +5998,35 @@ xfs_getbmap(
 		ASSERT(nmap <= subnex);
 
 		for (i = 0; i < nmap && nexleft && bmv->bmv_length; i++) {
-			nexleft--;
-			oflags = (map[i].br_state == XFS_EXT_UNWRITTEN) ?
+			out.bmv_oflags = (map[i].br_state == XFS_EXT_UNWRITTEN) ?
 					BMV_OF_PREALLOC : 0;
 			out.bmv_offset = XFS_FSB_TO_BB(mp, map[i].br_startoff);
 			out.bmv_length = XFS_FSB_TO_BB(mp, map[i].br_blockcount);
+			out.bmv_unused1 = out.bmv_unused2 = 0;
 			ASSERT(map[i].br_startblock != DELAYSTARTBLOCK);
                         if (map[i].br_startblock == HOLESTARTBLOCK &&
 			    whichfork == XFS_ATTR_FORK) {
 				/* came to the end of attribute fork */
 				goto unlock_and_return;
 			} else {
+				int full = 0;	/* user array is full */
+
 				if (!xfs_getbmapx_fix_eof_hole(ip, &out,
 							prealloced, bmvend,
 							map[i].br_startblock)) {
 					goto unlock_and_return;
 				}
 
-				/* return either getbmap/getbmapx structure. */
-				if (interface & BMV_IF_EXTENDED) {
-					struct	getbmapx	outx;
-
-					GETBMAP_CONVERT(out,outx);
-					outx.bmv_oflags = oflags;
-					outx.bmv_unused1 = outx.bmv_unused2 = 0;
-					if (copy_to_user(ap, &outx,
-							sizeof(outx))) {
-						error = XFS_ERROR(EFAULT);
-						goto unlock_and_return;
-					}
-				} else {
-					if (copy_to_user(ap, &out,
-							sizeof(out))) {
-						error = XFS_ERROR(EFAULT);
-						goto unlock_and_return;
-					}
-				}
+				/* format results & advance arg */
+				error = formatter(&arg, &out, &full);
+				if (error || full)
+					goto unlock_and_return;
+				nexleft--;
 				bmv->bmv_offset =
 					out.bmv_offset + out.bmv_length;
 				bmv->bmv_length = MAX((__int64_t)0,
 					(__int64_t)(bmvend - bmv->bmv_offset));
 				bmv->bmv_entries++;
-				ap = (interface & BMV_IF_EXTENDED) ?
-						(void __user *)
-					((struct getbmapx __user *)ap + 1) :
-						(void __user *)
-					((struct getbmap __user *)ap + 1);
 			}
 		}
 	} while (nmap && nexleft && bmv->bmv_length);

fs/xfs/xfs_bmap.h

@@ -356,15 +356,18 @@ xfs_bmap_finish(
 	xfs_bmap_free_t		*flist,		/* i/o: list extents to free */
 	int			*committed);	/* xact committed or not */
 
+/* bmap to userspace formatter - copy to user & advance pointer */
+typedef int (*xfs_bmap_format_t)(void **, struct getbmapx *, int *);
+
 /*
- * Fcntl interface to xfs_bmapi.
+ * Get inode's extents as described in bmv, and format for output.
  */
 int						/* error code */
 xfs_getbmap(
 	xfs_inode_t		*ip,
-	struct getbmap		*bmv,		/* user bmap structure */
-	void			__user *ap,	/* pointer to user's array */
-	int			iflags);	/* interface flags */
+	struct getbmapx		*bmv,		/* user bmap structure */
+	xfs_bmap_format_t	formatter,	/* format to user */
+	void			*arg);		/* formatter arg */
 
 /*
  * Check if the endoff is outside the last extent. If so the caller will grow

fs/xfs/xfs_fs.h

@@ -114,22 +114,10 @@ struct getbmapx {
 #define BMV_IF_NO_DMAPI_READ	0x2	/* Do not generate DMAPI read event  */
 #define BMV_IF_PREALLOC		0x4	/* rtn status BMV_OF_PREALLOC if req */
 #define BMV_IF_VALID	(BMV_IF_ATTRFORK|BMV_IF_NO_DMAPI_READ|BMV_IF_PREALLOC)
-#ifdef __KERNEL__
-#define BMV_IF_EXTENDED 0x40000000	/* getpmapx if set */
-#endif
 
 /*	bmv_oflags values - returned for for each non-header segment */
 #define BMV_OF_PREALLOC		0x1	/* segment = unwritten pre-allocation */
 
-/*	Convert getbmap <-> getbmapx - move fields from p1 to p2. */
-#define GETBMAP_CONVERT(p1,p2) {	\
-	p2.bmv_offset = p1.bmv_offset;	\
-	p2.bmv_block = p1.bmv_block;	\
-	p2.bmv_length = p1.bmv_length;	\
-	p2.bmv_count = p1.bmv_count;	\
-	p2.bmv_entries = p1.bmv_entries;  }
-
-
 /*
  * Structure for XFS_IOC_FSSETDM.
  * For use by backup and restore programs to set the XFS on-disk inode