xfs: simplify xfs_attr_sf_findname

xfs_attr_sf_findname has the simple job of finding a xfs_attr_sf_entry in
the attr fork, but the convoluted calling convention obfuscates that.

Return the found entry as the return value instead of an pointer
argument, as the -ENOATTR/-EEXIST can be trivally derived from that, and
remove the basep argument, as it is equivalent of the offset of sfe in
the data for if an sfe was found, or an offset of totsize if not was
found.  To simplify the totsize computation add a xfs_attr_sf_endptr
helper that returns the imaginative xfs_attr_sf_entry at the end of
the current attrs.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

fs/xfs/libxfs/xfs_attr.c

@@ -862,8 +862,11 @@ xfs_attr_lookup(
 	if (!xfs_inode_hasattr(dp))
 		return -ENOATTR;
 
-	if (dp->i_af.if_format == XFS_DINODE_FMT_LOCAL)
-		return xfs_attr_sf_findname(args, NULL, NULL);
+	if (dp->i_af.if_format == XFS_DINODE_FMT_LOCAL) {
+		if (xfs_attr_sf_findname(args))
+			return -EEXIST;
+		return -ENOATTR;
+	}
 
 	if (xfs_attr_is_leaf(dp)) {
 		error = xfs_attr_leaf_hasname(args, &bp);

fs/xfs/libxfs/xfs_attr_leaf.c

@@ -698,47 +698,24 @@ xfs_attr_shortform_create(
 }
 
 /*
- * Return -EEXIST if attr is found, or -ENOATTR if not
- * args:  args containing attribute name and namelen
- * sfep:  If not null, pointer will be set to the last attr entry found on
-	  -EEXIST.  On -ENOATTR pointer is left at the last entry in the list
- * basep: If not null, pointer is set to the byte offset of the entry in the
- *	  list on -EEXIST.  On -ENOATTR, pointer is left at the byte offset of
- *	  the last entry in the list
+ * Return the entry if the attr in args is found, or NULL if not.
  */
-int
+struct xfs_attr_sf_entry *
 xfs_attr_sf_findname(
-	struct xfs_da_args	 *args,
-	struct xfs_attr_sf_entry **sfep,
-	unsigned int		 *basep)
+	struct xfs_da_args		*args)
 {
-	struct xfs_attr_shortform *sf = args->dp->i_af.if_data;
-	struct xfs_attr_sf_entry *sfe;
-	unsigned int		base = sizeof(struct xfs_attr_sf_hdr);
-	int			size = 0;
-	int			end;
-	int			i;
+	struct xfs_attr_shortform	*sf = args->dp->i_af.if_data;
+	struct xfs_attr_sf_entry	*sfe;
 
-	sfe = &sf->list[0];
-	end = sf->hdr.count;
-	for (i = 0; i < end; sfe = xfs_attr_sf_nextentry(sfe),
-			     base += size, i++) {
-		size = xfs_attr_sf_entsize(sfe);
-		if (!xfs_attr_match(args, sfe->namelen, sfe->nameval,
-				    sfe->flags))
-			continue;
-		break;
+	for (sfe = &sf->list[0];
+	     sfe < xfs_attr_sf_endptr(sf);
+	     sfe = xfs_attr_sf_nextentry(sfe)) {
+		if (xfs_attr_match(args, sfe->namelen, sfe->nameval,
+				sfe->flags))
+			return sfe;
 	}
 
-	if (sfep != NULL)
-		*sfep = sfe;
-
-	if (basep != NULL)
-		*basep = base;
-
-	if (i == end)
-		return -ENOATTR;
-	return -EEXIST;
+	return NULL;
 }
 
 /*
@@ -755,21 +732,19 @@ xfs_attr_shortform_add(
 	struct xfs_ifork		*ifp = &dp->i_af;
 	struct xfs_attr_shortform	*sf = ifp->if_data;
 	struct xfs_attr_sf_entry	*sfe;
-	int				offset, size;
+	int				size;
 
 	trace_xfs_attr_sf_add(args);
 
 	dp->i_forkoff = forkoff;
 
 	ASSERT(ifp->if_format == XFS_DINODE_FMT_LOCAL);
-	if (xfs_attr_sf_findname(args, &sfe, NULL) == -EEXIST)
-		ASSERT(0);
+	ASSERT(!xfs_attr_sf_findname(args));
 
-	offset = (char *)sfe - (char *)sf;
 	size = xfs_attr_sf_entsize_byname(args->namelen, args->valuelen);
 	sf = xfs_idata_realloc(dp, size, XFS_ATTR_FORK);
-	sfe = (struct xfs_attr_sf_entry *)((char *)sf + offset);
 
+	sfe = xfs_attr_sf_endptr(sf);
 	sfe->namelen = args->namelen;
 	sfe->valuelen = args->valuelen;
 	sfe->flags = args->attr_filter;
@@ -809,39 +784,38 @@ xfs_attr_sf_removename(
 	struct xfs_mount		*mp = dp->i_mount;
 	struct xfs_attr_shortform	*sf = dp->i_af.if_data;
 	struct xfs_attr_sf_entry	*sfe;
-	int				size = 0, end, totsize;
-	unsigned int			base;
-	int				error;
+	uint16_t			totsize = be16_to_cpu(sf->hdr.totsize);
+	void				*next, *end;
+	int				size = 0;
 
 	trace_xfs_attr_sf_remove(args);
 
-	error = xfs_attr_sf_findname(args, &sfe, &base);
-
-	/*
-	 * If we are recovering an operation, finding nothing to
-	 * remove is not an error - it just means there was nothing
-	 * to clean up.
-	 */
-	if (error == -ENOATTR && (args->op_flags & XFS_DA_OP_RECOVERY))
-		return 0;
-	if (error != -EEXIST)
-		return error;
-	size = xfs_attr_sf_entsize(sfe);
+	sfe = xfs_attr_sf_findname(args);
+	if (!sfe) {
+		/*
+		 * If we are recovering an operation, finding nothing to remove
+		 * is not an error, it just means there was nothing to clean up.
+		 */
+		if (args->op_flags & XFS_DA_OP_RECOVERY)
+			return 0;
+		return -ENOATTR;
+	}
 
 	/*
 	 * Fix up the attribute fork data, covering the hole
 	 */
-	end = base + size;
-	totsize = be16_to_cpu(sf->hdr.totsize);
-	if (end != totsize)
-		memmove(&((char *)sf)[base], &((char *)sf)[end], totsize - end);
+	size = xfs_attr_sf_entsize(sfe);
+	next = xfs_attr_sf_nextentry(sfe);
+	end = xfs_attr_sf_endptr(sf);
+	if (next < end)
+		memmove(sfe, next, end - next);
 	sf->hdr.count--;
-	be16_add_cpu(&sf->hdr.totsize, -size);
+	totsize -= size;
+	sf->hdr.totsize = cpu_to_be16(totsize);
 
 	/*
 	 * Fix up the start offset of the attribute fork
 	 */
-	totsize -= size;
 	if (totsize == sizeof(xfs_attr_sf_hdr_t) && xfs_has_attr2(mp) &&
 	    (dp->i_df.if_format != XFS_DINODE_FMT_BTREE) &&
 	    !(args->op_flags & (XFS_DA_OP_ADDNAME | XFS_DA_OP_REPLACE))) {

fs/xfs/libxfs/xfs_attr_leaf.h

@@ -51,9 +51,7 @@ int	xfs_attr_shortform_lookup(struct xfs_da_args *args);
 int	xfs_attr_shortform_getvalue(struct xfs_da_args *args);
 int	xfs_attr_shortform_to_leaf(struct xfs_da_args *args);
 int	xfs_attr_sf_removename(struct xfs_da_args *args);
-int	xfs_attr_sf_findname(struct xfs_da_args *args,
-			     struct xfs_attr_sf_entry **sfep,
-			     unsigned int *basep);
+struct xfs_attr_sf_entry *xfs_attr_sf_findname(struct xfs_da_args *args);
 int	xfs_attr_shortform_allfit(struct xfs_buf *bp, struct xfs_inode *dp);
 int	xfs_attr_shortform_bytesfit(struct xfs_inode *dp, int bytes);
 xfs_failaddr_t xfs_attr_shortform_verify(struct xfs_attr_shortform *sfp,

fs/xfs/libxfs/xfs_attr_sf.h

@@ -48,4 +48,11 @@ xfs_attr_sf_nextentry(struct xfs_attr_sf_entry *sfep)
 	return (void *)sfep + xfs_attr_sf_entsize(sfep);
 }
 
+/* pointer to the space after the last entry, e.g. for adding a new one */
+static inline struct xfs_attr_sf_entry *
+xfs_attr_sf_endptr(struct xfs_attr_shortform *sf)
+{
+	return (void *)sf + be16_to_cpu(sf->hdr.totsize);
+}
+
 #endif	/* __XFS_ATTR_SF_H__ */