Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6:
  truncate: use new helpers
  truncate: new helpers
  fs: fix overflow in sys_mount() for in-kernel calls
  fs: Make unload_nls() NULL pointer safe
  freeze_bdev: grab active reference to frozen superblocks
  freeze_bdev: kill bd_mount_sem
  exofs: remove BKL from super operations
  fs/romfs: correct error-handling code
  vfs: seq_file: add helpers for data filling
  vfs: remove redundant position check in do_sendfile
  vfs: change sb->s_maxbytes to a loff_t
  vfs: explicitly cast s_maxbytes in fiemap_check_ranges
  libfs: return error code on failed attr set
  seq_file: return a negative error code when seq_path_root() fails.
  vfs: optimize touch_time() too
  vfs: optimization for touch_atime()
  vfs: split generic_forget_inode() so that hugetlbfs does not have to copy it
  fs/inode.c: add dev-id and inode number for debugging in init_special_inode()
  libfs: make simple_read_from_buffer conventional

1 files changed, 44 insertions, 2 deletions

diff --git a/fs/attr.c b/fs/attr.c
index 9fe1b1bd30a8..96d394bdaddf 100644
--- a/fs/attr.c
+++ b/fs/attr.c
@@ -18,7 +18,7 @@
 /* Taken over from the old code... */
 
 /* POSIX UID/GID verification for setting inode attributes. */
-int inode_change_ok(struct inode *inode, struct iattr *attr)
+int inode_change_ok(const struct inode *inode, struct iattr *attr)
 {
         int retval = -EPERM;
         unsigned int ia_valid = attr->ia_valid;
@@ -60,9 +60,51 @@ fine:
 error:
         return retval;
 }
-
 EXPORT_SYMBOL(inode_change_ok);
 
+/**
+ * inode_newsize_ok - may this inode be truncated to a given size
+ * @inode:      the inode to be truncated
+ * @offset:     the new size to assign to the inode
+ * @Returns:    0 on success, -ve errno on failure
+ *
+ * inode_newsize_ok will check filesystem limits and ulimits to check that the
+ * new inode size is within limits. inode_newsize_ok will also send SIGXFSZ
+ * when necessary. Caller must not proceed with inode size change if failure is
+ * returned. @inode must be a file (not directory), with appropriate
+ * permissions to allow truncate (inode_newsize_ok does NOT check these
+ * conditions).
+ *
+ * inode_newsize_ok must be called with i_mutex held.
+ */
+int inode_newsize_ok(const struct inode *inode, loff_t offset)
+{
+        if (inode->i_size < offset) {
+                unsigned long limit;
+
+                limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
+                if (limit != RLIM_INFINITY && offset > limit)
+                        goto out_sig;
+                if (offset > inode->i_sb->s_maxbytes)
+                        goto out_big;
+        } else {
+                /*
+                 * truncation of in-use swapfiles is disallowed - it would
+                 * cause subsequent swapout to scribble on the now-freed
+                 * blocks.
+                 */
+                if (IS_SWAPFILE(inode))
+                        return -ETXTBSY;
+        }
+
+        return 0;
+out_sig:
+        send_sig(SIGXFSZ, current, 0);
+out_big:
+        return -EFBIG;
+}
+EXPORT_SYMBOL(inode_newsize_ok);
+
 int inode_setattr(struct inode * inode, struct iattr * attr)
 {
         unsigned int ia_valid = attr->ia_valid;