1 files changed, 13 insertions, 17 deletions

diff --git a/fs/file.c b/fs/file.c
index a11e59b5d602..655338effe9c 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -46,27 +46,23 @@ static void free_fdtable_rcu(struct rcu_head *rcu)
 #define BITBIT_NR(nr)	BITS_TO_LONGS(BITS_TO_LONGS(nr))
 #define BITBIT_SIZE(nr)	(BITBIT_NR(nr) * sizeof(long))
 
+#define fdt_words(fdt) ((fdt)->max_fds / BITS_PER_LONG) // words in ->open_fds
 /*
  * Copy 'count' fd bits from the old table to the new table and clear the extra
  * space if any.  This does not copy the file pointers.  Called with the files
  * spinlock held for write.
  */
-static void copy_fd_bitmaps(struct fdtable *nfdt, struct fdtable *ofdt,
-			    unsigned int count)
+static inline void copy_fd_bitmaps(struct fdtable *nfdt, struct fdtable *ofdt,
+			    unsigned int copy_words)
 {
-	unsigned int cpy, set;
-
-	cpy = count / BITS_PER_BYTE;
-	set = (nfdt->max_fds - count) / BITS_PER_BYTE;
-	memcpy(nfdt->open_fds, ofdt->open_fds, cpy);
-	memset((char *)nfdt->open_fds + cpy, 0, set);
-	memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy);
-	memset((char *)nfdt->close_on_exec + cpy, 0, set);
-
-	cpy = BITBIT_SIZE(count);
-	set = BITBIT_SIZE(nfdt->max_fds) - cpy;
-	memcpy(nfdt->full_fds_bits, ofdt->full_fds_bits, cpy);
-	memset((char *)nfdt->full_fds_bits + cpy, 0, set);
+	unsigned int nwords = fdt_words(nfdt);
+
+	bitmap_copy_and_extend(nfdt->open_fds, ofdt->open_fds,
+			copy_words * BITS_PER_LONG, nwords * BITS_PER_LONG);
+	bitmap_copy_and_extend(nfdt->close_on_exec, ofdt->close_on_exec,
+			copy_words * BITS_PER_LONG, nwords * BITS_PER_LONG);
+	bitmap_copy_and_extend(nfdt->full_fds_bits, ofdt->full_fds_bits,
+			copy_words, nwords);
 }
 
 /*
@@ -84,7 +80,7 @@ static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt)
 	memcpy(nfdt->fd, ofdt->fd, cpy);
 	memset((char *)nfdt->fd + cpy, 0, set);
 
-	copy_fd_bitmaps(nfdt, ofdt, ofdt->max_fds);
+	copy_fd_bitmaps(nfdt, ofdt, fdt_words(ofdt));
 }
 
 /*
@@ -379,7 +375,7 @@ struct files_struct *dup_fd(struct files_struct *oldf, unsigned int max_fds, int
 		open_files = sane_fdtable_size(old_fdt, max_fds);
 	}
 
-	copy_fd_bitmaps(new_fdt, old_fdt, open_files);
+	copy_fd_bitmaps(new_fdt, old_fdt, open_files / BITS_PER_LONG);
 
 	old_fds = old_fdt->fd;
 	new_fds = new_fdt->fd;