1 files changed, 45 insertions, 37 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index 5631d6b2a62d..3e49fe13d6ac 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1110,6 +1110,45 @@ success:
         return size;
 }
 
+/*
+ * Performs necessary checks before doing a write
+ * @iov:        io vector request
+ * @nr_segs:    number of segments in the iovec
+ * @count:      number of bytes to write
+ * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE
+ *
+ * Adjust number of segments and amount of bytes to write (nr_segs should be
+ * properly initialized first). Returns appropriate error code that caller
+ * should return or zero in case that write should be allowed.
+ */
+int generic_segment_checks(const struct iovec *iov,
+                        unsigned long *nr_segs, size_t *count, int access_flags)
+{
+        unsigned long   seg;
+        size_t cnt = 0;
+        for (seg = 0; seg < *nr_segs; seg++) {
+                const struct iovec *iv = &iov[seg];
+
+                /*
+                 * If any segment has a negative length, or the cumulative
+                 * length ever wraps negative then return -EINVAL.
+                 */
+                cnt += iv->iov_len;
+                if (unlikely((ssize_t)(cnt|iv->iov_len) < 0))
+                        return -EINVAL;
+                if (access_ok(access_flags, iv->iov_base, iv->iov_len))
+                        continue;
+                if (seg == 0)
+                        return -EFAULT;
+                *nr_segs = seg;
+                cnt -= iv->iov_len;     /* This segment is no good */
+                break;
+        }
+        *count = cnt;
+        return 0;
+}
+EXPORT_SYMBOL(generic_segment_checks);
+
 /**
  * generic_file_aio_read - generic filesystem read routine
  * @iocb:       kernel I/O control block
@@ -1131,24 +1170,9 @@ generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
         loff_t *ppos = &iocb->ki_pos;
 
         count = 0;
-        for (seg = 0; seg < nr_segs; seg++) {
-                const struct iovec *iv = &iov[seg];
-
-                /*
-                 * If any segment has a negative length, or the cumulative
-                 * length ever wraps negative then return -EINVAL.
-                 */
-                count += iv->iov_len;
-                if (unlikely((ssize_t)(count|iv->iov_len) < 0))
-                        return -EINVAL;
-                if (access_ok(VERIFY_WRITE, iv->iov_base, iv->iov_len))
-                        continue;
-                if (seg == 0)
-                        return -EFAULT;
-                nr_segs = seg;
-                count -= iv->iov_len;   /* This segment is no good */
-                break;
-        }
+        retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
+        if (retval)
+                return retval;
 
         /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
         if (filp->f_flags & O_DIRECT) {
@@ -2218,30 +2242,14 @@ __generic_file_aio_write_nolock(struct kiocb *iocb, const struct iovec *iov,
         size_t ocount;          /* original count */
         size_t count;           /* after file limit checks */
         struct inode    *inode = mapping->host;
-        unsigned long   seg;
         loff_t          pos;
         ssize_t         written;
         ssize_t         err;
 
         ocount = 0;
-        for (seg = 0; seg < nr_segs; seg++) {
-                const struct iovec *iv = &iov[seg];
-
-                /*
-                 * If any segment has a negative length, or the cumulative
-                 * length ever wraps negative then return -EINVAL.
-                 */
-                ocount += iv->iov_len;
-                if (unlikely((ssize_t)(ocount|iv->iov_len) < 0))
-                        return -EINVAL;
-                if (access_ok(VERIFY_READ, iv->iov_base, iv->iov_len))
-                        continue;
-                if (seg == 0)
-                        return -EFAULT;
-                nr_segs = seg;
-                ocount -= iv->iov_len;  /* This segment is no good */
-                break;
-        }
+        err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
+        if (err)
+                return err;
 
         count = ocount;
         pos = *ppos;