convert ext4 to ->write_iter()

unfortunately, Ted's changes to ext4_file_write() are *still* an
incomplete fix - playing with rlimits can let you smuggle an
unaligned request past the checks.  So there almost certainly
will be more merge PITA around that place...

[fix from Peter Ujfalusi <peter.ujfalusi@ti.com> folded]

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 11 insertions, 18 deletions

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 86a13a514e4a..48383a5f37a1 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -74,26 +74,22 @@ void ext4_unwritten_wait(struct inode *inode)
  * or one thread will zero the other's data, causing corruption.
  */
 static int
-ext4_unaligned_aio(struct inode *inode, const struct iovec *iov,
-                   unsigned long nr_segs, loff_t pos)
+ext4_unaligned_aio(struct inode *inode, struct iov_iter *from, loff_t pos)
 {
         struct super_block *sb = inode->i_sb;
         int blockmask = sb->s_blocksize - 1;
-        size_t count = iov_length(iov, nr_segs);
-        loff_t final_size = pos + count;
 
         if (pos >= i_size_read(inode))
                 return 0;
 
-        if ((pos & blockmask) || (final_size & blockmask))
+        if ((pos | iov_iter_alignment(from)) & blockmask)
                 return 1;
 
         return 0;
 }
 
 static ssize_t
-ext4_file_write(struct kiocb *iocb, const struct iovec *iov,
-                unsigned long nr_segs, loff_t pos)
+ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 {
         struct file *file = iocb->ki_filp;
         struct inode *inode = file_inode(iocb->ki_filp);
@@ -101,10 +97,9 @@ ext4_file_write(struct kiocb *iocb, const struct iovec *iov,
         struct blk_plug plug;
         int o_direct = file->f_flags & O_DIRECT;
         int overwrite = 0;
-        size_t length = iov_length(iov, nr_segs);
+        size_t length = iov_iter_count(from);
         ssize_t ret;
-
-        BUG_ON(iocb->ki_pos != pos);
+        loff_t pos = iocb->ki_pos;
 
         /*
          * Unaligned direct AIO must be serialized; see comment above
@@ -114,7 +109,7 @@ ext4_file_write(struct kiocb *iocb, const struct iovec *iov,
             ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS) &&
             !is_sync_kiocb(iocb) &&
             (file->f_flags & O_APPEND ||
-             ext4_unaligned_aio(inode, iov, nr_segs, pos))) {
+             ext4_unaligned_aio(inode, from, pos))) {
                 aio_mutex = ext4_aio_mutex(inode);
                 mutex_lock(aio_mutex);
                 ext4_unwritten_wait(inode);
@@ -138,10 +133,8 @@ ext4_file_write(struct kiocb *iocb, const struct iovec *iov,
                         goto errout;
                 }
 
-                if (pos + length > sbi->s_bitmap_maxbytes) {
-                        nr_segs = iov_shorten((struct iovec *)iov, nr_segs,
-                                              sbi->s_bitmap_maxbytes - pos);
-                }
+                if (pos + length > sbi->s_bitmap_maxbytes)
+                        iov_iter_truncate(from, sbi->s_bitmap_maxbytes - pos);
         }
 
         if (o_direct) {
@@ -179,7 +172,7 @@ ext4_file_write(struct kiocb *iocb, const struct iovec *iov,
                 }
         }
 
-        ret = __generic_file_aio_write(iocb, iov, nr_segs);
+        ret = __generic_file_write_iter(iocb, from);
         mutex_unlock(&inode->i_mutex);
 
         if (ret > 0) {
@@ -594,9 +587,9 @@ loff_t ext4_llseek(struct file *file, loff_t offset, int whence)
 const struct file_operations ext4_file_operations = {
         .llseek         = ext4_llseek,
         .read           = new_sync_read,
-        .write          = do_sync_write,
+        .write          = new_sync_write,
         .read_iter      = generic_file_read_iter,
-        .aio_write      = ext4_file_write,
+        .write_iter     = ext4_file_write_iter,
         .unlocked_ioctl = ext4_ioctl,
 #ifdef CONFIG_COMPAT
         .compat_ioctl   = ext4_compat_ioctl,