switch generic_write_checks() to iocb and iter

... returning -E... upon error and amount of data left in iter after
(possible) truncation upon success.  Note, that normal case gives
a non-zero (positive) return value, so any tests for != 0 _must_ be
updated.

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

Conflicts:
	fs/ext4/file.c

1 files changed, 6 insertions, 14 deletions

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 42b1fa33a17a..c10785f10d1d 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -97,9 +97,7 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
         struct blk_plug plug;
         int o_direct = io_is_direct(file);
         int overwrite = 0;
-        size_t length = iov_iter_count(from);
         ssize_t ret;
-        loff_t pos;
 
         /*
          * Unaligned direct AIO must be serialized; see comment above
@@ -116,16 +114,10 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
         }
 
         mutex_lock(&inode->i_mutex);
-        ret = generic_write_checks(file, &iocb->ki_pos, &length);
-        if (ret)
+        ret = generic_write_checks(iocb, from);
+        if (ret <= 0)
                 goto out;
 
-        if (length == 0)
-                goto out;
-
-        iov_iter_truncate(from, length);
-        pos = iocb->ki_pos;
-
         /*
          * If we have encountered a bitmap-format file, the size limit
          * is smaller than s_maxbytes, which is for extent-mapped files.
@@ -133,19 +125,19 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
         if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) {
                 struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
 
-                if (pos >= sbi->s_bitmap_maxbytes) {
+                if (iocb->ki_pos >= sbi->s_bitmap_maxbytes) {
                         ret = -EFBIG;
                         goto out;
                 }
-                iov_iter_truncate(from, sbi->s_bitmap_maxbytes - pos);
+                iov_iter_truncate(from, sbi->s_bitmap_maxbytes - iocb->ki_pos);
         }
 
         iocb->private = &overwrite;
         if (o_direct) {
-                length = iov_iter_count(from);
+                size_t length = iov_iter_count(from);
+                loff_t pos = iocb->ki_pos;
                 blk_start_plug(&plug);
 
-
                 /* check whether we do a DIO overwrite or not */
                 if (ext4_should_dioread_nolock(inode) && !aio_mutex &&
                     !file->f_mapping->nrpages && pos + length <= i_size_read(inode)) {