From: Eric Sandeen <sandeen@redhat.com>

ext4 needs to deal with 2 different max file offsets for block- and
extent-allocated file formats, whereas the s_maxbytes scheme can only deal
with one.  So, for block-allocated files, we must catch and fix up
too-large offsets from within the filesystem.

Having iov_shorten exported allows such things as:

		if (pos + length > sbi->s_bitmap_maxbytes) {
			nr_segs = iov_shorten((struct iovec *)iov, nr_segs,
					      sbi->s_bitmap_maxbytes - pos);
		}

to fix up too-large writes to these files in ext4_file_write().

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Cc: Mingming Cao <cmm@us.ibm.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/read_write.c |    1 +
 1 file changed, 1 insertion(+)

diff -puN fs/read_write.c~export-iov_shorten-for-ext4s-use fs/read_write.c
--- a/fs/read_write.c~export-iov_shorten-for-ext4s-use
+++ a/fs/read_write.c
@@ -446,6 +446,7 @@ unsigned long iov_shorten(struct iovec *
 	}
 	return seg;
 }
+EXPORT_SYMBOL(iov_shorten)
 
 ssize_t do_sync_readv_writev(struct file *filp, const struct iovec *iov,
 		unsigned long nr_segs, size_t len, loff_t *ppos, iov_fn_t fn)
_