export iov_shorten for ext4's use

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().

This patch is currently living in the ext4 patch queue.

---

Index: linux-2.6.24-rc3/fs/read_write.c
===================================================================
@@ -451,6 +451,8 @@ 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)
 {

(And, take 2... follow the coding style on export declarations...)

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().

This patch is currently living in the ext4 patch queue.

---

Index: linux-2.6.24-rc3/fs/read_write.c
===================================================================
@@ -450,6 +450,7 @@ 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)