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Revision 7fb5409df092589b86cc9412d926879cb572b7f0 authored by Jan Kara on 10 February 2008, 06:08:38 UTC, committed by Theodore Ts'o on 10 February 2008, 06:08:38 UTC 
ext4: Fix Direct I/O locking
 
We cannot start transaction in ext4_direct_IO() and just let it last
during the whole write because dio_get_page() acquires mmap_sem which
ranks above transaction start (e.g. because we have dependency chain
mmap_sem->PageLock->journal_start, or because we update atime while
holding mmap_sem) and thus deadlocks could happen. We solve the problem
by starting a transaction separately for each ext4_get_block() call.

We *could* have a problem that we allocate a block and before its data
are written out the machine crashes and thus we expose stale data. But
that does not happen because for hole-filling generic code falls back to
buffered writes and for file extension, we add inode to orphan list and
thus in case of crash, journal replay will truncate inode back to the
original size.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
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Raw File
symlink.c 
/*
 * Symlink inode operations for Coda filesystem
 * Original version: (C) 1996 P. Braam and M. Callahan
 * Rewritten for Linux 2.1. (C) 1997 Carnegie Mellon University
 * 
 * Carnegie Mellon encourages users to contribute improvements to
 * the Coda project. Contact Peter Braam (coda@cs.cmu.edu).
 */

#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/time.h>
#include <linux/fs.h>
#include <linux/stat.h>
#include <linux/errno.h>
#include <linux/pagemap.h>
#include <linux/smp_lock.h>

#include <linux/coda.h>
#include <linux/coda_linux.h>
#include <linux/coda_psdev.h>
#include <linux/coda_fs_i.h>

static int coda_symlink_filler(struct file *file, struct page *page)
{
	struct inode *inode = page->mapping->host;
	int error;
	struct coda_inode_info *cii;
	unsigned int len = PAGE_SIZE;
	char *p = kmap(page);

	lock_kernel();
	cii = ITOC(inode);

	error = venus_readlink(inode->i_sb, &cii->c_fid, p, &len);
	unlock_kernel();
	if (error)
		goto fail;
	SetPageUptodate(page);
	kunmap(page);
	unlock_page(page);
	return 0;

fail:
	SetPageError(page);
	kunmap(page);
	unlock_page(page);
	return error;
}

const struct address_space_operations coda_symlink_aops = {
	.readpage	= coda_symlink_filler,
};
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