LXR linux/fs/ext3/fsync.c

   1/*
   2 *  linux/fs/ext3/fsync.c
   3 *
   4 *  Copyright (C) 1993  Stephen Tweedie (sct@redhat.com)
   5 *  from
   6 *  Copyright (C) 1992  Remy Card (card@masi.ibp.fr)
   7 *                      Laboratoire MASI - Institut Blaise Pascal
   8 *                      Universite Pierre et Marie Curie (Paris VI)
   9 *  from
  10 *  linux/fs/minix/truncate.c   Copyright (C) 1991, 1992  Linus Torvalds
  11 *
  12 *  ext3fs fsync primitive
  13 *
  14 *  Big-endian to little-endian byte-swapping/bitmaps by
  15 *        David S. Miller (davem@caip.rutgers.edu), 1995
  16 *
  17 *  Removed unnecessary code duplication for little endian machines
  18 *  and excessive __inline__s.
  19 *        Andi Kleen, 1997
  20 *
  21 * Major simplications and cleanup - we only need to do the metadata, because
  22 * we can depend on generic_block_fdatasync() to sync the data blocks.
  23 */
  24
  25#include <linux/time.h>
  26#include <linux/fs.h>
  27#include <linux/sched.h>
  28#include <linux/writeback.h>
  29#include <linux/jbd.h>
  30#include <linux/ext3_fs.h>
  31#include <linux/ext3_jbd.h>
  32
  33/*
  34 * akpm: A new design for ext3_sync_file().
  35 *
  36 * This is only called from sys_fsync(), sys_fdatasync() and sys_msync().
  37 * There cannot be a transaction open by this task.
  38 * Another task could have dirtied this inode.  Its data can be in any
  39 * state in the journalling system.
  40 *
  41 * What we do is just kick off a commit and wait on it.  This will snapshot the
  42 * inode to disk.
  43 */
  44
  45int ext3_sync_file(struct file * file, struct dentry *dentry, int datasync)
  46{
  47        struct inode *inode = dentry->d_inode;
  48        int ret = 0;
  49
  50        J_ASSERT(ext3_journal_current_handle() == NULL);
  51
  52        /*
  53         * data=writeback:
  54         *  The caller's filemap_fdatawrite()/wait will sync the data.
  55         *  sync_inode() will sync the metadata
  56         *
  57         * data=ordered:
  58         *  The caller's filemap_fdatawrite() will write the data and
  59         *  sync_inode() will write the inode if it is dirty.  Then the caller's
  60         *  filemap_fdatawait() will wait on the pages.
  61         *
  62         * data=journal:
  63         *  filemap_fdatawrite won't do anything (the buffers are clean).
  64         *  ext3_force_commit will write the file data into the journal and
  65         *  will wait on that.
  66         *  filemap_fdatawait() will encounter a ton of newly-dirtied pages
  67         *  (they were dirtied by commit).  But that's OK - the blocks are
  68         *  safe in-journal, which is all fsync() needs to ensure.
  69         */
  70        if (ext3_should_journal_data(inode)) {
  71                ret = ext3_force_commit(inode->i_sb);
  72                goto out;
  73        }
  74
  75        if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
  76                goto out;
  77
  78        /*
  79         * The VFS has written the file data.  If the inode is unaltered
  80         * then we need not start a commit.
  81         */
  82        if (inode->i_state & (I_DIRTY_SYNC|I_DIRTY_DATASYNC)) {
  83                struct writeback_control wbc = {
  84                        .sync_mode = WB_SYNC_ALL,
  85                        .nr_to_write = 0, /* sys_fsync did this */
  86                };
  87                ret = sync_inode(inode, &wbc);
  88        }
  89out:
  90        return ret;
  91}
  92