linux/fs/ext3/fsync.c
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   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/blkdev.h>
  27#include <linux/fs.h>
  28#include <linux/sched.h>
  29#include <linux/writeback.h>
  30#include <linux/jbd.h>
  31#include <linux/ext3_fs.h>
  32#include <linux/ext3_jbd.h>
  33
  34/*
  35 * akpm: A new design for ext3_sync_file().
  36 *
  37 * This is only called from sys_fsync(), sys_fdatasync() and sys_msync().
  38 * There cannot be a transaction open by this task.
  39 * Another task could have dirtied this inode.  Its data can be in any
  40 * state in the journalling system.
  41 *
  42 * What we do is just kick off a commit and wait on it.  This will snapshot the
  43 * inode to disk.
  44 */
  45
  46int ext3_sync_file(struct file *file, int datasync)
  47{
  48        struct inode *inode = file->f_mapping->host;
  49        struct ext3_inode_info *ei = EXT3_I(inode);
  50        journal_t *journal = EXT3_SB(inode->i_sb)->s_journal;
  51        int ret, needs_barrier = 0;
  52        tid_t commit_tid;
  53
  54        if (inode->i_sb->s_flags & MS_RDONLY)
  55                return 0;
  56
  57        J_ASSERT(ext3_journal_current_handle() == NULL);
  58
  59        /*
  60         * data=writeback,ordered:
  61         *  The caller's filemap_fdatawrite()/wait will sync the data.
  62         *  Metadata is in the journal, we wait for a proper transaction
  63         *  to commit here.
  64         *
  65         * data=journal:
  66         *  filemap_fdatawrite won't do anything (the buffers are clean).
  67         *  ext3_force_commit will write the file data into the journal and
  68         *  will wait on that.
  69         *  filemap_fdatawait() will encounter a ton of newly-dirtied pages
  70         *  (they were dirtied by commit).  But that's OK - the blocks are
  71         *  safe in-journal, which is all fsync() needs to ensure.
  72         */
  73        if (ext3_should_journal_data(inode))
  74                return ext3_force_commit(inode->i_sb);
  75
  76        if (datasync)
  77                commit_tid = atomic_read(&ei->i_datasync_tid);
  78        else
  79                commit_tid = atomic_read(&ei->i_sync_tid);
  80
  81        if (test_opt(inode->i_sb, BARRIER) &&
  82            !journal_trans_will_send_data_barrier(journal, commit_tid))
  83                needs_barrier = 1;
  84        log_start_commit(journal, commit_tid);
  85        ret = log_wait_commit(journal, commit_tid);
  86
  87        /*
  88         * In case we didn't commit a transaction, we have to flush
  89         * disk caches manually so that data really is on persistent
  90         * storage
  91         */
  92        if (needs_barrier)
  93                blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
  94        return ret;
  95}
  96