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/blkdev.h>
  26#include <linux/writeback.h>
  27#include "ext3.h"
  28
  29/*
  30 * akpm: A new design for ext3_sync_file().
  31 *
  32 * This is only called from sys_fsync(), sys_fdatasync() and sys_msync().
  33 * There cannot be a transaction open by this task.
  34 * Another task could have dirtied this inode.  Its data can be in any
  35 * state in the journalling system.
  36 *
  37 * What we do is just kick off a commit and wait on it.  This will snapshot the
  38 * inode to disk.
  39 */
  40
  41int ext3_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
  42{
  43        struct inode *inode = file->f_mapping->host;
  44        struct ext3_inode_info *ei = EXT3_I(inode);
  45        journal_t *journal = EXT3_SB(inode->i_sb)->s_journal;
  46        int ret, needs_barrier = 0;
  47        tid_t commit_tid;
  48
  49        trace_ext3_sync_file_enter(file, datasync);
  50
  51        if (inode->i_sb->s_flags & MS_RDONLY)
  52                return 0;
  53
  54        ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
  55        if (ret)
  56                goto out;
  57
  58        J_ASSERT(ext3_journal_current_handle() == NULL);
  59
  60        /*
  61         * data=writeback,ordered:
  62         *  The caller's filemap_fdatawrite()/wait will sync the data.
  63         *  Metadata is in the journal, we wait for a proper transaction
  64         *  to commit here.
  65         *
  66         * data=journal:
  67         *  filemap_fdatawrite won't do anything (the buffers are clean).
  68         *  ext3_force_commit will write the file data into the journal and
  69         *  will wait on that.
  70         *  filemap_fdatawait() will encounter a ton of newly-dirtied pages
  71         *  (they were dirtied by commit).  But that's OK - the blocks are
  72         *  safe in-journal, which is all fsync() needs to ensure.
  73         */
  74        if (ext3_should_journal_data(inode)) {
  75                ret = ext3_force_commit(inode->i_sb);
  76                goto out;
  77        }
  78
  79        if (datasync)
  80                commit_tid = atomic_read(&ei->i_datasync_tid);
  81        else
  82                commit_tid = atomic_read(&ei->i_sync_tid);
  83
  84        if (test_opt(inode->i_sb, BARRIER) &&
  85            !journal_trans_will_send_data_barrier(journal, commit_tid))
  86                needs_barrier = 1;
  87        log_start_commit(journal, commit_tid);
  88        ret = log_wait_commit(journal, commit_tid);
  89
  90        /*
  91         * In case we didn't commit a transaction, we have to flush
  92         * disk caches manually so that data really is on persistent
  93         * storage
  94         */
  95        if (needs_barrier) {
  96                int err;
  97
  98                err = blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
  99                if (!ret)
 100                        ret = err;
 101        }
 102out:
 103        trace_ext3_sync_file_exit(inode, ret);
 104        return ret;
 105}
 106
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