LXR linux/fs/ext4/fsync.c

   1/*
   2 *  linux/fs/ext4/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 *  ext4fs 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/jbd2.h>
  30#include <linux/blkdev.h>
  31
  32#include "ext4.h"
  33#include "ext4_jbd2.h"
  34
  35#include <trace/events/ext4.h>
  36
  37/*
  38 * akpm: A new design for ext4_sync_file().
  39 *
  40 * This is only called from sys_fsync(), sys_fdatasync() and sys_msync().
  41 * There cannot be a transaction open by this task.
  42 * Another task could have dirtied this inode.  Its data can be in any
  43 * state in the journalling system.
  44 *
  45 * What we do is just kick off a commit and wait on it.  This will snapshot the
  46 * inode to disk.
  47 *
  48 * i_mutex lock is held when entering and exiting this function
  49 */
  50
  51int ext4_sync_file(struct file *file, struct dentry *dentry, int datasync)
  52{
  53        struct inode *inode = dentry->d_inode;
  54        journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
  55        int err, ret = 0;
  56
  57        J_ASSERT(ext4_journal_current_handle() == NULL);
  58
  59        trace_ext4_sync_file(file, dentry, datasync);
  60
  61        ret = flush_aio_dio_completed_IO(inode);
  62        if (ret < 0)
  63                goto out;
  64        /*
  65         * data=writeback:
  66         *  The caller's filemap_fdatawrite()/wait will sync the data.
  67         *  sync_inode() will sync the metadata
  68         *
  69         * data=ordered:
  70         *  The caller's filemap_fdatawrite() will write the data and
  71         *  sync_inode() will write the inode if it is dirty.  Then the caller's
  72         *  filemap_fdatawait() will wait on the pages.
  73         *
  74         * data=journal:
  75         *  filemap_fdatawrite won't do anything (the buffers are clean).
  76         *  ext4_force_commit will write the file data into the journal and
  77         *  will wait on that.
  78         *  filemap_fdatawait() will encounter a ton of newly-dirtied pages
  79         *  (they were dirtied by commit).  But that's OK - the blocks are
  80         *  safe in-journal, which is all fsync() needs to ensure.
  81         */
  82        if (ext4_should_journal_data(inode)) {
  83                ret = ext4_force_commit(inode->i_sb);
  84                goto out;
  85        }
  86
  87        if (!journal)
  88                ret = sync_mapping_buffers(inode->i_mapping);
  89
  90        if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
  91                goto out;
  92
  93        /*
  94         * The VFS has written the file data.  If the inode is unaltered
  95         * then we need not start a commit.
  96         */
  97        if (inode->i_state & (I_DIRTY_SYNC|I_DIRTY_DATASYNC)) {
  98                struct writeback_control wbc = {
  99                        .sync_mode = WB_SYNC_ALL,
 100                        .nr_to_write = 0, /* sys_fsync did this */
 101                };
 102                err = sync_inode(inode, &wbc);
 103                if (ret == 0)
 104                        ret = err;
 105        }
 106out:
 107        if (journal && (journal->j_flags & JBD2_BARRIER))
 108                blkdev_issue_flush(inode->i_sb->s_bdev, NULL);
 109        return ret;
 110}
 111