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 "ext4.h"
  31 #include "ext4_jbd2.h"
  32
  33 /*
  34  * akpm: A new design for ext4_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
  45 int ext4_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(ext4_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          *  ext4_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 (ext4_should_journal_data(inode)) {
  71                 ret = ext4_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         }
  89 out:
  90         return ret;
  91 }