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 #include "ext4.h"
  32 #include "ext4_jbd2.h"
  33
  34 /*
  35  * akpm: A new design for ext4_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
  46 int ext4_sync_file(struct file * file, struct dentry *dentry, int datasync)
  47 {
  48         struct inode *inode = dentry->d_inode;
  49         journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
  50         int ret = 0;
  51
  52         J_ASSERT(ext4_journal_current_handle() == NULL);
  53
  54         /*
  55          * data=writeback:
  56          *  The caller's filemap_fdatawrite()/wait will sync the data.
  57          *  sync_inode() will sync the metadata
  58          *
  59          * data=ordered:
  60          *  The caller's filemap_fdatawrite() will write the data and
  61          *  sync_inode() will write the inode if it is dirty.  Then the caller's
  62          *  filemap_fdatawait() will wait on the pages.
  63          *
  64          * data=journal:
  65          *  filemap_fdatawrite won't do anything (the buffers are clean).
  66          *  ext4_force_commit will write the file data into the journal and
  67          *  will wait on that.
  68          *  filemap_fdatawait() will encounter a ton of newly-dirtied pages
  69          *  (they were dirtied by commit).  But that's OK - the blocks are
  70          *  safe in-journal, which is all fsync() needs to ensure.
  71          */
  72         if (ext4_should_journal_data(inode)) {
  73                 ret = ext4_force_commit(inode->i_sb);
  74                 goto out;
  75         }
  76
  77         if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
  78                 goto out;
  79
  80         /*
  81          * The VFS has written the file data.  If the inode is unaltered
  82          * then we need not start a commit.
  83          */
  84         if (inode->i_state & (I_DIRTY_SYNC|I_DIRTY_DATASYNC)) {
  85                 struct writeback_control wbc = {
  86                         .sync_mode = WB_SYNC_ALL,
  87                         .nr_to_write = 0, /* sys_fsync did this */
  88                 };
  89                 ret = sync_inode(inode, &wbc);
  90                 if (journal && (journal->j_flags & JBD2_BARRIER))
  91                         blkdev_issue_flush(inode->i_sb->s_bdev, NULL);
  92         }
  93 out:
  94         return ret;
  95 }