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
  51 int ext4_sync_file(struct file *file, struct dentry *dentry, int datasync)
  52 {
  53         struct inode *inode = dentry->d_inode;
  54         struct ext4_inode_info *ei = EXT4_I(inode);
  55         journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
  56         int ret;
  57         tid_t commit_tid;
  58
  59         J_ASSERT(ext4_journal_current_handle() == NULL);
  60
  61         trace_ext4_sync_file(file, dentry, datasync);
  62
  63         if (inode->i_sb->s_flags & MS_RDONLY)
  64                 return 0;
  65
  66         ret = flush_completed_IO(inode);
  67         if (ret < 0)
  68                 return ret;
  69
  70         if (!journal)
  71                 return simple_fsync(file, dentry, datasync);
  72
  73         /*
  74          * data=writeback,ordered:
  75          *  The caller's filemap_fdatawrite()/wait will sync the data.
  76          *  Metadata is in the journal, we wait for proper transaction to
  77          *  commit here.
  78          *
  79          * data=journal:
  80          *  filemap_fdatawrite won't do anything (the buffers are clean).
  81          *  ext4_force_commit will write the file data into the journal and
  82          *  will wait on that.
  83          *  filemap_fdatawait() will encounter a ton of newly-dirtied pages
  84          *  (they were dirtied by commit).  But that's OK - the blocks are
  85          *  safe in-journal, which is all fsync() needs to ensure.
  86          */
  87         if (ext4_should_journal_data(inode))
  88                 return ext4_force_commit(inode->i_sb);
  89
  90         commit_tid = datasync ? ei->i_datasync_tid : ei->i_sync_tid;
  91         if (jbd2_log_start_commit(journal, commit_tid)) {
  92                 /*
  93                  * When the journal is on a different device than the
  94                  * fs data disk, we need to issue the barrier in
  95                  * writeback mode.  (In ordered mode, the jbd2 layer
  96                  * will take care of issuing the barrier.  In
  97                  * data=journal, all of the data blocks are written to
  98                  * the journal device.)
  99                  */
 100                 if (ext4_should_writeback_data(inode) &&
 101                     (journal->j_fs_dev != journal->j_dev) &&
 102                     (journal->j_flags & JBD2_BARRIER))
 103                         blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL,
 104                                         NULL, BLKDEV_IFL_WAIT);
 105                 jbd2_log_wait_commit(journal, commit_tid);
 106         } else if (journal->j_flags & JBD2_BARRIER)
 107                 blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL,
 108                         BLKDEV_IFL_WAIT);
 109         return ret;
 110 }