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  * If we're not journaling and this is a just-created file, we have to
  39  * sync our parent directory (if it was freshly created) since
  40  * otherwise it will only be written by writeback, leaving a huge
  41  * window during which a crash may lose the file.  This may apply for
  42  * the parent directory's parent as well, and so on recursively, if
  43  * they are also freshly created.
  44  */
  45 static void ext4_sync_parent(struct inode *inode)
  46 {
  47         struct dentry *dentry = NULL;
  48
  49         while (inode && ext4_test_inode_state(inode, EXT4_STATE_NEWENTRY)) {
  50                 ext4_clear_inode_state(inode, EXT4_STATE_NEWENTRY);
  51                 dentry = list_entry(inode->i_dentry.next,
  52                                     struct dentry, d_alias);
  53                 if (!dentry || !dentry->d_parent || !dentry->d_parent->d_inode)
  54                         break;
  55                 inode = dentry->d_parent->d_inode;
  56                 sync_mapping_buffers(inode->i_mapping);
  57         }
  58 }
  59
  60 /*
  61  * akpm: A new design for ext4_sync_file().
  62  *
  63  * This is only called from sys_fsync(), sys_fdatasync() and sys_msync().
  64  * There cannot be a transaction open by this task.
  65  * Another task could have dirtied this inode.  Its data can be in any
  66  * state in the journalling system.
  67  *
  68  * What we do is just kick off a commit and wait on it.  This will snapshot the
  69  * inode to disk.
  70  *
  71  * i_mutex lock is held when entering and exiting this function
  72  */
  73
  74 int ext4_sync_file(struct file *file, int datasync)
  75 {
  76         struct inode *inode = file->f_mapping->host;
  77         struct ext4_inode_info *ei = EXT4_I(inode);
  78         journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
  79         int ret;
  80         tid_t commit_tid;
  81
  82         J_ASSERT(ext4_journal_current_handle() == NULL);
  83
  84         trace_ext4_sync_file(file, datasync);
  85
  86         if (inode->i_sb->s_flags & MS_RDONLY)
  87                 return 0;
  88
  89         ret = flush_completed_IO(inode);
  90         if (ret < 0)
  91                 return ret;
  92
  93         if (!journal) {
  94                 ret = generic_file_fsync(file, datasync);
  95                 if (!ret && !list_empty(&inode->i_dentry))
  96                         ext4_sync_parent(inode);
  97                 return ret;
  98         }
  99
 100         /*
 101          * data=writeback,ordered:
 102          *  The caller's filemap_fdatawrite()/wait will sync the data.
 103          *  Metadata is in the journal, we wait for proper transaction to
 104          *  commit here.
 105          *
 106          * data=journal:
 107          *  filemap_fdatawrite won't do anything (the buffers are clean).
 108          *  ext4_force_commit will write the file data into the journal and
 109          *  will wait on that.
 110          *  filemap_fdatawait() will encounter a ton of newly-dirtied pages
 111          *  (they were dirtied by commit).  But that's OK - the blocks are
 112          *  safe in-journal, which is all fsync() needs to ensure.
 113          */
 114         if (ext4_should_journal_data(inode))
 115                 return ext4_force_commit(inode->i_sb);
 116
 117         commit_tid = datasync ? ei->i_datasync_tid : ei->i_sync_tid;
 118         if (jbd2_log_start_commit(journal, commit_tid)) {
 119                 /*
 120                  * When the journal is on a different device than the
 121                  * fs data disk, we need to issue the barrier in
 122                  * writeback mode.  (In ordered mode, the jbd2 layer
 123                  * will take care of issuing the barrier.  In
 124                  * data=journal, all of the data blocks are written to
 125                  * the journal device.)
 126                  */
 127                 if (ext4_should_writeback_data(inode) &&
 128                     (journal->j_fs_dev != journal->j_dev) &&
 129                     (journal->j_flags & JBD2_BARRIER))
 130                         blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL,
 131                                         NULL);
 132                 ret = jbd2_log_wait_commit(journal, commit_tid);
 133         } else if (journal->j_flags & JBD2_BARRIER)
 134                 blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
 135         return ret;
 136 }