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 * 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 */
  45static int ext4_sync_parent(struct inode *inode)
  46{
  47        struct dentry *dentry = NULL;
  48        struct inode *next;
  49        int ret = 0;
  50
  51        if (!ext4_test_inode_state(inode, EXT4_STATE_NEWENTRY))
  52                return 0;
  53        inode = igrab(inode);
  54        while (ext4_test_inode_state(inode, EXT4_STATE_NEWENTRY)) {
  55                ext4_clear_inode_state(inode, EXT4_STATE_NEWENTRY);
  56                dentry = d_find_any_alias(inode);
  57                if (!dentry)
  58                        break;
  59                next = igrab(dentry->d_parent->d_inode);
  60                dput(dentry);
  61                if (!next)
  62                        break;
  63                iput(inode);
  64                inode = next;
  65                ret = sync_mapping_buffers(inode->i_mapping);
  66                if (ret)
  67                        break;
  68                ret = sync_inode_metadata(inode, 1);
  69                if (ret)
  70                        break;
  71        }
  72        iput(inode);
  73        return ret;
  74}
  75
  76/**
  77 * __sync_file - generic_file_fsync without the locking and filemap_write
  78 * @inode:      inode to sync
  79 * @datasync:   only sync essential metadata if true
  80 *
  81 * This is just generic_file_fsync without the locking.  This is needed for
  82 * nojournal mode to make sure this inodes data/metadata makes it to disk
  83 * properly.  The i_mutex should be held already.
  84 */
  85static int __sync_inode(struct inode *inode, int datasync)
  86{
  87        int err;
  88        int ret;
  89
  90        ret = sync_mapping_buffers(inode->i_mapping);
  91        if (!(inode->i_state & I_DIRTY))
  92                return ret;
  93        if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
  94                return ret;
  95
  96        err = sync_inode_metadata(inode, 1);
  97        if (ret == 0)
  98                ret = err;
  99        return ret;
 100}
 101
 102/*
 103 * akpm: A new design for ext4_sync_file().
 104 *
 105 * This is only called from sys_fsync(), sys_fdatasync() and sys_msync().
 106 * There cannot be a transaction open by this task.
 107 * Another task could have dirtied this inode.  Its data can be in any
 108 * state in the journalling system.
 109 *
 110 * What we do is just kick off a commit and wait on it.  This will snapshot the
 111 * inode to disk.
 112 */
 113
 114int ext4_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
 115{
 116        struct inode *inode = file->f_mapping->host;
 117        struct ext4_inode_info *ei = EXT4_I(inode);
 118        journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
 119        int ret, err;
 120        tid_t commit_tid;
 121        bool needs_barrier = false;
 122
 123        J_ASSERT(ext4_journal_current_handle() == NULL);
 124
 125        trace_ext4_sync_file_enter(file, datasync);
 126
 127        ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
 128        if (ret)
 129                return ret;
 130        mutex_lock(&inode->i_mutex);
 131
 132        if (inode->i_sb->s_flags & MS_RDONLY)
 133                goto out;
 134
 135        ret = ext4_flush_unwritten_io(inode);
 136        if (ret < 0)
 137                goto out;
 138
 139        if (!journal) {
 140                ret = __sync_inode(inode, datasync);
 141                if (!ret && !hlist_empty(&inode->i_dentry))
 142                        ret = ext4_sync_parent(inode);
 143                goto out;
 144        }
 145
 146        /*
 147         * data=writeback,ordered:
 148         *  The caller's filemap_fdatawrite()/wait will sync the data.
 149         *  Metadata is in the journal, we wait for proper transaction to
 150         *  commit here.
 151         *
 152         * data=journal:
 153         *  filemap_fdatawrite won't do anything (the buffers are clean).
 154         *  ext4_force_commit will write the file data into the journal and
 155         *  will wait on that.
 156         *  filemap_fdatawait() will encounter a ton of newly-dirtied pages
 157         *  (they were dirtied by commit).  But that's OK - the blocks are
 158         *  safe in-journal, which is all fsync() needs to ensure.
 159         */
 160        if (ext4_should_journal_data(inode)) {
 161                ret = ext4_force_commit(inode->i_sb);
 162                goto out;
 163        }
 164
 165        commit_tid = datasync ? ei->i_datasync_tid : ei->i_sync_tid;
 166        if (journal->j_flags & JBD2_BARRIER &&
 167            !jbd2_trans_will_send_data_barrier(journal, commit_tid))
 168                needs_barrier = true;
 169        ret = jbd2_complete_transaction(journal, commit_tid);
 170        if (needs_barrier) {
 171                err = blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
 172                if (!ret)
 173                        ret = err;
 174        }
 175 out:
 176        mutex_unlock(&inode->i_mutex);
 177        trace_ext4_sync_file_exit(inode, ret);
 178        return ret;
 179}
 180