linux/fs/ext4/fsync.c
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   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 writeback_control wbc;
  48        struct dentry *dentry = NULL;
  49        struct inode *next;
  50        int ret = 0;
  51
  52        if (!ext4_test_inode_state(inode, EXT4_STATE_NEWENTRY))
  53                return 0;
  54        inode = igrab(inode);
  55        while (ext4_test_inode_state(inode, EXT4_STATE_NEWENTRY)) {
  56                ext4_clear_inode_state(inode, EXT4_STATE_NEWENTRY);
  57                dentry = d_find_any_alias(inode);
  58                if (!dentry)
  59                        break;
  60                next = igrab(dentry->d_parent->d_inode);
  61                dput(dentry);
  62                if (!next)
  63                        break;
  64                iput(inode);
  65                inode = next;
  66                ret = sync_mapping_buffers(inode->i_mapping);
  67                if (ret)
  68                        break;
  69                memset(&wbc, 0, sizeof(wbc));
  70                wbc.sync_mode = WB_SYNC_ALL;
  71                wbc.nr_to_write = 0;         /* only write out the inode */
  72                ret = sync_inode(inode, &wbc);
  73                if (ret)
  74                        break;
  75        }
  76        iput(inode);
  77        return ret;
  78}
  79
  80/**
  81 * __sync_file - generic_file_fsync without the locking and filemap_write
  82 * @inode:      inode to sync
  83 * @datasync:   only sync essential metadata if true
  84 *
  85 * This is just generic_file_fsync without the locking.  This is needed for
  86 * nojournal mode to make sure this inodes data/metadata makes it to disk
  87 * properly.  The i_mutex should be held already.
  88 */
  89static int __sync_inode(struct inode *inode, int datasync)
  90{
  91        int err;
  92        int ret;
  93
  94        ret = sync_mapping_buffers(inode->i_mapping);
  95        if (!(inode->i_state & I_DIRTY))
  96                return ret;
  97        if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
  98                return ret;
  99
 100        err = sync_inode_metadata(inode, 1);
 101        if (ret == 0)
 102                ret = err;
 103        return ret;
 104}
 105
 106/*
 107 * akpm: A new design for ext4_sync_file().
 108 *
 109 * This is only called from sys_fsync(), sys_fdatasync() and sys_msync().
 110 * There cannot be a transaction open by this task.
 111 * Another task could have dirtied this inode.  Its data can be in any
 112 * state in the journalling system.
 113 *
 114 * What we do is just kick off a commit and wait on it.  This will snapshot the
 115 * inode to disk.
 116 *
 117 * i_mutex lock is held when entering and exiting this function
 118 */
 119
 120int ext4_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
 121{
 122        struct inode *inode = file->f_mapping->host;
 123        struct ext4_inode_info *ei = EXT4_I(inode);
 124        journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
 125        int ret, err;
 126        tid_t commit_tid;
 127        bool needs_barrier = false;
 128
 129        J_ASSERT(ext4_journal_current_handle() == NULL);
 130
 131        trace_ext4_sync_file_enter(file, datasync);
 132
 133        ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
 134        if (ret)
 135                return ret;
 136        mutex_lock(&inode->i_mutex);
 137
 138        if (inode->i_sb->s_flags & MS_RDONLY)
 139                goto out;
 140
 141        ret = ext4_flush_unwritten_io(inode);
 142        if (ret < 0)
 143                goto out;
 144
 145        if (!journal) {
 146                ret = __sync_inode(inode, datasync);
 147                if (!ret && !hlist_empty(&inode->i_dentry))
 148                        ret = ext4_sync_parent(inode);
 149                goto out;
 150        }
 151
 152        /*
 153         * data=writeback,ordered:
 154         *  The caller's filemap_fdatawrite()/wait will sync the data.
 155         *  Metadata is in the journal, we wait for proper transaction to
 156         *  commit here.
 157         *
 158         * data=journal:
 159         *  filemap_fdatawrite won't do anything (the buffers are clean).
 160         *  ext4_force_commit will write the file data into the journal and
 161         *  will wait on that.
 162         *  filemap_fdatawait() will encounter a ton of newly-dirtied pages
 163         *  (they were dirtied by commit).  But that's OK - the blocks are
 164         *  safe in-journal, which is all fsync() needs to ensure.
 165         */
 166        if (ext4_should_journal_data(inode)) {
 167                ret = ext4_force_commit(inode->i_sb);
 168                goto out;
 169        }
 170
 171        commit_tid = datasync ? ei->i_datasync_tid : ei->i_sync_tid;
 172        if (journal->j_flags & JBD2_BARRIER &&
 173            !jbd2_trans_will_send_data_barrier(journal, commit_tid))
 174                needs_barrier = true;
 175        jbd2_log_start_commit(journal, commit_tid);
 176        ret = jbd2_log_wait_commit(journal, commit_tid);
 177        if (needs_barrier) {
 178                err = blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
 179                if (!ret)
 180                        ret = err;
 181        }
 182 out:
 183        mutex_unlock(&inode->i_mutex);
 184        trace_ext4_sync_file_exit(inode, ret);
 185        return ret;
 186}
 187
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