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/blkdev.h>
  30
  31#include "ext4.h"
  32#include "ext4_jbd2.h"
  33
  34#include <trace/events/ext4.h>
  35
  36/*
  37 * If we're not journaling and this is a just-created file, we have to
  38 * sync our parent directory (if it was freshly created) since
  39 * otherwise it will only be written by writeback, leaving a huge
  40 * window during which a crash may lose the file.  This may apply for
  41 * the parent directory's parent as well, and so on recursively, if
  42 * they are also freshly created.
  43 */
  44static int ext4_sync_parent(struct inode *inode)
  45{
  46        struct dentry *dentry = NULL;
  47        struct inode *next;
  48        int ret = 0;
  49
  50        if (!ext4_test_inode_state(inode, EXT4_STATE_NEWENTRY))
  51                return 0;
  52        inode = igrab(inode);
  53        while (ext4_test_inode_state(inode, EXT4_STATE_NEWENTRY)) {
  54                ext4_clear_inode_state(inode, EXT4_STATE_NEWENTRY);
  55                dentry = d_find_any_alias(inode);
  56                if (!dentry)
  57                        break;
  58                next = igrab(d_inode(dentry->d_parent));
  59                dput(dentry);
  60                if (!next)
  61                        break;
  62                iput(inode);
  63                inode = next;
  64                ret = sync_mapping_buffers(inode->i_mapping);
  65                if (ret)
  66                        break;
  67                ret = sync_inode_metadata(inode, 1);
  68                if (ret)
  69                        break;
  70        }
  71        iput(inode);
  72        return ret;
  73}
  74
  75/*
  76 * akpm: A new design for ext4_sync_file().
  77 *
  78 * This is only called from sys_fsync(), sys_fdatasync() and sys_msync().
  79 * There cannot be a transaction open by this task.
  80 * Another task could have dirtied this inode.  Its data can be in any
  81 * state in the journalling system.
  82 *
  83 * What we do is just kick off a commit and wait on it.  This will snapshot the
  84 * inode to disk.
  85 */
  86
  87int ext4_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
  88{
  89        struct inode *inode = file->f_mapping->host;
  90        struct ext4_inode_info *ei = EXT4_I(inode);
  91        journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
  92        int ret = 0, err;
  93        tid_t commit_tid;
  94        bool needs_barrier = false;
  95
  96        J_ASSERT(ext4_journal_current_handle() == NULL);
  97
  98        trace_ext4_sync_file_enter(file, datasync);
  99
 100        if (inode->i_sb->s_flags & MS_RDONLY) {
 101                /* Make sure that we read updated s_mount_flags value */
 102                smp_rmb();
 103                if (EXT4_SB(inode->i_sb)->s_mount_flags & EXT4_MF_FS_ABORTED)
 104                        ret = -EROFS;
 105                goto out;
 106        }
 107
 108        if (!journal) {
 109                ret = generic_file_fsync(file, start, end, datasync);
 110                if (!ret && !hlist_empty(&inode->i_dentry))
 111                        ret = ext4_sync_parent(inode);
 112                goto out;
 113        }
 114
 115        ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
 116        if (ret)
 117                return ret;
 118        /*
 119         * data=writeback,ordered:
 120         *  The caller's filemap_fdatawrite()/wait will sync the data.
 121         *  Metadata is in the journal, we wait for proper transaction to
 122         *  commit here.
 123         *
 124         * data=journal:
 125         *  filemap_fdatawrite won't do anything (the buffers are clean).
 126         *  ext4_force_commit will write the file data into the journal and
 127         *  will wait on that.
 128         *  filemap_fdatawait() will encounter a ton of newly-dirtied pages
 129         *  (they were dirtied by commit).  But that's OK - the blocks are
 130         *  safe in-journal, which is all fsync() needs to ensure.
 131         */
 132        if (ext4_should_journal_data(inode)) {
 133                ret = ext4_force_commit(inode->i_sb);
 134                goto out;
 135        }
 136
 137        commit_tid = datasync ? ei->i_datasync_tid : ei->i_sync_tid;
 138        if (journal->j_flags & JBD2_BARRIER &&
 139            !jbd2_trans_will_send_data_barrier(journal, commit_tid))
 140                needs_barrier = true;
 141        ret = jbd2_complete_transaction(journal, commit_tid);
 142        if (needs_barrier) {
 143                err = blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
 144                if (!ret)
 145                        ret = err;
 146        }
 147out:
 148        trace_ext4_sync_file_exit(inode, ret);
 149        return ret;
 150}
 151