LXR linux/fs/ext4/fsync.c

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 *  linux/fs/ext4/fsync.c
   4 *
   5 *  Copyright (C) 1993  Stephen Tweedie (sct@redhat.com)
   6 *  from
   7 *  Copyright (C) 1992  Remy Card (card@masi.ibp.fr)
   8 *                      Laboratoire MASI - Institut Blaise Pascal
   9 *                      Universite Pierre et Marie Curie (Paris VI)
  10 *  from
  11 *  linux/fs/minix/truncate.c   Copyright (C) 1991, 1992  Linus Torvalds
  12 *
  13 *  ext4fs fsync primitive
  14 *
  15 *  Big-endian to little-endian byte-swapping/bitmaps by
  16 *        David S. Miller (davem@caip.rutgers.edu), 1995
  17 *
  18 *  Removed unnecessary code duplication for little endian machines
  19 *  and excessive __inline__s.
  20 *        Andi Kleen, 1997
  21 *
  22 * Major simplications and cleanup - we only need to do the metadata, because
  23 * we can depend on generic_block_fdatasync() to sync the data blocks.
  24 */
  25
  26#include <linux/time.h>
  27#include <linux/fs.h>
  28#include <linux/sched.h>
  29#include <linux/writeback.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, *next;
  48        int ret = 0;
  49
  50        if (!ext4_test_inode_state(inode, EXT4_STATE_NEWENTRY))
  51                return 0;
  52        dentry = d_find_any_alias(inode);
  53        if (!dentry)
  54                return 0;
  55        while (ext4_test_inode_state(inode, EXT4_STATE_NEWENTRY)) {
  56                ext4_clear_inode_state(inode, EXT4_STATE_NEWENTRY);
  57
  58                next = dget_parent(dentry);
  59                dput(dentry);
  60                dentry = next;
  61                inode = dentry->d_inode;
  62
  63                /*
  64                 * The directory inode may have gone through rmdir by now. But
  65                 * the inode itself and its blocks are still allocated (we hold
  66                 * a reference to the inode via its dentry), so it didn't go
  67                 * through ext4_evict_inode()) and so we are safe to flush
  68                 * metadata blocks and the inode.
  69                 */
  70                ret = sync_mapping_buffers(inode->i_mapping);
  71                if (ret)
  72                        break;
  73                ret = sync_inode_metadata(inode, 1);
  74                if (ret)
  75                        break;
  76        }
  77        dput(dentry);
  78        return ret;
  79}
  80
  81static int ext4_fsync_nojournal(struct inode *inode, bool datasync,
  82                                bool *needs_barrier)
  83{
  84        int ret, err;
  85
  86        ret = sync_mapping_buffers(inode->i_mapping);
  87        if (!(inode->i_state & I_DIRTY_ALL))
  88                return ret;
  89        if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
  90                return ret;
  91
  92        err = sync_inode_metadata(inode, 1);
  93        if (!ret)
  94                ret = err;
  95
  96        if (!ret)
  97                ret = ext4_sync_parent(inode);
  98        if (test_opt(inode->i_sb, BARRIER))
  99                *needs_barrier = true;
 100
 101        return ret;
 102}
 103
 104static int ext4_fsync_journal(struct inode *inode, bool datasync,
 105                             bool *needs_barrier)
 106{
 107        struct ext4_inode_info *ei = EXT4_I(inode);
 108        journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
 109        tid_t commit_tid = datasync ? ei->i_datasync_tid : ei->i_sync_tid;
 110
 111        if (journal->j_flags & JBD2_BARRIER &&
 112            !jbd2_trans_will_send_data_barrier(journal, commit_tid))
 113                *needs_barrier = true;
 114
 115        return ext4_fc_commit(journal, commit_tid);
 116}
 117
 118/*
 119 * akpm: A new design for ext4_sync_file().
 120 *
 121 * This is only called from sys_fsync(), sys_fdatasync() and sys_msync().
 122 * There cannot be a transaction open by this task.
 123 * Another task could have dirtied this inode.  Its data can be in any
 124 * state in the journalling system.
 125 *
 126 * What we do is just kick off a commit and wait on it.  This will snapshot the
 127 * inode to disk.
 128 */
 129int ext4_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
 130{
 131        int ret = 0, err;
 132        bool needs_barrier = false;
 133        struct inode *inode = file->f_mapping->host;
 134        struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
 135
 136        if (unlikely(ext4_forced_shutdown(sbi)))
 137                return -EIO;
 138
 139        ASSERT(ext4_journal_current_handle() == NULL);
 140
 141        trace_ext4_sync_file_enter(file, datasync);
 142
 143        if (sb_rdonly(inode->i_sb)) {
 144                /* Make sure that we read updated s_mount_flags value */
 145                smp_rmb();
 146                if (ext4_test_mount_flag(inode->i_sb, EXT4_MF_FS_ABORTED))
 147                        ret = -EROFS;
 148                goto out;
 149        }
 150
 151        ret = file_write_and_wait_range(file, start, end);
 152        if (ret)
 153                goto out;
 154
 155        /*
 156         * data=writeback,ordered:
 157         *  The caller's filemap_fdatawrite()/wait will sync the data.
 158         *  Metadata is in the journal, we wait for proper transaction to
 159         *  commit here.
 160         *
 161         * data=journal:
 162         *  filemap_fdatawrite won't do anything (the buffers are clean).
 163         *  ext4_force_commit will write the file data into the journal and
 164         *  will wait on that.
 165         *  filemap_fdatawait() will encounter a ton of newly-dirtied pages
 166         *  (they were dirtied by commit).  But that's OK - the blocks are
 167         *  safe in-journal, which is all fsync() needs to ensure.
 168         */
 169        if (!sbi->s_journal)
 170                ret = ext4_fsync_nojournal(inode, datasync, &needs_barrier);
 171        else if (ext4_should_journal_data(inode))
 172                ret = ext4_force_commit(inode->i_sb);
 173        else
 174                ret = ext4_fsync_journal(inode, datasync, &needs_barrier);
 175
 176        if (needs_barrier) {
 177                err = blkdev_issue_flush(inode->i_sb->s_bdev);
 178                if (!ret)
 179                        ret = err;
 180        }
 181out:
 182        err = file_check_and_advance_wb_err(file);
 183        if (ret == 0)
 184                ret = err;
 185        trace_ext4_sync_file_exit(inode, ret);
 186        return ret;
 187}
 188