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  */
  45 static 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
  81 static 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
 104 static 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  */
 129 int 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, GFP_KERNEL);
 178                 if (!ret)
 179                         ret = err;
 180         }
 181 out:
 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 }