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 #include <linux/buffer_head.h>
  32
  33 #include "ext4.h"
  34 #include "ext4_jbd2.h"
  35
  36 #include <trace/events/ext4.h>
  37
  38 /*
  39  * If we're not journaling and this is a just-created file, we have to
  40  * sync our parent directory (if it was freshly created) since
  41  * otherwise it will only be written by writeback, leaving a huge
  42  * window during which a crash may lose the file.  This may apply for
  43  * the parent directory's parent as well, and so on recursively, if
  44  * they are also freshly created.
  45  */
  46 static int ext4_sync_parent(struct inode *inode)
  47 {
  48         struct dentry *dentry, *next;
  49         int ret = 0;
  50
  51         if (!ext4_test_inode_state(inode, EXT4_STATE_NEWENTRY))
  52                 return 0;
  53         dentry = d_find_any_alias(inode);
  54         if (!dentry)
  55                 return 0;
  56         while (ext4_test_inode_state(inode, EXT4_STATE_NEWENTRY)) {
  57                 ext4_clear_inode_state(inode, EXT4_STATE_NEWENTRY);
  58
  59                 next = dget_parent(dentry);
  60                 dput(dentry);
  61                 dentry = next;
  62                 inode = dentry->d_inode;
  63
  64                 /*
  65                  * The directory inode may have gone through rmdir by now. But
  66                  * the inode itself and its blocks are still allocated (we hold
  67                  * a reference to the inode via its dentry), so it didn't go
  68                  * through ext4_evict_inode()) and so we are safe to flush
  69                  * metadata blocks and the inode.
  70                  */
  71                 ret = sync_mapping_buffers(inode->i_mapping);
  72                 if (ret)
  73                         break;
  74                 ret = sync_inode_metadata(inode, 1);
  75                 if (ret)
  76                         break;
  77         }
  78         dput(dentry);
  79         return ret;
  80 }
  81
  82 static int ext4_fsync_nojournal(struct file *file, loff_t start, loff_t end,
  83                                 int datasync, bool *needs_barrier)
  84 {
  85         struct inode *inode = file->f_inode;
  86         int ret;
  87
  88         ret = generic_buffers_fsync_noflush(file, start, end, datasync);
  89         if (!ret)
  90                 ret = ext4_sync_parent(inode);
  91         if (test_opt(inode->i_sb, BARRIER))
  92                 *needs_barrier = true;
  93
  94         return ret;
  95 }
  96
  97 static int ext4_fsync_journal(struct inode *inode, bool datasync,
  98                              bool *needs_barrier)
  99 {
 100         struct ext4_inode_info *ei = EXT4_I(inode);
 101         journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
 102         tid_t commit_tid = datasync ? ei->i_datasync_tid : ei->i_sync_tid;
 103
 104         /*
 105          * Fastcommit does not really support fsync on directories or other
 106          * special files. Force a full commit.
 107          */
 108         if (!S_ISREG(inode->i_mode))
 109                 return ext4_force_commit(inode->i_sb);
 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
 135         if (unlikely(ext4_forced_shutdown(inode->i_sb)))
 136                 return -EIO;
 137
 138         ASSERT(ext4_journal_current_handle() == NULL);
 139
 140         trace_ext4_sync_file_enter(file, datasync);
 141
 142         if (sb_rdonly(inode->i_sb)) {
 143                 /* Make sure that we read updated s_ext4_flags value */
 144                 smp_rmb();
 145                 if (ext4_forced_shutdown(inode->i_sb))
 146                         ret = -EROFS;
 147                 goto out;
 148         }
 149
 150         if (!EXT4_SB(inode->i_sb)->s_journal) {
 151                 ret = ext4_fsync_nojournal(file, start, end, datasync,
 152                                            &needs_barrier);
 153                 if (needs_barrier)
 154                         goto issue_flush;
 155                 goto out;
 156         }
 157
 158         ret = file_write_and_wait_range(file, start, end);
 159         if (ret)
 160                 goto out;
 161
 162         /*
 163          *  The caller's filemap_fdatawrite()/wait will sync the data.
 164          *  Metadata is in the journal, we wait for proper transaction to
 165          *  commit here.
 166          */
 167         ret = ext4_fsync_journal(inode, datasync, &needs_barrier);
 168
 169 issue_flush:
 170         if (needs_barrier) {
 171                 err = blkdev_issue_flush(inode->i_sb->s_bdev);
 172                 if (!ret)
 173                         ret = err;
 174         }
 175 out:
 176         err = file_check_and_advance_wb_err(file);
 177         if (ret == 0)
 178                 ret = err;
 179         trace_ext4_sync_file_exit(inode, ret);
 180         return ret;
 181 }