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 = NULL;
  48         struct inode *next;
  49         int ret = 0;
  50
  51         if (!ext4_test_inode_state(inode, EXT4_STATE_NEWENTRY))
  52                 return 0;
  53         inode = igrab(inode);
  54         while (ext4_test_inode_state(inode, EXT4_STATE_NEWENTRY)) {
  55                 ext4_clear_inode_state(inode, EXT4_STATE_NEWENTRY);
  56                 dentry = d_find_any_alias(inode);
  57                 if (!dentry)
  58                         break;
  59                 next = igrab(d_inode(dentry->d_parent));
  60                 dput(dentry);
  61                 if (!next)
  62                         break;
  63                 iput(inode);
  64                 inode = next;
  65                 /*
  66                  * The directory inode may have gone through rmdir by now. But
  67                  * the inode itself and its blocks are still allocated (we hold
  68                  * a reference to the inode so it didn't go through
  69                  * ext4_evict_inode()) and so we are safe to flush metadata
  70                  * blocks and the inode.
  71                  */
  72                 ret = sync_mapping_buffers(inode->i_mapping);
  73                 if (ret)
  74                         break;
  75                 ret = sync_inode_metadata(inode, 1);
  76                 if (ret)
  77                         break;
  78         }
  79         iput(inode);
  80         return ret;
  81 }
  82
  83 /*
  84  * akpm: A new design for ext4_sync_file().
  85  *
  86  * This is only called from sys_fsync(), sys_fdatasync() and sys_msync().
  87  * There cannot be a transaction open by this task.
  88  * Another task could have dirtied this inode.  Its data can be in any
  89  * state in the journalling system.
  90  *
  91  * What we do is just kick off a commit and wait on it.  This will snapshot the
  92  * inode to disk.
  93  */
  94
  95 int ext4_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
  96 {
  97         struct inode *inode = file->f_mapping->host;
  98         struct ext4_inode_info *ei = EXT4_I(inode);
  99         journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
 100         int ret = 0, err;
 101         tid_t commit_tid;
 102         bool needs_barrier = false;
 103
 104         if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
 105                 return -EIO;
 106
 107         J_ASSERT(ext4_journal_current_handle() == NULL);
 108
 109         trace_ext4_sync_file_enter(file, datasync);
 110
 111         if (sb_rdonly(inode->i_sb)) {
 112                 /* Make sure that we read updated s_mount_flags value */
 113                 smp_rmb();
 114                 if (EXT4_SB(inode->i_sb)->s_mount_flags & EXT4_MF_FS_ABORTED)
 115                         ret = -EROFS;
 116                 goto out;
 117         }
 118
 119         if (!journal) {
 120                 ret = __generic_file_fsync(file, start, end, datasync);
 121                 if (!ret)
 122                         ret = ext4_sync_parent(inode);
 123                 if (test_opt(inode->i_sb, BARRIER))
 124                         goto issue_flush;
 125                 goto out;
 126         }
 127
 128         ret = file_write_and_wait_range(file, start, end);
 129         if (ret)
 130                 return ret;
 131         /*
 132          * data=writeback,ordered:
 133          *  The caller's filemap_fdatawrite()/wait will sync the data.
 134          *  Metadata is in the journal, we wait for proper transaction to
 135          *  commit here.
 136          *
 137          * data=journal:
 138          *  filemap_fdatawrite won't do anything (the buffers are clean).
 139          *  ext4_force_commit will write the file data into the journal and
 140          *  will wait on that.
 141          *  filemap_fdatawait() will encounter a ton of newly-dirtied pages
 142          *  (they were dirtied by commit).  But that's OK - the blocks are
 143          *  safe in-journal, which is all fsync() needs to ensure.
 144          */
 145         if (ext4_should_journal_data(inode)) {
 146                 ret = ext4_force_commit(inode->i_sb);
 147                 goto out;
 148         }
 149
 150         commit_tid = datasync ? ei->i_datasync_tid : ei->i_sync_tid;
 151         if (journal->j_flags & JBD2_BARRIER &&
 152             !jbd2_trans_will_send_data_barrier(journal, commit_tid))
 153                 needs_barrier = true;
 154         ret = jbd2_complete_transaction(journal, commit_tid);
 155         if (needs_barrier) {
 156         issue_flush:
 157                 err = blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
 158                 if (!ret)
 159                         ret = err;
 160         }
 161 out:
 162         trace_ext4_sync_file_exit(inode, ret);
 163         return ret;
 164 }