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/jbd2.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 static void dump_completed_IO(struct inode * inode)
  38 {
  39 #ifdef  EXT4FS_DEBUG
  40         struct list_head *cur, *before, *after;
  41         ext4_io_end_t *io, *io0, *io1;
  42         unsigned long flags;
  43
  44         if (list_empty(&EXT4_I(inode)->i_completed_io_list)){
  45                 ext4_debug("inode %lu completed_io list is empty\n", inode->i_ino);
  46                 return;
  47         }
  48
  49         ext4_debug("Dump inode %lu completed_io list \n", inode->i_ino);
  50         spin_lock_irqsave(&EXT4_I(inode)->i_completed_io_lock, flags);
  51         list_for_each_entry(io, &EXT4_I(inode)->i_completed_io_list, list){
  52                 cur = &io->list;
  53                 before = cur->prev;
  54                 io0 = container_of(before, ext4_io_end_t, list);
  55                 after = cur->next;
  56                 io1 = container_of(after, ext4_io_end_t, list);
  57
  58                 ext4_debug("io 0x%p from inode %lu,prev 0x%p,next 0x%p\n",
  59                             io, inode->i_ino, io0, io1);
  60         }
  61         spin_unlock_irqrestore(&EXT4_I(inode)->i_completed_io_lock, flags);
  62 #endif
  63 }
  64
  65 /*
  66  * This function is called from ext4_sync_file().
  67  *
  68  * When IO is completed, the work to convert unwritten extents to
  69  * written is queued on workqueue but may not get immediately
  70  * scheduled. When fsync is called, we need to ensure the
  71  * conversion is complete before fsync returns.
  72  * The inode keeps track of a list of pending/completed IO that
  73  * might needs to do the conversion. This function walks through
  74  * the list and convert the related unwritten extents for completed IO
  75  * to written.
  76  * The function return the number of pending IOs on success.
  77  */
  78 int ext4_flush_completed_IO(struct inode *inode)
  79 {
  80         ext4_io_end_t *io;
  81         struct ext4_inode_info *ei = EXT4_I(inode);
  82         unsigned long flags;
  83         int ret = 0;
  84         int ret2 = 0;
  85
  86         dump_completed_IO(inode);
  87         spin_lock_irqsave(&ei->i_completed_io_lock, flags);
  88         while (!list_empty(&ei->i_completed_io_list)){
  89                 io = list_entry(ei->i_completed_io_list.next,
  90                                 ext4_io_end_t, list);
  91                 list_del_init(&io->list);
  92                 io->flag |= EXT4_IO_END_IN_FSYNC;
  93                 /*
  94                  * Calling ext4_end_io_nolock() to convert completed
  95                  * IO to written.
  96                  *
  97                  * When ext4_sync_file() is called, run_queue() may already
  98                  * about to flush the work corresponding to this io structure.
  99                  * It will be upset if it founds the io structure related
 100                  * to the work-to-be schedule is freed.
 101                  *
 102                  * Thus we need to keep the io structure still valid here after
 103                  * conversion finished. The io structure has a flag to
 104                  * avoid double converting from both fsync and background work
 105                  * queue work.
 106                  */
 107                 spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
 108                 ret = ext4_end_io_nolock(io);
 109                 if (ret < 0)
 110                         ret2 = ret;
 111                 spin_lock_irqsave(&ei->i_completed_io_lock, flags);
 112                 io->flag &= ~EXT4_IO_END_IN_FSYNC;
 113         }
 114         spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
 115         return (ret2 < 0) ? ret2 : 0;
 116 }
 117
 118 /*
 119  * If we're not journaling and this is a just-created file, we have to
 120  * sync our parent directory (if it was freshly created) since
 121  * otherwise it will only be written by writeback, leaving a huge
 122  * window during which a crash may lose the file.  This may apply for
 123  * the parent directory's parent as well, and so on recursively, if
 124  * they are also freshly created.
 125  */
 126 static int ext4_sync_parent(struct inode *inode)
 127 {
 128         struct writeback_control wbc;
 129         struct dentry *dentry = NULL;
 130         struct inode *next;
 131         int ret = 0;
 132
 133         if (!ext4_test_inode_state(inode, EXT4_STATE_NEWENTRY))
 134                 return 0;
 135         inode = igrab(inode);
 136         while (ext4_test_inode_state(inode, EXT4_STATE_NEWENTRY)) {
 137                 ext4_clear_inode_state(inode, EXT4_STATE_NEWENTRY);
 138                 dentry = NULL;
 139                 spin_lock(&inode->i_lock);
 140                 if (!list_empty(&inode->i_dentry)) {
 141                         dentry = list_first_entry(&inode->i_dentry,
 142                                                   struct dentry, d_alias);
 143                         dget(dentry);
 144                 }
 145                 spin_unlock(&inode->i_lock);
 146                 if (!dentry)
 147                         break;
 148                 next = igrab(dentry->d_parent->d_inode);
 149                 dput(dentry);
 150                 if (!next)
 151                         break;
 152                 iput(inode);
 153                 inode = next;
 154                 ret = sync_mapping_buffers(inode->i_mapping);
 155                 if (ret)
 156                         break;
 157                 memset(&wbc, 0, sizeof(wbc));
 158                 wbc.sync_mode = WB_SYNC_ALL;
 159                 wbc.nr_to_write = 0;         /* only write out the inode */
 160                 ret = sync_inode(inode, &wbc);
 161                 if (ret)
 162                         break;
 163         }
 164         iput(inode);
 165         return ret;
 166 }
 167
 168 /**
 169  * __sync_file - generic_file_fsync without the locking and filemap_write
 170  * @inode:      inode to sync
 171  * @datasync:   only sync essential metadata if true
 172  *
 173  * This is just generic_file_fsync without the locking.  This is needed for
 174  * nojournal mode to make sure this inodes data/metadata makes it to disk
 175  * properly.  The i_mutex should be held already.
 176  */
 177 static int __sync_inode(struct inode *inode, int datasync)
 178 {
 179         int err;
 180         int ret;
 181
 182         ret = sync_mapping_buffers(inode->i_mapping);
 183         if (!(inode->i_state & I_DIRTY))
 184                 return ret;
 185         if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
 186                 return ret;
 187
 188         err = sync_inode_metadata(inode, 1);
 189         if (ret == 0)
 190                 ret = err;
 191         return ret;
 192 }
 193
 194 /*
 195  * akpm: A new design for ext4_sync_file().
 196  *
 197  * This is only called from sys_fsync(), sys_fdatasync() and sys_msync().
 198  * There cannot be a transaction open by this task.
 199  * Another task could have dirtied this inode.  Its data can be in any
 200  * state in the journalling system.
 201  *
 202  * What we do is just kick off a commit and wait on it.  This will snapshot the
 203  * inode to disk.
 204  *
 205  * i_mutex lock is held when entering and exiting this function
 206  */
 207
 208 int ext4_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
 209 {
 210         struct inode *inode = file->f_mapping->host;
 211         struct ext4_inode_info *ei = EXT4_I(inode);
 212         journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
 213         int ret;
 214         tid_t commit_tid;
 215         bool needs_barrier = false;
 216
 217         J_ASSERT(ext4_journal_current_handle() == NULL);
 218
 219         trace_ext4_sync_file_enter(file, datasync);
 220
 221         ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
 222         if (ret)
 223                 return ret;
 224         mutex_lock(&inode->i_mutex);
 225
 226         if (inode->i_sb->s_flags & MS_RDONLY)
 227                 goto out;
 228
 229         ret = ext4_flush_completed_IO(inode);
 230         if (ret < 0)
 231                 goto out;
 232
 233         if (!journal) {
 234                 ret = __sync_inode(inode, datasync);
 235                 if (!ret && !list_empty(&inode->i_dentry))
 236                         ret = ext4_sync_parent(inode);
 237                 goto out;
 238         }
 239
 240         /*
 241          * data=writeback,ordered:
 242          *  The caller's filemap_fdatawrite()/wait will sync the data.
 243          *  Metadata is in the journal, we wait for proper transaction to
 244          *  commit here.
 245          *
 246          * data=journal:
 247          *  filemap_fdatawrite won't do anything (the buffers are clean).
 248          *  ext4_force_commit will write the file data into the journal and
 249          *  will wait on that.
 250          *  filemap_fdatawait() will encounter a ton of newly-dirtied pages
 251          *  (they were dirtied by commit).  But that's OK - the blocks are
 252          *  safe in-journal, which is all fsync() needs to ensure.
 253          */
 254         if (ext4_should_journal_data(inode)) {
 255                 ret = ext4_force_commit(inode->i_sb);
 256                 goto out;
 257         }
 258
 259         commit_tid = datasync ? ei->i_datasync_tid : ei->i_sync_tid;
 260         if (journal->j_flags & JBD2_BARRIER &&
 261             !jbd2_trans_will_send_data_barrier(journal, commit_tid))
 262                 needs_barrier = true;
 263         jbd2_log_start_commit(journal, commit_tid);
 264         ret = jbd2_log_wait_commit(journal, commit_tid);
 265         if (needs_barrier)
 266                 blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
 267  out:
 268         mutex_unlock(&inode->i_mutex);
 269         trace_ext4_sync_file_exit(inode, ret);
 270         return ret;
 271 }