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 extern 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         if (list_empty(&ei->i_completed_io_list))
  87                 return ret;
  88
  89         dump_completed_IO(inode);
  90         spin_lock_irqsave(&ei->i_completed_io_lock, flags);
  91         while (!list_empty(&ei->i_completed_io_list)){
  92                 io = list_entry(ei->i_completed_io_list.next,
  93                                 ext4_io_end_t, list);
  94                 /*
  95                  * Calling ext4_end_io_nolock() to convert completed
  96                  * IO to written.
  97                  *
  98                  * When ext4_sync_file() is called, run_queue() may already
  99                  * about to flush the work corresponding to this io structure.
 100                  * It will be upset if it founds the io structure related
 101                  * to the work-to-be schedule is freed.
 102                  *
 103                  * Thus we need to keep the io structure still valid here after
 104                  * conversion finished. The io structure has a flag to
 105                  * avoid double converting from both fsync and background work
 106                  * queue work.
 107                  */
 108                 spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
 109                 ret = ext4_end_io_nolock(io);
 110                 spin_lock_irqsave(&ei->i_completed_io_lock, flags);
 111                 if (ret < 0)
 112                         ret2 = ret;
 113                 else
 114                         list_del_init(&io->list);
 115         }
 116         spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
 117         return (ret2 < 0) ? ret2 : 0;
 118 }
 119
 120 /*
 121  * If we're not journaling and this is a just-created file, we have to
 122  * sync our parent directory (if it was freshly created) since
 123  * otherwise it will only be written by writeback, leaving a huge
 124  * window during which a crash may lose the file.  This may apply for
 125  * the parent directory's parent as well, and so on recursively, if
 126  * they are also freshly created.
 127  */
 128 static int ext4_sync_parent(struct inode *inode)
 129 {
 130         struct writeback_control wbc;
 131         struct dentry *dentry = NULL;
 132         struct inode *next;
 133         int ret = 0;
 134
 135         if (!ext4_test_inode_state(inode, EXT4_STATE_NEWENTRY))
 136                 return 0;
 137         inode = igrab(inode);
 138         while (ext4_test_inode_state(inode, EXT4_STATE_NEWENTRY)) {
 139                 ext4_clear_inode_state(inode, EXT4_STATE_NEWENTRY);
 140                 dentry = NULL;
 141                 spin_lock(&inode->i_lock);
 142                 if (!list_empty(&inode->i_dentry)) {
 143                         dentry = list_first_entry(&inode->i_dentry,
 144                                                   struct dentry, d_alias);
 145                         dget(dentry);
 146                 }
 147                 spin_unlock(&inode->i_lock);
 148                 if (!dentry)
 149                         break;
 150                 next = igrab(dentry->d_parent->d_inode);
 151                 dput(dentry);
 152                 if (!next)
 153                         break;
 154                 iput(inode);
 155                 inode = next;
 156                 ret = sync_mapping_buffers(inode->i_mapping);
 157                 if (ret)
 158                         break;
 159                 memset(&wbc, 0, sizeof(wbc));
 160                 wbc.sync_mode = WB_SYNC_ALL;
 161                 wbc.nr_to_write = 0;         /* only write out the inode */
 162                 ret = sync_inode(inode, &wbc);
 163                 if (ret)
 164                         break;
 165         }
 166         iput(inode);
 167         return ret;
 168 }
 169
 170 /**
 171  * __sync_file - generic_file_fsync without the locking and filemap_write
 172  * @inode:      inode to sync
 173  * @datasync:   only sync essential metadata if true
 174  *
 175  * This is just generic_file_fsync without the locking.  This is needed for
 176  * nojournal mode to make sure this inodes data/metadata makes it to disk
 177  * properly.  The i_mutex should be held already.
 178  */
 179 static int __sync_inode(struct inode *inode, int datasync)
 180 {
 181         int err;
 182         int ret;
 183
 184         ret = sync_mapping_buffers(inode->i_mapping);
 185         if (!(inode->i_state & I_DIRTY))
 186                 return ret;
 187         if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
 188                 return ret;
 189
 190         err = sync_inode_metadata(inode, 1);
 191         if (ret == 0)
 192                 ret = err;
 193         return ret;
 194 }
 195
 196 /*
 197  * akpm: A new design for ext4_sync_file().
 198  *
 199  * This is only called from sys_fsync(), sys_fdatasync() and sys_msync().
 200  * There cannot be a transaction open by this task.
 201  * Another task could have dirtied this inode.  Its data can be in any
 202  * state in the journalling system.
 203  *
 204  * What we do is just kick off a commit and wait on it.  This will snapshot the
 205  * inode to disk.
 206  *
 207  * i_mutex lock is held when entering and exiting this function
 208  */
 209
 210 int ext4_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
 211 {
 212         struct inode *inode = file->f_mapping->host;
 213         struct ext4_inode_info *ei = EXT4_I(inode);
 214         journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
 215         int ret;
 216         tid_t commit_tid;
 217         bool needs_barrier = false;
 218
 219         J_ASSERT(ext4_journal_current_handle() == NULL);
 220
 221         trace_ext4_sync_file_enter(file, datasync);
 222
 223         ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
 224         if (ret)
 225                 return ret;
 226         mutex_lock(&inode->i_mutex);
 227
 228         if (inode->i_sb->s_flags & MS_RDONLY)
 229                 goto out;
 230
 231         ret = ext4_flush_completed_IO(inode);
 232         if (ret < 0)
 233                 goto out;
 234
 235         if (!journal) {
 236                 ret = __sync_inode(inode, datasync);
 237                 if (!ret && !list_empty(&inode->i_dentry))
 238                         ret = ext4_sync_parent(inode);
 239                 goto out;
 240         }
 241
 242         /*
 243          * data=writeback,ordered:
 244          *  The caller's filemap_fdatawrite()/wait will sync the data.
 245          *  Metadata is in the journal, we wait for proper transaction to
 246          *  commit here.
 247          *
 248          * data=journal:
 249          *  filemap_fdatawrite won't do anything (the buffers are clean).
 250          *  ext4_force_commit will write the file data into the journal and
 251          *  will wait on that.
 252          *  filemap_fdatawait() will encounter a ton of newly-dirtied pages
 253          *  (they were dirtied by commit).  But that's OK - the blocks are
 254          *  safe in-journal, which is all fsync() needs to ensure.
 255          */
 256         if (ext4_should_journal_data(inode)) {
 257                 ret = ext4_force_commit(inode->i_sb);
 258                 goto out;
 259         }
 260
 261         commit_tid = datasync ? ei->i_datasync_tid : ei->i_sync_tid;
 262         if (journal->j_flags & JBD2_BARRIER &&
 263             !jbd2_trans_will_send_data_barrier(journal, commit_tid))
 264                 needs_barrier = true;
 265         jbd2_log_start_commit(journal, commit_tid);
 266         ret = jbd2_log_wait_commit(journal, commit_tid);
 267         if (needs_barrier)
 268                 blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
 269  out:
 270         mutex_unlock(&inode->i_mutex);
 271         trace_ext4_sync_file_exit(inode, ret);
 272         return ret;
 273 }