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