linux/fs/ext4/fsync.c
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   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
  37static 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 */
  78int 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 */
 126static 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 = d_find_any_alias(inode);
 139                if (!dentry)
 140                        break;
 141                next = igrab(dentry->d_parent->d_inode);
 142                dput(dentry);
 143                if (!next)
 144                        break;
 145                iput(inode);
 146                inode = next;
 147                ret = sync_mapping_buffers(inode->i_mapping);
 148                if (ret)
 149                        break;
 150                memset(&wbc, 0, sizeof(wbc));
 151                wbc.sync_mode = WB_SYNC_ALL;
 152                wbc.nr_to_write = 0;         /* only write out the inode */
 153                ret = sync_inode(inode, &wbc);
 154                if (ret)
 155                        break;
 156        }
 157        iput(inode);
 158        return ret;
 159}
 160
 161/**
 162 * __sync_file - generic_file_fsync without the locking and filemap_write
 163 * @inode:      inode to sync
 164 * @datasync:   only sync essential metadata if true
 165 *
 166 * This is just generic_file_fsync without the locking.  This is needed for
 167 * nojournal mode to make sure this inodes data/metadata makes it to disk
 168 * properly.  The i_mutex should be held already.
 169 */
 170static int __sync_inode(struct inode *inode, int datasync)
 171{
 172        int err;
 173        int ret;
 174
 175        ret = sync_mapping_buffers(inode->i_mapping);
 176        if (!(inode->i_state & I_DIRTY))
 177                return ret;
 178        if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
 179                return ret;
 180
 181        err = sync_inode_metadata(inode, 1);
 182        if (ret == 0)
 183                ret = err;
 184        return ret;
 185}
 186
 187/*
 188 * akpm: A new design for ext4_sync_file().
 189 *
 190 * This is only called from sys_fsync(), sys_fdatasync() and sys_msync().
 191 * There cannot be a transaction open by this task.
 192 * Another task could have dirtied this inode.  Its data can be in any
 193 * state in the journalling system.
 194 *
 195 * What we do is just kick off a commit and wait on it.  This will snapshot the
 196 * inode to disk.
 197 *
 198 * i_mutex lock is held when entering and exiting this function
 199 */
 200
 201int ext4_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
 202{
 203        struct inode *inode = file->f_mapping->host;
 204        struct ext4_inode_info *ei = EXT4_I(inode);
 205        journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
 206        int ret;
 207        tid_t commit_tid;
 208        bool needs_barrier = false;
 209
 210        J_ASSERT(ext4_journal_current_handle() == NULL);
 211
 212        trace_ext4_sync_file_enter(file, datasync);
 213
 214        ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
 215        if (ret)
 216                return ret;
 217        mutex_lock(&inode->i_mutex);
 218
 219        if (inode->i_sb->s_flags & MS_RDONLY)
 220                goto out;
 221
 222        ret = ext4_flush_completed_IO(inode);
 223        if (ret < 0)
 224                goto out;
 225
 226        if (!journal) {
 227                ret = __sync_inode(inode, datasync);
 228                if (!ret && !hlist_empty(&inode->i_dentry))
 229                        ret = ext4_sync_parent(inode);
 230                goto out;
 231        }
 232
 233        /*
 234         * data=writeback,ordered:
 235         *  The caller's filemap_fdatawrite()/wait will sync the data.
 236         *  Metadata is in the journal, we wait for proper transaction to
 237         *  commit here.
 238         *
 239         * data=journal:
 240         *  filemap_fdatawrite won't do anything (the buffers are clean).
 241         *  ext4_force_commit will write the file data into the journal and
 242         *  will wait on that.
 243         *  filemap_fdatawait() will encounter a ton of newly-dirtied pages
 244         *  (they were dirtied by commit).  But that's OK - the blocks are
 245         *  safe in-journal, which is all fsync() needs to ensure.
 246         */
 247        if (ext4_should_journal_data(inode)) {
 248                ret = ext4_force_commit(inode->i_sb);
 249                goto out;
 250        }
 251
 252        commit_tid = datasync ? ei->i_datasync_tid : ei->i_sync_tid;
 253        if (journal->j_flags & JBD2_BARRIER &&
 254            !jbd2_trans_will_send_data_barrier(journal, commit_tid))
 255                needs_barrier = true;
 256        jbd2_log_start_commit(journal, commit_tid);
 257        ret = jbd2_log_wait_commit(journal, commit_tid);
 258        if (needs_barrier)
 259                blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
 260 out:
 261        mutex_unlock(&inode->i_mutex);
 262        trace_ext4_sync_file_exit(inode, ret);
 263        return ret;
 264}
 265
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