/*
 *  linux/fs/ext4/fsync.c
 *
 *  Copyright (C) 1993  Stephen Tweedie (sct@redhat.com)
 *  from
 *  Copyright (C) 1992  Remy Card (card@masi.ibp.fr)
 *                      Laboratoire MASI - Institut Blaise Pascal
 *                      Universite Pierre et Marie Curie (Paris VI)
 *  from
 *  linux/fs/minix/truncate.c   Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  ext4fs fsync primitive
 *
 *  Big-endian to little-endian byte-swapping/bitmaps by
 *        David S. Miller (davem@caip.rutgers.edu), 1995
 *
 *  Removed unnecessary code duplication for little endian machines
 *  and excessive __inline__s.
 *        Andi Kleen, 1997
 *
 * Major simplications and cleanup - we only need to do the metadata, because
 * we can depend on generic_block_fdatasync() to sync the data blocks.
 */

#include <linux/time.h>
#include <linux/fs.h>
#include <linux/sched.h>
#include <linux/writeback.h>
#include <linux/jbd2.h>
#include <linux/blkdev.h>

#include "ext4.h"
#include "ext4_jbd2.h"

#include <trace/events/ext4.h>

static void dump_completed_IO(struct inode * inode)
{
#ifdef  EXT4FS_DEBUG
        struct list_head *cur, *before, *after;
        ext4_io_end_t *io, *io0, *io1;
        unsigned long flags;

        if (list_empty(&EXT4_I(inode)->i_completed_io_list)){
                ext4_debug("inode %lu completed_io list is empty\n", inode->i_ino);
                return;
        }

        ext4_debug("Dump inode %lu completed_io list \n", inode->i_ino);
        spin_lock_irqsave(&EXT4_I(inode)->i_completed_io_lock, flags);
        list_for_each_entry(io, &EXT4_I(inode)->i_completed_io_list, list){
                cur = &io->list;
                before = cur->prev;
                io0 = container_of(before, ext4_io_end_t, list);
                after = cur->next;
                io1 = container_of(after, ext4_io_end_t, list);

                ext4_debug("io 0x%p from inode %lu,prev 0x%p,next 0x%p\n",
                            io, inode->i_ino, io0, io1);
        }
        spin_unlock_irqrestore(&EXT4_I(inode)->i_completed_io_lock, flags);
#endif
}

/*
 * This function is called from ext4_sync_file().
 *
 * When IO is completed, the work to convert unwritten extents to
 * written is queued on workqueue but may not get immediately
 * scheduled. When fsync is called, we need to ensure the
 * conversion is complete before fsync returns.
 * The inode keeps track of a list of pending/completed IO that
 * might needs to do the conversion. This function walks through
 * the list and convert the related unwritten extents for completed IO
 * to written.
 * The function return the number of pending IOs on success.
 */
int ext4_flush_completed_IO(struct inode *inode)
{
        ext4_io_end_t *io;
        struct ext4_inode_info *ei = EXT4_I(inode);
        unsigned long flags;
        int ret = 0;
        int ret2 = 0;

        dump_completed_IO(inode);
        spin_lock_irqsave(&ei->i_completed_io_lock, flags);
        while (!list_empty(&ei->i_completed_io_list)){
                io = list_entry(ei->i_completed_io_list.next,
                                ext4_io_end_t, list);
                list_del_init(&io->list);
                io->flag |= EXT4_IO_END_IN_FSYNC;
                /*
                 * Calling ext4_end_io_nolock() to convert completed
                 * IO to written.
                 *
                 * When ext4_sync_file() is called, run_queue() may already
                 * about to flush the work corresponding to this io structure.
                 * It will be upset if it founds the io structure related
                 * to the work-to-be schedule is freed.
                 *
                 * Thus we need to keep the io structure still valid here after
                 * conversion finished. The io structure has a flag to
                 * avoid double converting from both fsync and background work
                 * queue work.
                 */
                spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
                ret = ext4_end_io_nolock(io);
                if (ret < 0)
                        ret2 = ret;
                spin_lock_irqsave(&ei->i_completed_io_lock, flags);
                io->flag &= ~EXT4_IO_END_IN_FSYNC;
        }
        spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
        return (ret2 < 0) ? ret2 : 0;
}

/*
 * If we're not journaling and this is a just-created file, we have to
 * sync our parent directory (if it was freshly created) since
 * otherwise it will only be written by writeback, leaving a huge
 * window during which a crash may lose the file.  This may apply for
 * the parent directory's parent as well, and so on recursively, if
 * they are also freshly created.
 */
static int ext4_sync_parent(struct inode *inode)
{
        struct writeback_control wbc;
        struct dentry *dentry = NULL;
        struct inode *next;
        int ret = 0;

        if (!ext4_test_inode_state(inode, EXT4_STATE_NEWENTRY))
                return 0;
        inode = igrab(inode);
        while (ext4_test_inode_state(inode, EXT4_STATE_NEWENTRY)) {
                ext4_clear_inode_state(inode, EXT4_STATE_NEWENTRY);
                dentry = NULL;
                spin_lock(&inode->i_lock);
                if (!list_empty(&inode->i_dentry)) {
                        dentry = list_first_entry(&inode->i_dentry,
                                                  struct dentry, d_alias);
                        dget(dentry);
                }
                spin_unlock(&inode->i_lock);
                if (!dentry)
                        break;
                next = igrab(dentry->d_parent->d_inode);
                dput(dentry);
                if (!next)
                        break;
                iput(inode);
                inode = next;
                ret = sync_mapping_buffers(inode->i_mapping);
                if (ret)
                        break;
                memset(&wbc, 0, sizeof(wbc));
                wbc.sync_mode = WB_SYNC_ALL;
                wbc.nr_to_write = 0;         /* only write out the inode */
                ret = sync_inode(inode, &wbc);
                if (ret)
                        break;
        }
        iput(inode);
        return ret;
}

/**
 * __sync_file - generic_file_fsync without the locking and filemap_write
 * @inode:      inode to sync
 * @datasync:   only sync essential metadata if true
 *
 * This is just generic_file_fsync without the locking.  This is needed for
 * nojournal mode to make sure this inodes data/metadata makes it to disk
 * properly.  The i_mutex should be held already.
 */
static int __sync_inode(struct inode *inode, int datasync)
{
        int err;
        int ret;

        ret = sync_mapping_buffers(inode->i_mapping);
        if (!(inode->i_state & I_DIRTY))
                return ret;
        if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
                return ret;

        err = sync_inode_metadata(inode, 1);
        if (ret == 0)
                ret = err;
        return ret;
}

/*
 * akpm: A new design for ext4_sync_file().
 *
 * This is only called from sys_fsync(), sys_fdatasync() and sys_msync().
 * There cannot be a transaction open by this task.
 * Another task could have dirtied this inode.  Its data can be in any
 * state in the journalling system.
 *
 * What we do is just kick off a commit and wait on it.  This will snapshot the
 * inode to disk.
 *
 * i_mutex lock is held when entering and exiting this function
 */

int ext4_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
{
        struct inode *inode = file->f_mapping->host;
        struct ext4_inode_info *ei = EXT4_I(inode);
        journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
        int ret;
        tid_t commit_tid;
        bool needs_barrier = false;

        J_ASSERT(ext4_journal_current_handle() == NULL);

        trace_ext4_sync_file_enter(file, datasync);

        ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
        if (ret)
                return ret;
        mutex_lock(&inode->i_mutex);

        if (inode->i_sb->s_flags & MS_RDONLY)
                goto out;

        ret = ext4_flush_completed_IO(inode);
        if (ret < 0)
                goto out;

        if (!journal) {
                ret = __sync_inode(inode, datasync);
                if (!ret && !list_empty(&inode->i_dentry))
                        ret = ext4_sync_parent(inode);
                goto out;
        }

        /*
         * data=writeback,ordered:
         *  The caller's filemap_fdatawrite()/wait will sync the data.
         *  Metadata is in the journal, we wait for proper transaction to
         *  commit here.
         *
         * data=journal:
         *  filemap_fdatawrite won't do anything (the buffers are clean).
         *  ext4_force_commit will write the file data into the journal and
         *  will wait on that.
         *  filemap_fdatawait() will encounter a ton of newly-dirtied pages
         *  (they were dirtied by commit).  But that's OK - the blocks are
         *  safe in-journal, which is all fsync() needs to ensure.
         */
        if (ext4_should_journal_data(inode)) {
                ret = ext4_force_commit(inode->i_sb);
                goto out;
        }

        commit_tid = datasync ? ei->i_datasync_tid : ei->i_sync_tid;
        if (journal->j_flags & JBD2_BARRIER &&
            !jbd2_trans_will_send_data_barrier(journal, commit_tid))
                needs_barrier = true;
        jbd2_log_start_commit(journal, commit_tid);
        ret = jbd2_log_wait_commit(journal, commit_tid);
        if (needs_barrier)
                blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
 out:
        mutex_unlock(&inode->i_mutex);
        trace_ext4_sync_file_exit(inode, ret);
        return ret;
}