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marcus.erl |
/*
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* linux/fs/ext4/fsync.c
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*
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* Copyright (C) 1993 Stephen Tweedie (sct@redhat.com)
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* from
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* Copyright (C) 1992 Remy Card (card@masi.ibp.fr)
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* Laboratoire MASI - Institut Blaise Pascal
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* Universite Pierre et Marie Curie (Paris VI)
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* from
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* linux/fs/minix/truncate.c Copyright (C) 1991, 1992 Linus Torvalds
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*
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* ext4fs fsync primitive
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*
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* Big-endian to little-endian byte-swapping/bitmaps by
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* David S. Miller (davem@caip.rutgers.edu), 1995
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*
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* Removed unnecessary code duplication for little endian machines
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* and excessive __inline__s.
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* Andi Kleen, 1997
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*
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* Major simplications and cleanup - we only need to do the metadata, because
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* we can depend on generic_block_fdatasync() to sync the data blocks.
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*/
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#include <linux/time.h>
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#include <linux/fs.h>
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#include <linux/sched.h>
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#include <linux/writeback.h>
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#include <linux/jbd2.h>
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#include <linux/ext4_fs.h>
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#include <linux/ext4_jbd2.h>
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/*
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* akpm: A new design for ext4_sync_file().
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*
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* This is only called from sys_fsync(), sys_fdatasync() and sys_msync().
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* There cannot be a transaction open by this task.
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* Another task could have dirtied this inode. Its data can be in any
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* state in the journalling system.
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*
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* What we do is just kick off a commit and wait on it. This will snapshot the
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* inode to disk.
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*/
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int ext4_sync_file(struct file * file, struct dentry *dentry, int datasync)
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{
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struct inode *inode = dentry->d_inode;
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int ret = 0;
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J_ASSERT(ext4_journal_current_handle() == NULL);
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/*
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* data=writeback:
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* The caller's filemap_fdatawrite()/wait will sync the data.
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* sync_inode() will sync the metadata
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*
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* data=ordered:
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* The caller's filemap_fdatawrite() will write the data and
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* sync_inode() will write the inode if it is dirty. Then the caller's
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* filemap_fdatawait() will wait on the pages.
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*
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* data=journal:
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* filemap_fdatawrite won't do anything (the buffers are clean).
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* ext4_force_commit will write the file data into the journal and
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* will wait on that.
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* filemap_fdatawait() will encounter a ton of newly-dirtied pages
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* (they were dirtied by commit). But that's OK - the blocks are
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* safe in-journal, which is all fsync() needs to ensure.
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*/
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if (ext4_should_journal_data(inode)) {
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ret = ext4_force_commit(inode->i_sb);
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goto out;
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}
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/*
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* The VFS has written the file data. If the inode is unaltered
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* then we need not start a commit.
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*/
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if (inode->i_state & (I_DIRTY_SYNC|I_DIRTY_DATASYNC)) {
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struct writeback_control wbc = {
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.sync_mode = WB_SYNC_ALL,
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.nr_to_write = 0, /* sys_fsync did this */
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};
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ret = sync_inode(inode, &wbc);
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}
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out:
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return ret;
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}
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