/* *  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/blkdev.h> #include "ext4.h"#include "ext4_jbd2.h" #include <trace/events/ext4.h> /* * 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 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 = d_find_any_alias(inode);		if (!dentry)			break;		next = igrab(d_inode(dentry->d_parent));		dput(dentry);		if (!next)			break;		iput(inode);		inode = next;		/*		 * The directory inode may have gone through rmdir by now. But		 * the inode itself and its blocks are still allocated (we hold		 * a reference to the inode so it didn't go through		 * ext4_evict_inode()) and so we are safe to flush metadata		 * blocks and the inode.		 */		ret = sync_mapping_buffers(inode->i_mapping);		if (ret)			break;		ret = sync_inode_metadata(inode, 1);		if (ret)			break;	}	iput(inode);	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. */ 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 = 0, err;	tid_t commit_tid;	bool needs_barrier = false; 	if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))		return -EIO; 	J_ASSERT(ext4_journal_current_handle() == NULL); 	trace_ext4_sync_file_enter(file, datasync); 	if (inode->i_sb->s_flags & MS_RDONLY) {		/* Make sure that we read updated s_mount_flags value */		smp_rmb();		if (EXT4_SB(inode->i_sb)->s_mount_flags & EXT4_MF_FS_ABORTED)			ret = -EROFS;		goto out;	} 	if (!journal) {		ret = __generic_file_fsync(file, start, end, datasync);		if (!ret)			ret = ext4_sync_parent(inode);		if (test_opt(inode->i_sb, BARRIER))			goto issue_flush;		goto out;	} 	ret = file_write_and_wait_range(file, start, end);	if (ret)		return ret;	/*	 * 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;	ret = jbd2_complete_transaction(journal, commit_tid);	if (needs_barrier) {	issue_flush:		err = blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);		if (!ret)			ret = err;	}out:	trace_ext4_sync_file_exit(inode, ret);	return ret;}