linux/fs/ext4/fsync.c
Jan Kara 93628ffb9b ext4: fix waiting and sending of a barrier in ext4_sync_file()
jbd2_log_start_commit() returns 1 only when we really start a
transaction.  But we also need to wait for a transaction when the
commit is already running.  Fix this problem by waiting for
transaction commit unconditionally (which is just a quick check if the
transaction is already committed).

Also we have to be more careful with sending of a barrier because when
transaction is being committed in parallel to ext4_sync_file()
running, we cannot be sure that the barrier the journalling code sends
happens after we wrote all the data for fsync (note that not every
data writeout needs to trigger metadata changes thus commit of some
metadata changes can be running while other data is still written
out). So use jbd2_will_send_data_barrier() helper to detect the common
cases when we can be sure barrier will be issued by the commit code
and issue the barrier ourselves in the remaining cases.

Reported-by: Edward Goggin <egoggin@vmware.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2011-05-24 12:00:54 -04:00

226 lines
6.8 KiB
C

/*
* 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.
*/
extern 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;
if (list_empty(&ei->i_completed_io_list))
return ret;
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);
/*
* 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);
spin_lock_irqsave(&ei->i_completed_io_lock, flags);
if (ret < 0)
ret2 = ret;
else
list_del_init(&io->list);
}
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;
int ret = 0;
while (inode && ext4_test_inode_state(inode, EXT4_STATE_NEWENTRY)) {
ext4_clear_inode_state(inode, EXT4_STATE_NEWENTRY);
dentry = list_entry(inode->i_dentry.next,
struct dentry, d_alias);
if (!dentry || !dentry->d_parent || !dentry->d_parent->d_inode)
break;
inode = dentry->d_parent->d_inode;
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;
}
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, 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);
if (inode->i_sb->s_flags & MS_RDONLY)
return 0;
ret = ext4_flush_completed_IO(inode);
if (ret < 0)
goto out;
if (!journal) {
ret = generic_file_fsync(file, 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:
trace_ext4_sync_file_exit(inode, ret);
return ret;
}