Patchwork [3/7] ext4: serialize dio nolocked reads with defrag workers V2

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Submitter Dmitri Monakho
Date Sept. 9, 2012, 5:27 p.m.
Message ID <1347211634-11509-4-git-send-email-dmonakhov@openvz.org>
Download mbox | patch
Permalink /patch/182638/
State Superseded
Headers show

Comments

Dmitri Monakho - Sept. 9, 2012, 5:27 p.m.
Inode's block defrag and ext4_change_inode_journal_flag() may
affect nonlocked DIO reads result, so proper synchronization
required.

- Add missed inode_dio_wait() calls where appropriate
- Check inode state under extra i_dio_count reference.

Changes from V1:
- add missed memory bariers
- move DIOREAD_LOCK state check out from generic should_dioread_nolock
  otherwise it will affect existing DIO readers.

Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
---
 fs/ext4/ext4.h        |    3 +++
 fs/ext4/indirect.c    |   23 +++++++++++++++++++++++
 fs/ext4/inode.c       |    4 ++++
 fs/ext4/move_extent.c |    5 +++++
 4 files changed, 35 insertions(+), 0 deletions(-)
Jan Kara - Sept. 10, 2012, 9:31 a.m.
On Sun 09-09-12 21:27:10, Dmitry Monakhov wrote:
> Inode's block defrag and ext4_change_inode_journal_flag() may
> affect nonlocked DIO reads result, so proper synchronization
> required.
> 
> - Add missed inode_dio_wait() calls where appropriate
> - Check inode state under extra i_dio_count reference.
> 
> Changes from V1:
> - add missed memory bariers
> - move DIOREAD_LOCK state check out from generic should_dioread_nolock
>   otherwise it will affect existing DIO readers.
  Looks good. Just maybe I would rename ext4_inode_dio_wait() to
ext4_inode_block_unlocked_dio(). Anyway you can add:
Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
> ---
>  fs/ext4/ext4.h        |    3 +++
>  fs/ext4/indirect.c    |   23 +++++++++++++++++++++++
>  fs/ext4/inode.c       |    4 ++++
>  fs/ext4/move_extent.c |    5 +++++
>  4 files changed, 35 insertions(+), 0 deletions(-)
> 
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index be976ca..0377d2b 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -1348,6 +1348,8 @@ enum {
>  	EXT4_STATE_DIO_UNWRITTEN,	/* need convert on dio done*/
>  	EXT4_STATE_NEWENTRY,		/* File just added to dir */
>  	EXT4_STATE_DELALLOC_RESERVED,	/* blks already reserved for delalloc */
> +	EXT4_STATE_DIOREAD_LOCK,	/* Disable support for dio read
> +					   nolocking */
>  };
>  
>  #define EXT4_INODE_BIT_FNS(name, field, offset)				\
> @@ -2015,6 +2017,7 @@ extern void ext4_da_update_reserve_space(struct inode *inode,
>  /* indirect.c */
>  extern int ext4_ind_map_blocks(handle_t *handle, struct inode *inode,
>  				struct ext4_map_blocks *map, int flags);
> +extern void ext4_inode_dio_wait(struct inode *inode, int resume);
>  extern ssize_t ext4_ind_direct_IO(int rw, struct kiocb *iocb,
>  				const struct iovec *iov, loff_t offset,
>  				unsigned long nr_segs);
> diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c
> index 61f13e5..3714413 100644
> --- a/fs/ext4/indirect.c
> +++ b/fs/ext4/indirect.c
> @@ -760,6 +760,19 @@ out:
>  	return err;
>  }
>  
> +/* Wait for existing dio workers
> + * Disable DIO read nolock optimization, so new dioreaders will
> + * be forced to grab i_mutex
> +*/
> +void ext4_inode_dio_wait(struct inode *inode, int resume_readers)
> +{
> +	ext4_set_inode_state(inode, EXT4_STATE_DIOREAD_LOCK);
> +	smp_mb();
> +	inode_dio_wait(inode);
> +	if (resume_readers)
> +		ext4_set_inode_state(inode, EXT4_STATE_DIOREAD_LOCK);
> +}
> +
>  /*
>   * O_DIRECT for ext3 (or indirect map) based files
>   *
> @@ -810,10 +823,20 @@ retry:
>  		if (unlikely(!list_empty(&ei->i_completed_io_list)))
>  			ext4_flush_completed_IO(inode);
>  
> +		/* Nolock dioread optimization may be dynamically disabled.
> +		 * Check inode's state while holding extra i_dio_count ref. */
> +		atomic_inc(&inode->i_dio_count);
> +		smp_mb();
> +		if (!unlikely(ext4_test_inode_state(inode,
> +						    EXT4_STATE_DIOREAD_LOCK))) {
> +			inode_dio_done(inode);
> +			goto retry;
> +		}
>  		ret = __blockdev_direct_IO(rw, iocb, inode,
>  				 inode->i_sb->s_bdev, iov,
>  				 offset, nr_segs,
>  				 ext4_get_block, NULL, NULL, 0);
> +		inode_dio_done(inode);
>  	} else {
>  		ret = blockdev_direct_IO(rw, iocb, inode, iov,
>  				 offset, nr_segs, ext4_get_block);
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 762b955..ffb4a27 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -4720,6 +4720,9 @@ int ext4_change_inode_journal_flag(struct inode *inode, int val)
>  			return err;
>  	}
>  
> +	/* Wait for all existing dio workers */
> +	ext4_inode_dio_wait(inode, 0);
> +
>  	jbd2_journal_lock_updates(journal);
>  
>  	/*
> @@ -4739,6 +4742,7 @@ int ext4_change_inode_journal_flag(struct inode *inode, int val)
>  	ext4_set_aops(inode);
>  
>  	jbd2_journal_unlock_updates(journal);
> +	ext4_clear_inode_state(inode, EXT4_STATE_DIOREAD_LOCK);
>  
>  	/* Finally we can mark the inode as dirty. */
>  
> diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
> index c5826c6..aea0e7a 100644
> --- a/fs/ext4/move_extent.c
> +++ b/fs/ext4/move_extent.c
> @@ -1214,6 +1214,9 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp,
>  	if (ret1 < 0)
>  		return ret1;
>  
> +	/* Wait for all existing dio workers */
> +	ext4_inode_dio_wait(orig_inode, 0);
> +	ext4_inode_dio_wait(donor_inode, 0);
>  	/* Protect extent tree against block allocations via delalloc */
>  	double_down_write_data_sem(orig_inode, donor_inode);
>  	/* Check the filesystem environment whether move_extent can be done */
> @@ -1412,6 +1415,8 @@ out:
>  		kfree(holecheck_path);
>  	}
>  	double_up_write_data_sem(orig_inode, donor_inode);
> +	ext4_clear_inode_state(orig_inode, EXT4_STATE_DIOREAD_LOCK);
> +	ext4_clear_inode_state(donor_inode, EXT4_STATE_DIOREAD_LOCK);
>  	ret2 = mext_inode_double_unlock(orig_inode, donor_inode);
>  
>  	if (ret1)
> -- 
> 1.7.7.6
>
Jan Kara - Sept. 10, 2012, 10 a.m.
On Mon 10-09-12 11:31:26, Jan Kara wrote:
> On Sun 09-09-12 21:27:10, Dmitry Monakhov wrote:
> > Inode's block defrag and ext4_change_inode_journal_flag() may
> > affect nonlocked DIO reads result, so proper synchronization
> > required.
> > 
> > - Add missed inode_dio_wait() calls where appropriate
> > - Check inode state under extra i_dio_count reference.
> > 
> > Changes from V1:
> > - add missed memory bariers
> > - move DIOREAD_LOCK state check out from generic should_dioread_nolock
> >   otherwise it will affect existing DIO readers.
>   Looks good. Just maybe I would rename ext4_inode_dio_wait() to
> ext4_inode_block_unlocked_dio(). Anyway you can add:
> Reviewed-by: Jan Kara <jack@suse.cz>
  Oh, I found one more thing:

> > +/* Wait for existing dio workers
> > + * Disable DIO read nolock optimization, so new dioreaders will
> > + * be forced to grab i_mutex
> > +*/
> > +void ext4_inode_dio_wait(struct inode *inode, int resume_readers)
> > +{
> > +	ext4_set_inode_state(inode, EXT4_STATE_DIOREAD_LOCK);
> > +	smp_mb();
> > +	inode_dio_wait(inode);
> > +	if (resume_readers)
> > +		ext4_set_inode_state(inode, EXT4_STATE_DIOREAD_LOCK);
> > +}
> > +
 I've just now noticed the resume_readers argument.
a) You probably meant to call ext4_clear_inode_state() when that argument
is set?
b) You need a smp_mb() before clearing DIOREAD_LOCK?
c) Please remove the resume_readers argument and make a separate function
from that. That new function could be called:
ext4_inode_unblock_unlocked_dio().

								Honza

> >  /*
> >   * O_DIRECT for ext3 (or indirect map) based files
> >   *
> > @@ -810,10 +823,20 @@ retry:
> >  		if (unlikely(!list_empty(&ei->i_completed_io_list)))
> >  			ext4_flush_completed_IO(inode);
> >  
> > +		/* Nolock dioread optimization may be dynamically disabled.
> > +		 * Check inode's state while holding extra i_dio_count ref. */
> > +		atomic_inc(&inode->i_dio_count);
> > +		smp_mb();
> > +		if (!unlikely(ext4_test_inode_state(inode,
> > +						    EXT4_STATE_DIOREAD_LOCK))) {
> > +			inode_dio_done(inode);
> > +			goto retry;
> > +		}
> >  		ret = __blockdev_direct_IO(rw, iocb, inode,
> >  				 inode->i_sb->s_bdev, iov,
> >  				 offset, nr_segs,
> >  				 ext4_get_block, NULL, NULL, 0);
> > +		inode_dio_done(inode);
> >  	} else {
> >  		ret = blockdev_direct_IO(rw, iocb, inode, iov,
> >  				 offset, nr_segs, ext4_get_block);
> > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> > index 762b955..ffb4a27 100644
> > --- a/fs/ext4/inode.c
> > +++ b/fs/ext4/inode.c
> > @@ -4720,6 +4720,9 @@ int ext4_change_inode_journal_flag(struct inode *inode, int val)
> >  			return err;
> >  	}
> >  
> > +	/* Wait for all existing dio workers */
> > +	ext4_inode_dio_wait(inode, 0);
> > +
> >  	jbd2_journal_lock_updates(journal);
> >  
> >  	/*
> > @@ -4739,6 +4742,7 @@ int ext4_change_inode_journal_flag(struct inode *inode, int val)
> >  	ext4_set_aops(inode);
> >  
> >  	jbd2_journal_unlock_updates(journal);
> > +	ext4_clear_inode_state(inode, EXT4_STATE_DIOREAD_LOCK);
> >  
> >  	/* Finally we can mark the inode as dirty. */
> >  
> > diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
> > index c5826c6..aea0e7a 100644
> > --- a/fs/ext4/move_extent.c
> > +++ b/fs/ext4/move_extent.c
> > @@ -1214,6 +1214,9 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp,
> >  	if (ret1 < 0)
> >  		return ret1;
> >  
> > +	/* Wait for all existing dio workers */
> > +	ext4_inode_dio_wait(orig_inode, 0);
> > +	ext4_inode_dio_wait(donor_inode, 0);
> >  	/* Protect extent tree against block allocations via delalloc */
> >  	double_down_write_data_sem(orig_inode, donor_inode);
> >  	/* Check the filesystem environment whether move_extent can be done */
> > @@ -1412,6 +1415,8 @@ out:
> >  		kfree(holecheck_path);
> >  	}
> >  	double_up_write_data_sem(orig_inode, donor_inode);
> > +	ext4_clear_inode_state(orig_inode, EXT4_STATE_DIOREAD_LOCK);
> > +	ext4_clear_inode_state(donor_inode, EXT4_STATE_DIOREAD_LOCK);
> >  	ret2 = mext_inode_double_unlock(orig_inode, donor_inode);
> >  
> >  	if (ret1)
> > -- 
> > 1.7.7.6
> > 
> -- 
> Jan Kara <jack@suse.cz>
> SUSE Labs, CR

Patch

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index be976ca..0377d2b 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1348,6 +1348,8 @@  enum {
 	EXT4_STATE_DIO_UNWRITTEN,	/* need convert on dio done*/
 	EXT4_STATE_NEWENTRY,		/* File just added to dir */
 	EXT4_STATE_DELALLOC_RESERVED,	/* blks already reserved for delalloc */
+	EXT4_STATE_DIOREAD_LOCK,	/* Disable support for dio read
+					   nolocking */
 };
 
 #define EXT4_INODE_BIT_FNS(name, field, offset)				\
@@ -2015,6 +2017,7 @@  extern void ext4_da_update_reserve_space(struct inode *inode,
 /* indirect.c */
 extern int ext4_ind_map_blocks(handle_t *handle, struct inode *inode,
 				struct ext4_map_blocks *map, int flags);
+extern void ext4_inode_dio_wait(struct inode *inode, int resume);
 extern ssize_t ext4_ind_direct_IO(int rw, struct kiocb *iocb,
 				const struct iovec *iov, loff_t offset,
 				unsigned long nr_segs);
diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c
index 61f13e5..3714413 100644
--- a/fs/ext4/indirect.c
+++ b/fs/ext4/indirect.c
@@ -760,6 +760,19 @@  out:
 	return err;
 }
 
+/* Wait for existing dio workers
+ * Disable DIO read nolock optimization, so new dioreaders will
+ * be forced to grab i_mutex
+*/
+void ext4_inode_dio_wait(struct inode *inode, int resume_readers)
+{
+	ext4_set_inode_state(inode, EXT4_STATE_DIOREAD_LOCK);
+	smp_mb();
+	inode_dio_wait(inode);
+	if (resume_readers)
+		ext4_set_inode_state(inode, EXT4_STATE_DIOREAD_LOCK);
+}
+
 /*
  * O_DIRECT for ext3 (or indirect map) based files
  *
@@ -810,10 +823,20 @@  retry:
 		if (unlikely(!list_empty(&ei->i_completed_io_list)))
 			ext4_flush_completed_IO(inode);
 
+		/* Nolock dioread optimization may be dynamically disabled.
+		 * Check inode's state while holding extra i_dio_count ref. */
+		atomic_inc(&inode->i_dio_count);
+		smp_mb();
+		if (!unlikely(ext4_test_inode_state(inode,
+						    EXT4_STATE_DIOREAD_LOCK))) {
+			inode_dio_done(inode);
+			goto retry;
+		}
 		ret = __blockdev_direct_IO(rw, iocb, inode,
 				 inode->i_sb->s_bdev, iov,
 				 offset, nr_segs,
 				 ext4_get_block, NULL, NULL, 0);
+		inode_dio_done(inode);
 	} else {
 		ret = blockdev_direct_IO(rw, iocb, inode, iov,
 				 offset, nr_segs, ext4_get_block);
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 762b955..ffb4a27 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4720,6 +4720,9 @@  int ext4_change_inode_journal_flag(struct inode *inode, int val)
 			return err;
 	}
 
+	/* Wait for all existing dio workers */
+	ext4_inode_dio_wait(inode, 0);
+
 	jbd2_journal_lock_updates(journal);
 
 	/*
@@ -4739,6 +4742,7 @@  int ext4_change_inode_journal_flag(struct inode *inode, int val)
 	ext4_set_aops(inode);
 
 	jbd2_journal_unlock_updates(journal);
+	ext4_clear_inode_state(inode, EXT4_STATE_DIOREAD_LOCK);
 
 	/* Finally we can mark the inode as dirty. */
 
diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
index c5826c6..aea0e7a 100644
--- a/fs/ext4/move_extent.c
+++ b/fs/ext4/move_extent.c
@@ -1214,6 +1214,9 @@  ext4_move_extents(struct file *o_filp, struct file *d_filp,
 	if (ret1 < 0)
 		return ret1;
 
+	/* Wait for all existing dio workers */
+	ext4_inode_dio_wait(orig_inode, 0);
+	ext4_inode_dio_wait(donor_inode, 0);
 	/* Protect extent tree against block allocations via delalloc */
 	double_down_write_data_sem(orig_inode, donor_inode);
 	/* Check the filesystem environment whether move_extent can be done */
@@ -1412,6 +1415,8 @@  out:
 		kfree(holecheck_path);
 	}
 	double_up_write_data_sem(orig_inode, donor_inode);
+	ext4_clear_inode_state(orig_inode, EXT4_STATE_DIOREAD_LOCK);
+	ext4_clear_inode_state(donor_inode, EXT4_STATE_DIOREAD_LOCK);
 	ret2 = mext_inode_double_unlock(orig_inode, donor_inode);
 
 	if (ret1)