[PATCH] nilfs2: improve the performance of fdatasync()

Discussion:

Andreas Rohner

2014-09-22 16:20:27 UTC

Support for fdatasync() has been implemented in NILFS2 for a long time,
but whenever the corresponding inode is dirty the implementation falls
back to a full-flegded sync(). Since every write operation has to update
the modification time of the file, the inode will almost always be dirty
and fdatasync() will fall back to sync() most of the time. But this
fallback is only necessary for a change of the file size and not for
a change of the various timestamps.

This patch adds a new flag NILFS_I_INODE_SYNC to differentiate between
those two situations.

* If it is set the file size was changed and a full sync is necessary.
* If it is not set then only the timestamps were updated and
fdatasync() can go ahead.

There is already a similar flag I_DIRTY_DATASYNC on the VFS layer with
the exact same semantics. Unfortunately it cannot be used directly,
because NILFS2 doesn't implement write_inode() and doesn't clear the VFS
flags when inodes are written out. So the VFS writeback thread can
clear I_DIRTY_DATASYNC at any time without notifying NILFS2. So
I_DIRTY_DATASYNC has to be mapped onto NILFS_I_INODE_SYNC in
nilfs_update_inode().

Signed-off-by: Andreas Rohner <andreas.rohner-***@public.gmane.org>
---
fs/nilfs2/inode.c | 12 +++++++-----
fs/nilfs2/nilfs.h | 13 +++++++++++--
fs/nilfs2/segment.c | 3 ++-
3 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/fs/nilfs2/inode.c b/fs/nilfs2/inode.c
index 6252b17..2f67153 100644
--- a/fs/nilfs2/inode.c
+++ b/fs/nilfs2/inode.c
@@ -125,7 +125,7 @@ int nilfs_get_block(struct inode *inode, sector_t blkoff,
nilfs_transaction_abort(inode->i_sb);
goto out;
}
- nilfs_mark_inode_dirty(inode);
+ nilfs_mark_inode_dirty_sync(inode);
nilfs_transaction_commit(inode->i_sb); /* never fails */
/* Error handling should be detailed */
set_buffer_new(bh_result);
@@ -667,7 +667,7 @@ void nilfs_write_inode_common(struct inode *inode,
for substitutions of appended fields */
}

-void nilfs_update_inode(struct inode *inode, struct buffer_head *ibh)
+void nilfs_update_inode(struct inode *inode, struct buffer_head *ibh, int flags)
{
ino_t ino = inode->i_ino;
struct nilfs_inode_info *ii = NILFS_I(inode);
@@ -679,6 +679,8 @@ void nilfs_update_inode(struct inode *inode, struct buffer_head *ibh)
if (test_and_clear_bit(NILFS_I_NEW, &ii->i_state))
memset(raw_inode, 0, NILFS_MDT(ifile)->mi_entry_size);
set_bit(NILFS_I_INODE_DIRTY, &ii->i_state);
+ if (flags & I_DIRTY_DATASYNC)
+ set_bit(NILFS_I_INODE_SYNC, &ii->i_state);

nilfs_write_inode_common(inode, raw_inode, 0);
/* XXX: call with has_bmap = 0 is a workaround to avoid
@@ -934,7 +936,7 @@ int nilfs_set_file_dirty(struct inode *inode, unsigned nr_dirty)
return 0;
}

-int nilfs_mark_inode_dirty(struct inode *inode)
+int __nilfs_mark_inode_dirty(struct inode *inode, int flags)
{
struct buffer_head *ibh;
int err;
@@ -945,7 +947,7 @@ int nilfs_mark_inode_dirty(struct inode *inode)
"failed to reget inode block.\n");
return err;
}
- nilfs_update_inode(inode, ibh);
+ nilfs_update_inode(inode, ibh, flags);
mark_buffer_dirty(ibh);
nilfs_mdt_mark_dirty(NILFS_I(inode)->i_root->ifile);
brelse(ibh);
@@ -978,7 +980,7 @@ void nilfs_dirty_inode(struct inode *inode, int flags)
return;
}
nilfs_transaction_begin(inode->i_sb, &ti, 0);
- nilfs_mark_inode_dirty(inode);
+ __nilfs_mark_inode_dirty(inode, flags);
nilfs_transaction_commit(inode->i_sb); /* never fails */
}

diff --git a/fs/nilfs2/nilfs.h b/fs/nilfs2/nilfs.h
index 0696161..30573d7 100644
--- a/fs/nilfs2/nilfs.h
+++ b/fs/nilfs2/nilfs.h
@@ -107,6 +107,7 @@ enum {
NILFS_I_INODE_DIRTY, /* write_inode is requested */
NILFS_I_BMAP, /* has bmap and btnode_cache */
NILFS_I_GCINODE, /* inode for GC, on memory only */
+ NILFS_I_INODE_SYNC, /* dsync is not allowed for inode */
};

/*
@@ -273,7 +274,7 @@ struct inode *nilfs_iget(struct super_block *sb, struct nilfs_root *root,
unsigned long ino);
extern struct inode *nilfs_iget_for_gc(struct super_block *sb,
unsigned long ino, __u64 cno);
-extern void nilfs_update_inode(struct inode *, struct buffer_head *);
+extern void nilfs_update_inode(struct inode *, struct buffer_head *, int);
extern void nilfs_truncate(struct inode *);
extern void nilfs_evict_inode(struct inode *);
extern int nilfs_setattr(struct dentry *, struct iattr *);
@@ -282,10 +283,18 @@ int nilfs_permission(struct inode *inode, int mask);
int nilfs_load_inode_block(struct inode *inode, struct buffer_head **pbh);
extern int nilfs_inode_dirty(struct inode *);
int nilfs_set_file_dirty(struct inode *inode, unsigned nr_dirty);
-extern int nilfs_mark_inode_dirty(struct inode *);
+extern int __nilfs_mark_inode_dirty(struct inode *, int);
extern void nilfs_dirty_inode(struct inode *, int flags);
int nilfs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
__u64 start, __u64 len);
+static inline int nilfs_mark_inode_dirty(struct inode *inode)
+{
+ return __nilfs_mark_inode_dirty(inode, I_DIRTY);
+}
+static inline int nilfs_mark_inode_dirty_sync(struct inode *inode)
+{
+ return __nilfs_mark_inode_dirty(inode, I_DIRTY_SYNC);
+}

/* super.c */
extern struct inode *nilfs_alloc_inode(struct super_block *);
diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c
index a1a1916..6102f3e 100644
--- a/fs/nilfs2/segment.c
+++ b/fs/nilfs2/segment.c
@@ -931,6 +931,7 @@ static void nilfs_drop_collected_inodes(struct list_head *head)
continue;

clear_bit(NILFS_I_INODE_DIRTY, &ii->i_state);
+ clear_bit(NILFS_I_INODE_SYNC, &ii->i_state);
set_bit(NILFS_I_UPDATED, &ii->i_state);
}
}
@@ -2194,7 +2195,7 @@ int nilfs_construct_dsync_segment(struct super_block *sb, struct inode *inode,
nilfs_transaction_lock(sb, &ti, 0);

ii = NILFS_I(inode);
- if (test_bit(NILFS_I_INODE_DIRTY, &ii->i_state) ||
+ if (test_bit(NILFS_I_INODE_SYNC, &ii->i_state) ||
nilfs_test_opt(nilfs, STRICT_ORDER) ||
test_bit(NILFS_SC_UNCLOSED, &sci->sc_flags) ||
nilfs_discontinued(nilfs)) {

--
2.1.0

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Ryusuke Konishi

2014-09-23 05:09:55 UTC

Permalink

Hi Andreas,

Post by Andreas Rohner
Support for fdatasync() has been implemented in NILFS2 for a long time,
but whenever the corresponding inode is dirty the implementation falls
back to a full-flegded sync(). Since every write operation has to update
the modification time of the file, the inode will almost always be dirty
and fdatasync() will fall back to sync() most of the time. But this
fallback is only necessary for a change of the file size and not for
a change of the various timestamps.
This patch adds a new flag NILFS_I_INODE_SYNC to differentiate between
those two situations.
* If it is set the file size was changed and a full sync is necessary.
* If it is not set then only the timestamps were updated and
fdatasync() can go ahead.
There is already a similar flag I_DIRTY_DATASYNC on the VFS layer with
the exact same semantics. Unfortunately it cannot be used directly,
because NILFS2 doesn't implement write_inode() and doesn't clear the VFS
flags when inodes are written out. So the VFS writeback thread can
clear I_DIRTY_DATASYNC at any time without notifying NILFS2. So
I_DIRTY_DATASYNC has to be mapped onto NILFS_I_INODE_SYNC in
nilfs_update_inode().

I looked into the patch.

Very nice. This is what we should have done several years ago.

When this patch is applied, NILFS_I_INODE_DIRTY flag will be no longer
required. Can you remove it at the same time?

Thanks,
Ryusuke Konishi

Post by Andreas Rohner
---
fs/nilfs2/inode.c | 12 +++++++-----
fs/nilfs2/nilfs.h | 13 +++++++++++--
fs/nilfs2/segment.c | 3 ++-
3 files changed, 20 insertions(+), 8 deletions(-)
diff --git a/fs/nilfs2/inode.c b/fs/nilfs2/inode.c
index 6252b17..2f67153 100644
--- a/fs/nilfs2/inode.c
+++ b/fs/nilfs2/inode.c
@@ -125,7 +125,7 @@ int nilfs_get_block(struct inode *inode, sector_t blkoff,
nilfs_transaction_abort(inode->i_sb);
goto out;
}
- nilfs_mark_inode_dirty(inode);
+ nilfs_mark_inode_dirty_sync(inode);
nilfs_transaction_commit(inode->i_sb); /* never fails */
/* Error handling should be detailed */
set_buffer_new(bh_result);
@@ -667,7 +667,7 @@ void nilfs_write_inode_common(struct inode *inode,
for substitutions of appended fields */
}
-void nilfs_update_inode(struct inode *inode, struct buffer_head *ibh)
+void nilfs_update_inode(struct inode *inode, struct buffer_head *ibh, int flags)
{
ino_t ino = inode->i_ino;
struct nilfs_inode_info *ii = NILFS_I(inode);
@@ -679,6 +679,8 @@ void nilfs_update_inode(struct inode *inode, struct buffer_head *ibh)
if (test_and_clear_bit(NILFS_I_NEW, &ii->i_state))
memset(raw_inode, 0, NILFS_MDT(ifile)->mi_entry_size);
set_bit(NILFS_I_INODE_DIRTY, &ii->i_state);
+ if (flags & I_DIRTY_DATASYNC)
+ set_bit(NILFS_I_INODE_SYNC, &ii->i_state);
nilfs_write_inode_common(inode, raw_inode, 0);
/* XXX: call with has_bmap = 0 is a workaround to avoid
@@ -934,7 +936,7 @@ int nilfs_set_file_dirty(struct inode *inode, unsigned nr_dirty)
return 0;
}
-int nilfs_mark_inode_dirty(struct inode *inode)
+int __nilfs_mark_inode_dirty(struct inode *inode, int flags)
{
struct buffer_head *ibh;
int err;
@@ -945,7 +947,7 @@ int nilfs_mark_inode_dirty(struct inode *inode)
"failed to reget inode block.\n");
return err;
}
- nilfs_update_inode(inode, ibh);
+ nilfs_update_inode(inode, ibh, flags);
mark_buffer_dirty(ibh);
nilfs_mdt_mark_dirty(NILFS_I(inode)->i_root->ifile);
brelse(ibh);
@@ -978,7 +980,7 @@ void nilfs_dirty_inode(struct inode *inode, int flags)
return;
}
nilfs_transaction_begin(inode->i_sb, &ti, 0);
- nilfs_mark_inode_dirty(inode);
+ __nilfs_mark_inode_dirty(inode, flags);
nilfs_transaction_commit(inode->i_sb); /* never fails */
}
diff --git a/fs/nilfs2/nilfs.h b/fs/nilfs2/nilfs.h
index 0696161..30573d7 100644
--- a/fs/nilfs2/nilfs.h
+++ b/fs/nilfs2/nilfs.h
@@ -107,6 +107,7 @@ enum {
NILFS_I_INODE_DIRTY, /* write_inode is requested */
NILFS_I_BMAP, /* has bmap and btnode_cache */
NILFS_I_GCINODE, /* inode for GC, on memory only */
+ NILFS_I_INODE_SYNC, /* dsync is not allowed for inode */
};
/*
@@ -273,7 +274,7 @@ struct inode *nilfs_iget(struct super_block *sb, struct nilfs_root *root,
unsigned long ino);
extern struct inode *nilfs_iget_for_gc(struct super_block *sb,
unsigned long ino, __u64 cno);
-extern void nilfs_update_inode(struct inode *, struct buffer_head *);
+extern void nilfs_update_inode(struct inode *, struct buffer_head *, int);
extern void nilfs_truncate(struct inode *);
extern void nilfs_evict_inode(struct inode *);
extern int nilfs_setattr(struct dentry *, struct iattr *);
@@ -282,10 +283,18 @@ int nilfs_permission(struct inode *inode, int mask);
int nilfs_load_inode_block(struct inode *inode, struct buffer_head **pbh);
extern int nilfs_inode_dirty(struct inode *);
int nilfs_set_file_dirty(struct inode *inode, unsigned nr_dirty);
-extern int nilfs_mark_inode_dirty(struct inode *);
+extern int __nilfs_mark_inode_dirty(struct inode *, int);
extern void nilfs_dirty_inode(struct inode *, int flags);
int nilfs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
__u64 start, __u64 len);
+static inline int nilfs_mark_inode_dirty(struct inode *inode)
+{
+ return __nilfs_mark_inode_dirty(inode, I_DIRTY);
+}
+static inline int nilfs_mark_inode_dirty_sync(struct inode *inode)
+{
+ return __nilfs_mark_inode_dirty(inode, I_DIRTY_SYNC);
+}
/* super.c */
extern struct inode *nilfs_alloc_inode(struct super_block *);
diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c
index a1a1916..6102f3e 100644
--- a/fs/nilfs2/segment.c
+++ b/fs/nilfs2/segment.c
@@ -931,6 +931,7 @@ static void nilfs_drop_collected_inodes(struct list_head *head)
continue;
clear_bit(NILFS_I_INODE_DIRTY, &ii->i_state);
+ clear_bit(NILFS_I_INODE_SYNC, &ii->i_state);
set_bit(NILFS_I_UPDATED, &ii->i_state);
}
}
@@ -2194,7 +2195,7 @@ int nilfs_construct_dsync_segment(struct super_block *sb, struct inode *inode,
nilfs_transaction_lock(sb, &ti, 0);
ii = NILFS_I(inode);
- if (test_bit(NILFS_I_INODE_DIRTY, &ii->i_state) ||
+ if (test_bit(NILFS_I_INODE_SYNC, &ii->i_state) ||
nilfs_test_opt(nilfs, STRICT_ORDER) ||
test_bit(NILFS_SC_UNCLOSED, &sci->sc_flags) ||
nilfs_discontinued(nilfs)) {
--
2.1.0
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Andreas Rohner

2014-09-23 06:36:38 UTC

Permalink

Post by Ryusuke Konishi
Hi Andreas,

I looked into the patch.
Very nice. This is what we should have done several years ago.
When this patch is applied, NILFS_I_INODE_DIRTY flag will be no longer
required. Can you remove it at the same time?

Ah yes of course. I just assumed that NILFS_I_INODE_DIRTY is needed for
something else and never actually checked it. In that case don't you
think that NILFS_I_INODE_DIRTY is a better name for the flag than
NILFS_I_INODE_SYNC?

The SYNC can be a bit confusing, especially because I used it in the
helper functions, where it means exactly the opposite:

static inline int nilfs_mark_inode_dirty(struct inode *inode)
static inline int nilfs_mark_inode_dirty_sync(struct inode *inode)

I did that to match the corresponding names of the VFS functions:

static inline void mark_inode_dirty(struct inode *inode)
static inline void mark_inode_dirty_sync(struct inode *inode)

So there is a bit of a conflict in names. What do you think?

br,
Andreas Rohner

Post by Ryusuke Konishi
Thanks,
Ryusuke Konishi

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Ryusuke Konishi

2014-09-23 07:45:05 UTC

Permalink

Post by Andreas Rohner

Post by Ryusuke Konishi
Hi Andreas,

I looked into the patch.
Very nice. This is what we should have done several years ago.
When this patch is applied, NILFS_I_INODE_DIRTY flag will be no longer
required. Can you remove it at the same time?

Uum, I feel NILFS_I_INODE_DIRTY should not be reused since it now
means something more than the inode is dirty.

Post by Andreas Rohner
The SYNC can be a bit confusing, especially because I used it in the

Post by Ryusuke Konishi
+ if (flags & I_DIRTY_DATASYNC)
+ set_bit(NILFS_I_INODE_SYNC, &ii->i_state);

The new flag means that the inode is dirty and needs full sync for
fdatasync(). I don't have any good ideas for now.

Post by Andreas Rohner
static inline int nilfs_mark_inode_dirty(struct inode *inode)
static inline int nilfs_mark_inode_dirty_sync(struct inode *inode)
static inline void mark_inode_dirty(struct inode *inode)
static inline void mark_inode_dirty_sync(struct inode *inode)
So there is a bit of a conflict in names. What do you think?

I think we have no choice for this.

Regards,
Ryusuke Konishi

Post by Andreas Rohner
br,
Andreas Rohner

Post by Ryusuke Konishi
Thanks,
Ryusuke Konishi

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