Message-ID: <20131226154918.3040.92826.stgit@dhcp-10-30-28-216.sw.ru>
Date:	Thu, 26 Dec 2013 19:51:11 +0400
From:	Maxim Patlasov <MPatlasov@...allels.com>
To:	miklos@...redi.hu
Cc:	dev@...allels.com, xemul@...allels.com,
	fuse-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	jbottomley@...allels.com, linux-fsdevel@...r.kernel.org,
	akpm@...ux-foundation.org, fengguang.wu@...el.com, devel@...nvz.org
Subject: [PATCH 05/11] fuse: Trust kernel i_mtime only -v3

Let the kernel maintain i_mtime locally:
 - clear S_NOCMTIME
 - implement i_op->update_time()
 - flush mtime on fsync and last close
 - update i_mtime explicitly on truncate and fallocate

Fuse inode flag FUSE_I_MTIME_DIRTY serves as indication that local i_mtime
should be flushed to the server eventually.

Changed in v2 (thanks to Brian):
 - renamed FUSE_I_MTIME_UPDATED to FUSE_I_MTIME_DIRTY
 - simplified fuse_set_mtime_local()
 - abandoned optimizations: clearing the flag on some operations (like
   direct write) is doable, but may lead to unexpected changes of
   user-visible mtime.

Changed in v3 (thanks to Miklos):
 - let client fs know about local mtime change for ATTR_SIZE and
   !ATTR_MTIME_SET cases.

Signed-off-by: Maxim Patlasov <MPatlasov@...allels.com>
---
 fs/fuse/dir.c    |  113 +++++++++++++++++++++++++++++++++++++++++++++---------
 fs/fuse/file.c   |   30 ++++++++++++--
 fs/fuse/fuse_i.h |    6 ++-
 fs/fuse/inode.c  |   13 +++++-
 4 files changed, 136 insertions(+), 26 deletions(-)

diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index f022968..d1a3167 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -857,8 +857,11 @@ static void fuse_fillattr(struct inode *inode, struct fuse_attr *attr,
 	struct fuse_conn *fc = get_fuse_conn(inode);
 
 	/* see the comment in fuse_change_attributes() */
-	if (fc->writeback_cache && S_ISREG(inode->i_mode))
+	if (fc->writeback_cache && S_ISREG(inode->i_mode)) {
 		attr->size = i_size_read(inode);
+		attr->mtime = inode->i_mtime.tv_sec;
+		attr->mtimensec = inode->i_mtime.tv_nsec;
+	}
 
 	stat->dev = inode->i_sb->s_dev;
 	stat->ino = attr->ino;
@@ -1510,7 +1513,8 @@ static bool update_mtime(unsigned ivalid)
 	return true;
 }
 
-static void iattr_to_fattr(struct iattr *iattr, struct fuse_setattr_in *arg)
+static void iattr_to_fattr(struct iattr *iattr, struct fuse_setattr_in *arg,
+			   bool trust_local_mtime, struct timespec *mtime)
 {
 	unsigned ivalid = iattr->ia_valid;
 
@@ -1529,11 +1533,17 @@ static void iattr_to_fattr(struct iattr *iattr, struct fuse_setattr_in *arg)
 		if (!(ivalid & ATTR_ATIME_SET))
 			arg->valid |= FATTR_ATIME_NOW;
 	}
-	if ((ivalid & ATTR_MTIME) && update_mtime(ivalid)) {
+
+	if (!trust_local_mtime || (ivalid & ATTR_MTIME_SET) ||
+	    !(ivalid & ATTR_SIZE))
+		*mtime = iattr->ia_mtime;
+
+	if ((ivalid & ATTR_MTIME) && (update_mtime(ivalid) ||
+				      trust_local_mtime)) {
 		arg->valid |= FATTR_MTIME;
-		arg->mtime = iattr->ia_mtime.tv_sec;
-		arg->mtimensec = iattr->ia_mtime.tv_nsec;
-		if (!(ivalid & ATTR_MTIME_SET))
+		arg->mtime = mtime->tv_sec;
+		arg->mtimensec = mtime->tv_nsec;
+		if (!(ivalid & ATTR_MTIME_SET) && !trust_local_mtime)
 			arg->valid |= FATTR_MTIME_NOW;
 	}
 }
@@ -1582,6 +1592,63 @@ void fuse_release_nowrite(struct inode *inode)
 	spin_unlock(&fc->lock);
 }
 
+static void fuse_setattr_fill(struct fuse_conn *fc, struct fuse_req *req,
+			      struct inode *inode,
+			      struct fuse_setattr_in *inarg_p,
+			      struct fuse_attr_out *outarg_p)
+{
+	req->in.h.opcode = FUSE_SETATTR;
+	req->in.h.nodeid = get_node_id(inode);
+	req->in.numargs = 1;
+	req->in.args[0].size = sizeof(*inarg_p);
+	req->in.args[0].value = inarg_p;
+	req->out.numargs = 1;
+	if (fc->minor < 9)
+		req->out.args[0].size = FUSE_COMPAT_ATTR_OUT_SIZE;
+	else
+		req->out.args[0].size = sizeof(*outarg_p);
+	req->out.args[0].value = outarg_p;
+}
+
+/*
+ * Flush inode->i_mtime to the server
+ */
+int fuse_flush_mtime(struct file *file, bool nofail)
+{
+	struct inode *inode = file->f_mapping->host;
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_req *req = NULL;
+	struct fuse_setattr_in inarg;
+	struct fuse_attr_out outarg;
+	int err;
+
+	if (nofail) {
+		req = fuse_get_req_nofail_nopages(fc, file);
+	} else {
+		req = fuse_get_req_nopages(fc);
+		if (IS_ERR(req))
+			return PTR_ERR(req);
+	}
+
+	memset(&inarg, 0, sizeof(inarg));
+	memset(&outarg, 0, sizeof(outarg));
+
+	inarg.valid |= FATTR_MTIME;
+	inarg.mtime = inode->i_mtime.tv_sec;
+	inarg.mtimensec = inode->i_mtime.tv_nsec;
+
+	fuse_setattr_fill(fc, req, inode, &inarg, &outarg);
+	fuse_request_send(fc, req);
+	err = req->out.h.error;
+	fuse_put_request(fc, req);
+
+	if (!err)
+		clear_bit(FUSE_I_MTIME_DIRTY, &fi->state);
+
+	return err;
+}
+
 /*
  * Set attributes, and at the same time refresh them.
  *
@@ -1602,6 +1669,8 @@ int fuse_do_setattr(struct inode *inode, struct iattr *attr,
 	bool is_wb = fc->writeback_cache;
 	loff_t oldsize;
 	int err;
+	bool trust_local_mtime = is_wb && S_ISREG(inode->i_mode);
+	struct timespec new_mtime = current_fs_time(inode->i_sb);
 
 	if (!(fc->flags & FUSE_DEFAULT_PERMISSIONS))
 		attr->ia_valid |= ATTR_FORCE;
@@ -1630,7 +1699,7 @@ int fuse_do_setattr(struct inode *inode, struct iattr *attr,
 
 	memset(&inarg, 0, sizeof(inarg));
 	memset(&outarg, 0, sizeof(outarg));
-	iattr_to_fattr(attr, &inarg);
+	iattr_to_fattr(attr, &inarg, trust_local_mtime, &new_mtime);
 	if (file) {
 		struct fuse_file *ff = file->private_data;
 		inarg.valid |= FATTR_FH;
@@ -1641,17 +1710,7 @@ int fuse_do_setattr(struct inode *inode, struct iattr *attr,
 		inarg.valid |= FATTR_LOCKOWNER;
 		inarg.lock_owner = fuse_lock_owner_id(fc, current->files);
 	}
-	req->in.h.opcode = FUSE_SETATTR;
-	req->in.h.nodeid = get_node_id(inode);
-	req->in.numargs = 1;
-	req->in.args[0].size = sizeof(inarg);
-	req->in.args[0].value = &inarg;
-	req->out.numargs = 1;
-	if (fc->minor < 9)
-		req->out.args[0].size = FUSE_COMPAT_ATTR_OUT_SIZE;
-	else
-		req->out.args[0].size = sizeof(outarg);
-	req->out.args[0].value = &outarg;
+	fuse_setattr_fill(fc, req, inode, &inarg, &outarg);
 	fuse_request_send(fc, req);
 	err = req->out.h.error;
 	fuse_put_request(fc, req);
@@ -1668,6 +1727,12 @@ int fuse_do_setattr(struct inode *inode, struct iattr *attr,
 	}
 
 	spin_lock(&fc->lock);
+	/* the kernel maintains i_mtime locally */
+	if (trust_local_mtime && (attr->ia_valid & ATTR_MTIME)) {
+		inode->i_mtime = new_mtime;
+		clear_bit(FUSE_I_MTIME_DIRTY, &fi->state);
+	}
+
 	fuse_change_attributes_common(inode, &outarg.attr,
 				      attr_timeout(&outarg));
 	oldsize = inode->i_size;
@@ -1898,6 +1963,17 @@ static int fuse_removexattr(struct dentry *entry, const char *name)
 	return err;
 }
 
+static int fuse_update_time(struct inode *inode, struct timespec *now,
+			    int flags)
+{
+	if (flags & S_MTIME) {
+		inode->i_mtime = *now;
+		set_bit(FUSE_I_MTIME_DIRTY, &get_fuse_inode(inode)->state);
+		BUG_ON(!S_ISREG(inode->i_mode));
+	}
+	return 0;
+}
+
 static const struct inode_operations fuse_dir_inode_operations = {
 	.lookup		= fuse_lookup,
 	.mkdir		= fuse_mkdir,
@@ -1937,6 +2013,7 @@ static const struct inode_operations fuse_common_inode_operations = {
 	.getxattr	= fuse_getxattr,
 	.listxattr	= fuse_listxattr,
 	.removexattr	= fuse_removexattr,
+	.update_time	= fuse_update_time,
 };
 
 static const struct inode_operations fuse_symlink_inode_operations = {
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 333a764..eabe202 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -291,6 +291,9 @@ static int fuse_open(struct inode *inode, struct file *file)
 
 static int fuse_release(struct inode *inode, struct file *file)
 {
+	if (test_bit(FUSE_I_MTIME_DIRTY, &get_fuse_inode(inode)->state))
+		fuse_flush_mtime(file, true);
+
 	fuse_release_common(file, FUSE_RELEASE);
 
 	/* return value is ignored by VFS */
@@ -458,6 +461,12 @@ int fuse_fsync_common(struct file *file, loff_t start, loff_t end,
 
 	fuse_sync_writes(inode);
 
+	if (test_bit(FUSE_I_MTIME_DIRTY, &get_fuse_inode(inode)->state)) {
+		int err = fuse_flush_mtime(file, false);
+		if (err)
+			goto out;
+	}
+
 	req = fuse_get_req_nopages(fc);
 	if (IS_ERR(req)) {
 		err = PTR_ERR(req);
@@ -948,16 +957,21 @@ static size_t fuse_send_write(struct fuse_req *req, struct fuse_io_priv *io,
 	return req->misc.write.out.size;
 }
 
-void fuse_write_update_size(struct inode *inode, loff_t pos)
+bool fuse_write_update_size(struct inode *inode, loff_t pos)
 {
 	struct fuse_conn *fc = get_fuse_conn(inode);
 	struct fuse_inode *fi = get_fuse_inode(inode);
+	bool ret = false;
 
 	spin_lock(&fc->lock);
 	fi->attr_version = ++fc->attr_version;
-	if (pos > inode->i_size)
+	if (pos > inode->i_size) {
 		i_size_write(inode, pos);
+		ret = true;
+	}
 	spin_unlock(&fc->lock);
+
+	return ret;
 }
 
 static size_t fuse_send_write_pages(struct fuse_req *req, struct file *file,
@@ -2862,8 +2876,16 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset,
 		goto out;
 
 	/* we could have extended the file */
-	if (!(mode & FALLOC_FL_KEEP_SIZE))
-		fuse_write_update_size(inode, offset + length);
+	if (!(mode & FALLOC_FL_KEEP_SIZE)) {
+		bool changed = fuse_write_update_size(inode, offset + length);
+
+		if (changed && fc->writeback_cache) {
+			struct fuse_inode *fi = get_fuse_inode(inode);
+
+			inode->i_mtime = current_fs_time(inode->i_sb);
+			set_bit(FUSE_I_MTIME_DIRTY, &fi->state);
+		}
+	}
 
 	if (mode & FALLOC_FL_PUNCH_HOLE)
 		truncate_pagecache_range(inode, offset, offset + length - 1);
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index a490ba3..3028b8a 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -117,6 +117,8 @@ enum {
 	FUSE_I_ADVISE_RDPLUS,
 	/** An operation changing file size is in progress  */
 	FUSE_I_SIZE_UNSTABLE,
+	/** i_mtime has been updated locally; a flush to userspace needed */
+	FUSE_I_MTIME_DIRTY,
 };
 
 struct fuse_conn;
@@ -870,7 +872,9 @@ long fuse_ioctl_common(struct file *file, unsigned int cmd,
 unsigned fuse_file_poll(struct file *file, poll_table *wait);
 int fuse_dev_release(struct inode *inode, struct file *file);
 
-void fuse_write_update_size(struct inode *inode, loff_t pos);
+bool fuse_write_update_size(struct inode *inode, loff_t pos);
+
+int fuse_flush_mtime(struct file *file, bool nofail);
 
 int fuse_do_setattr(struct inode *inode, struct iattr *attr,
 		    struct file *file);
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 63818ab..253701f 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -170,8 +170,11 @@ void fuse_change_attributes_common(struct inode *inode, struct fuse_attr *attr,
 	inode->i_blocks  = attr->blocks;
 	inode->i_atime.tv_sec   = attr->atime;
 	inode->i_atime.tv_nsec  = attr->atimensec;
-	inode->i_mtime.tv_sec   = attr->mtime;
-	inode->i_mtime.tv_nsec  = attr->mtimensec;
+	/* mtime from server may be stale due to local buffered write */
+	if (!fc->writeback_cache || !S_ISREG(inode->i_mode)) {
+		inode->i_mtime.tv_sec   = attr->mtime;
+		inode->i_mtime.tv_nsec  = attr->mtimensec;
+	}
 	inode->i_ctime.tv_sec   = attr->ctime;
 	inode->i_ctime.tv_nsec  = attr->ctimensec;
 
@@ -250,6 +253,8 @@ static void fuse_init_inode(struct inode *inode, struct fuse_attr *attr)
 {
 	inode->i_mode = attr->mode & S_IFMT;
 	inode->i_size = attr->size;
+	inode->i_mtime.tv_sec  = attr->mtime;
+	inode->i_mtime.tv_nsec = attr->mtimensec;
 	if (S_ISREG(inode->i_mode)) {
 		fuse_init_common(inode);
 		fuse_init_file_inode(inode);
@@ -296,7 +301,9 @@ struct inode *fuse_iget(struct super_block *sb, u64 nodeid,
 		return NULL;
 
 	if ((inode->i_state & I_NEW)) {
-		inode->i_flags |= S_NOATIME|S_NOCMTIME;
+		inode->i_flags |= S_NOATIME;
+		if (!fc->writeback_cache)
+			inode->i_flags |= S_NOCMTIME;
 		inode->i_generation = generation;
 		inode->i_data.backing_dev_info = &fc->bdi;
 		fuse_init_inode(inode, attr);

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