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Subject: [PATCH 47/67] cachefiles: Put more information in the xattr attached
 to the cache file
From:   David Howells <dhowells@redhat.com>
To:     linux-cachefs@redhat.com
Cc:     dhowells@redhat.com, Trond Myklebust <trondmy@hammerspace.com>,
        Anna Schumaker <anna.schumaker@netapp.com>,
        Steve French <sfrench@samba.org>,
        Dominique Martinet <asmadeus@codewreck.org>,
        Jeff Layton <jlayton@redhat.com>,
        Matthew Wilcox <willy@infradead.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Omar Sandoval <osandov@osandov.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        linux-afs@lists.infradead.org, linux-nfs@vger.kernel.org,
        linux-cifs@vger.kernel.org, ceph-devel@vger.kernel.org,
        v9fs-developer@lists.sourceforge.net,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Date:   Mon, 18 Oct 2021 16:02:01 +0100
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Put some more information into the xattr attached to a cache file including
the size of the object (i_size may get rounded to a block size for DIO
purposes), the point after which the server has no data and a content
mapping type.

Note that the new cache and the old cache will see each other's cache files
as being incoherent and discard them.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/cachefiles/interface.c |    1 +
 fs/cachefiles/internal.h  |   11 +++++++++++
 fs/cachefiles/xattr.c     |   25 +++++++++++++++++++------
 3 files changed, 31 insertions(+), 6 deletions(-)

diff --git a/fs/cachefiles/interface.c b/fs/cachefiles/interface.c
index f90f6ddd07a5..751b0fec4591 100644
--- a/fs/cachefiles/interface.c
+++ b/fs/cachefiles/interface.c
@@ -420,6 +420,7 @@ static bool cachefiles_invalidate_cookie(struct fscache_cookie *cookie)
 
 	old_file = object->file;
 	object->file = new_file;
+	object->content_info = CACHEFILES_CONTENT_NO_DATA;
 	set_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags);
 	set_bit(FSCACHE_COOKIE_NEEDS_UPDATE, &object->cookie->flags);
 
diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h
index a2d2ed2f19eb..1d3e37bca087 100644
--- a/fs/cachefiles/internal.h
+++ b/fs/cachefiles/internal.h
@@ -31,6 +31,16 @@ extern unsigned cachefiles_debug;
 
 #define cachefiles_gfp (__GFP_RECLAIM | __GFP_NORETRY | __GFP_NOMEMALLOC)
 
+enum cachefiles_content {
+	/* These values are saved on disk */
+	CACHEFILES_CONTENT_NO_DATA	= 0, /* No content stored */
+	CACHEFILES_CONTENT_SINGLE	= 1, /* Content is monolithic, all is present */
+	CACHEFILES_CONTENT_ALL		= 2, /* Content is all present, no map */
+	CACHEFILES_CONTENT_BACKFS_MAP	= 3, /* Content is piecemeal, mapped through backing fs */
+	CACHEFILES_CONTENT_DIRTY	= 4, /* Content is dirty (only seen on disk) */
+	nr__cachefiles_content
+};
+
 /*
  * Cached volume representation.
  */
@@ -59,6 +69,7 @@ struct cachefiles_object {
 	u8				key_hash;	/* Hash of object key */
 	unsigned long			flags;
 #define CACHEFILES_OBJECT_USING_TMPFILE	0		/* Have an unlinked tmpfile */
+	enum cachefiles_content		content_info:8;	/* Info about content presence */
 };
 
 extern struct kmem_cache *cachefiles_object_jar;
diff --git a/fs/cachefiles/xattr.c b/fs/cachefiles/xattr.c
index 50b2a4588946..ba3d050a5174 100644
--- a/fs/cachefiles/xattr.c
+++ b/fs/cachefiles/xattr.c
@@ -18,8 +18,11 @@
 #define CACHEFILES_COOKIE_TYPE_DATA 1
 
 struct cachefiles_xattr {
-	uint8_t				type;
-	uint8_t				data[];
+	__be64	object_size;	/* Actual size of the object */
+	__be64	zero_point;	/* Size after which server has no data not written by us */
+	__u8	type;		/* Type of object */
+	__u8	content;	/* Content presence (enum cachefiles_content) */
+	__u8	data[];		/* netfs coherency data */
 } __packed;
 
 static const char cachefiles_xattr_cache[] =
@@ -46,7 +49,10 @@ int cachefiles_set_object_xattr(struct cachefiles_object *object)
 	if (!buf)
 		return -ENOMEM;
 
-	buf->type = CACHEFILES_COOKIE_TYPE_DATA;
+	buf->object_size	= cpu_to_be64(object->cookie->object_size);
+	buf->zero_point		= 0;
+	buf->type		= CACHEFILES_COOKIE_TYPE_DATA;
+	buf->content		= object->content_info;
 	if (len > 0)
 		memcpy(buf->data, fscache_get_aux(object->cookie), len);
 
@@ -54,7 +60,7 @@ int cachefiles_set_object_xattr(struct cachefiles_object *object)
 			   buf, sizeof(struct cachefiles_xattr) + len, 0);
 	if (ret < 0) {
 		trace_cachefiles_coherency(object, file_inode(file)->i_ino,
-					   0,
+					   buf->content,
 					   cachefiles_coherency_set_fail);
 		if (ret != -ENOMEM)
 			cachefiles_io_error_obj(
@@ -62,7 +68,7 @@ int cachefiles_set_object_xattr(struct cachefiles_object *object)
 				"Failed to set xattr with error %d", ret);
 	} else {
 		trace_cachefiles_coherency(object, file_inode(file)->i_ino,
-					   0,
+					   buf->content,
 					   cachefiles_coherency_set_ok);
 	}
 
@@ -100,12 +106,19 @@ int cachefiles_check_auxdata(struct cachefiles_object *object, struct file *file
 		why = cachefiles_coherency_check_type;
 	} else if (memcmp(buf->data, p, len) != 0) {
 		why = cachefiles_coherency_check_aux;
+	} else if (be64_to_cpu(buf->object_size) != object->cookie->object_size) {
+		why = cachefiles_coherency_check_objsize;
+	} else if (buf->content == CACHEFILES_CONTENT_DIRTY) {
+		// TODO: Begin conflict resolution
+		pr_warn("Dirty object in cache\n");
+		why = cachefiles_coherency_check_dirty;
 	} else {
 		why = cachefiles_coherency_check_ok;
 		ret = 0;
 	}
 
-	trace_cachefiles_coherency(object, file_inode(file)->i_ino, 0, why);
+	trace_cachefiles_coherency(object, file_inode(file)->i_ino,
+				   buf->content, why);
 	kfree(buf);
 	return ret;
 }