9p: Use fscache indexing rewrite and reenable caching

Change the 9p filesystem to take account of the changes to fscache's
indexing rewrite and reenable caching in 9p.

The following changes have been made:

 (1) The fscache_netfs struct is no more, and there's no need to register
     the filesystem as a whole.

 (2) The session cookie is now an fscache_volume cookie, allocated with
     fscache_acquire_volume().  That takes three parameters: a string
     representing the "volume" in the index, a string naming the cache to
     use (or NULL) and a u64 that conveys coherency metadata for the
     volume.

     For 9p, I've made it render the volume name string as:

	"9p,<devname>,<cachetag>"

     where the cachetag is replaced by the aname if it wasn't supplied.

     This probably needs rethinking a bit as the aname can have slashes in
     it.  It might be better to hash the cachetag and use the hash or I
     could substitute commas for the slashes or something.

 (3) The fscache_cookie_def is no more and needed information is passed
     directly to fscache_acquire_cookie().  The cache no longer calls back
     into the filesystem, but rather metadata changes are indicated at
     other times.

     fscache_acquire_cookie() is passed the same keying and coherency
     information as before.

 (4) The functions to set/reset/flush cookies are removed and
     fscache_use_cookie() and fscache_unuse_cookie() are used instead.

     fscache_use_cookie() is passed a flag to indicate if the cookie is
     opened for writing.  fscache_unuse_cookie() is passed updates for the
     metadata if we changed it (ie. if the file was opened for writing).

     These are called when the file is opened or closed.

 (5) wait_on_page_bit[_killable]() is replaced with the specific wait
     functions for the bits waited upon.

 (6) I've got rid of some of the 9p-specific cache helper functions and
     called things like fscache_relinquish_cookie() directly as they'll
     optimise away if v9fs_inode_cookie() returns an unconditional NULL
     (which will be the case if CONFIG_9P_FSCACHE=n).

 (7) v9fs_vfs_setattr() is made to call fscache_resize() to change the size
     of the cache object.

Notes:

 (A) We should call fscache_invalidate() if we detect that the server's
     copy of a file got changed by a third party, but I don't know where to
     do that.  We don't need to do that when allocating the cookie as we
     get a check-and-invalidate when we initially bind to the cache object.

 (B) The copy-to-cache-on-writeback side of things will be handled in
     separate patch.

Changes
=======
ver #3:
 - Canonicalise the cookie key and coherency data to make them
   endianness-independent.

ver #2:
 - Use gfpflags_allow_blocking() rather than using flag directly.
 - fscache_acquire_volume() now returns errors.

Signed-off-by: David Howells <[email protected]>
Acked-by: Jeff Layton <[email protected]>
Tested-by: Dominique Martinet <[email protected]>
cc: Eric Van Hensbergen <[email protected]>
cc: Latchesar Ionkov <[email protected]>
cc: [email protected]
cc: [email protected]
Link: https://lore.kernel.org/r/163819664645.215744.1555314582005286846.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906975017.143852.3459573173204394039.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967178512.1823006.17377493641569138183.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021573143.640689.3977487095697717967.stgit@warthog.procyon.org.uk/ # v4

fs/9p/Kconfig

@@ -14,7 +14,7 @@ config 9P_FS
 if 9P_FS
 config 9P_FSCACHE
 	bool "Enable 9P client caching support"
-	depends on 9P_FS=m && FSCACHE_OLD_API || 9P_FS=y && FSCACHE_OLD_API=y
+	depends on 9P_FS=m && FSCACHE || 9P_FS=y && FSCACHE=y
 	help
 	  Choose Y here to enable persistent, read-only local
 	  caching support for 9p clients using FS-Cache

fs/9p/cache.c

@@ -16,186 +16,61 @@
 #include "v9fs.h"
 #include "cache.h"
 
-#define CACHETAG_LEN  11
-
-struct fscache_netfs v9fs_cache_netfs = {
-	.name		= "9p",
-	.version	= 0,
-};
-
-/*
- * v9fs_random_cachetag - Generate a random tag to be associated
- *			  with a new cache session.
- *
- * The value of jiffies is used for a fairly randomly cache tag.
- */
-
-static
-int v9fs_random_cachetag(struct v9fs_session_info *v9ses)
+int v9fs_cache_session_get_cookie(struct v9fs_session_info *v9ses,
+				  const char *dev_name)
 {
-	v9ses->cachetag = kmalloc(CACHETAG_LEN, GFP_KERNEL);
-	if (!v9ses->cachetag)
-		return -ENOMEM;
+	struct fscache_volume *vcookie;
+	char *name, *p;
 
-	return scnprintf(v9ses->cachetag, CACHETAG_LEN, "%lu", jiffies);
-}
-
-const struct fscache_cookie_def v9fs_cache_session_index_def = {
-	.name		= "9P.session",
-	.type		= FSCACHE_COOKIE_TYPE_INDEX,
-};
+	name = kasprintf(GFP_KERNEL, "9p,%s,%s",
+			 dev_name, v9ses->cachetag ?: v9ses->aname);
+	if (!name)
+		return -ENOMEM;
 
-void v9fs_cache_session_get_cookie(struct v9fs_session_info *v9ses)
-{
-	/* If no cache session tag was specified, we generate a random one. */
-	if (!v9ses->cachetag) {
-		if (v9fs_random_cachetag(v9ses) < 0) {
-			v9ses->fscache = NULL;
-			kfree(v9ses->cachetag);
-			v9ses->cachetag = NULL;
-			return;
+	for (p = name; *p; p++)
+		if (*p == '/')
+			*p = ';';
+
+	vcookie = fscache_acquire_volume(name, NULL, NULL, 0);
+	p9_debug(P9_DEBUG_FSC, "session %p get volume %p (%s)\n",
+		 v9ses, vcookie, name);
+	if (IS_ERR(vcookie)) {
+		if (vcookie != ERR_PTR(-EBUSY)) {
+			kfree(name);
+			return PTR_ERR(vcookie);
 		}
+		pr_err("Cache volume key already in use (%s)\n", name);
+		vcookie = NULL;
 	}
-
-	v9ses->fscache = fscache_acquire_cookie(v9fs_cache_netfs.primary_index,
-						&v9fs_cache_session_index_def,
-						v9ses->cachetag,
-						strlen(v9ses->cachetag),
-						NULL, 0,
-						v9ses, 0, true);
-	p9_debug(P9_DEBUG_FSC, "session %p get cookie %p\n",
-		 v9ses, v9ses->fscache);
-}
-
-void v9fs_cache_session_put_cookie(struct v9fs_session_info *v9ses)
-{
-	p9_debug(P9_DEBUG_FSC, "session %p put cookie %p\n",
-		 v9ses, v9ses->fscache);
-	fscache_relinquish_cookie(v9ses->fscache, NULL, false);
-	v9ses->fscache = NULL;
-}
-
-static enum
-fscache_checkaux v9fs_cache_inode_check_aux(void *cookie_netfs_data,
-					    const void *buffer,
-					    uint16_t buflen,
-					    loff_t object_size)
-{
-	const struct v9fs_inode *v9inode = cookie_netfs_data;
-
-	if (buflen != sizeof(v9inode->qid.version))
-		return FSCACHE_CHECKAUX_OBSOLETE;
-
-	if (memcmp(buffer, &v9inode->qid.version,
-		   sizeof(v9inode->qid.version)))
-		return FSCACHE_CHECKAUX_OBSOLETE;
-
-	return FSCACHE_CHECKAUX_OKAY;
+	v9ses->fscache = vcookie;
+	kfree(name);
+	return 0;
 }
 
-const struct fscache_cookie_def v9fs_cache_inode_index_def = {
-	.name		= "9p.inode",
-	.type		= FSCACHE_COOKIE_TYPE_DATAFILE,
-	.check_aux	= v9fs_cache_inode_check_aux,
-};
-
 void v9fs_cache_inode_get_cookie(struct inode *inode)
 {
 	struct v9fs_inode *v9inode;
 	struct v9fs_session_info *v9ses;
+	__le32 version;
+	__le64 path;
 
 	if (!S_ISREG(inode->i_mode))
 		return;
 
 	v9inode = V9FS_I(inode);
-	if (v9inode->fscache)
+	if (WARN_ON(v9inode->fscache))
 		return;
 
+	version = cpu_to_le32(v9inode->qid.version);
+	path = cpu_to_le64(v9inode->qid.path);
 	v9ses = v9fs_inode2v9ses(inode);
-	v9inode->fscache = fscache_acquire_cookie(v9ses->fscache,
-						  &v9fs_cache_inode_index_def,
-						  &v9inode->qid.path,
-						  sizeof(v9inode->qid.path),
-						  &v9inode->qid.version,
-						  sizeof(v9inode->qid.version),
-						  v9inode,
-						  i_size_read(&v9inode->vfs_inode),
-						  true);
+	v9inode->fscache =
+		fscache_acquire_cookie(v9fs_session_cache(v9ses),
+				       0,
+				       &path, sizeof(path),
+				       &version, sizeof(version),
+				       i_size_read(&v9inode->vfs_inode));
 
 	p9_debug(P9_DEBUG_FSC, "inode %p get cookie %p\n",
 		 inode, v9inode->fscache);
 }
-
-void v9fs_cache_inode_put_cookie(struct inode *inode)
-{
-	struct v9fs_inode *v9inode = V9FS_I(inode);
-
-	if (!v9inode->fscache)
-		return;
-	p9_debug(P9_DEBUG_FSC, "inode %p put cookie %p\n",
-		 inode, v9inode->fscache);
-
-	fscache_relinquish_cookie(v9inode->fscache, &v9inode->qid.version,
-				  false);
-	v9inode->fscache = NULL;
-}
-
-void v9fs_cache_inode_flush_cookie(struct inode *inode)
-{
-	struct v9fs_inode *v9inode = V9FS_I(inode);
-
-	if (!v9inode->fscache)
-		return;
-	p9_debug(P9_DEBUG_FSC, "inode %p flush cookie %p\n",
-		 inode, v9inode->fscache);
-
-	fscache_relinquish_cookie(v9inode->fscache, NULL, true);
-	v9inode->fscache = NULL;
-}
-
-void v9fs_cache_inode_set_cookie(struct inode *inode, struct file *filp)
-{
-	struct v9fs_inode *v9inode = V9FS_I(inode);
-
-	if (!v9inode->fscache)
-		return;
-
-	mutex_lock(&v9inode->fscache_lock);
-
-	if ((filp->f_flags & O_ACCMODE) != O_RDONLY)
-		v9fs_cache_inode_flush_cookie(inode);
-	else
-		v9fs_cache_inode_get_cookie(inode);
-
-	mutex_unlock(&v9inode->fscache_lock);
-}
-
-void v9fs_cache_inode_reset_cookie(struct inode *inode)
-{
-	struct v9fs_inode *v9inode = V9FS_I(inode);
-	struct v9fs_session_info *v9ses;
-	struct fscache_cookie *old;
-
-	if (!v9inode->fscache)
-		return;
-
-	old = v9inode->fscache;
-
-	mutex_lock(&v9inode->fscache_lock);
-	fscache_relinquish_cookie(v9inode->fscache, NULL, true);
-
-	v9ses = v9fs_inode2v9ses(inode);
-	v9inode->fscache = fscache_acquire_cookie(v9ses->fscache,
-						  &v9fs_cache_inode_index_def,
-						  &v9inode->qid.path,
-						  sizeof(v9inode->qid.path),
-						  &v9inode->qid.version,
-						  sizeof(v9inode->qid.version),
-						  v9inode,
-						  i_size_read(&v9inode->vfs_inode),
-						  true);
-	p9_debug(P9_DEBUG_FSC, "inode %p revalidating cookie old %p new %p\n",
-		 inode, old, v9inode->fscache);
-
-	mutex_unlock(&v9inode->fscache_lock);
-}

fs/9p/cache.h

@@ -7,40 +7,21 @@
 
 #ifndef _9P_CACHE_H
 #define _9P_CACHE_H
-#define FSCACHE_USE_NEW_IO_API
+
 #include <linux/fscache.h>
 
 #ifdef CONFIG_9P_FSCACHE
 
-extern struct fscache_netfs v9fs_cache_netfs;
-extern const struct fscache_cookie_def v9fs_cache_session_index_def;
-extern const struct fscache_cookie_def v9fs_cache_inode_index_def;
-
-extern void v9fs_cache_session_get_cookie(struct v9fs_session_info *v9ses);
-extern void v9fs_cache_session_put_cookie(struct v9fs_session_info *v9ses);
+extern int v9fs_cache_session_get_cookie(struct v9fs_session_info *v9ses,
+					  const char *dev_name);
 
 extern void v9fs_cache_inode_get_cookie(struct inode *inode);
-extern void v9fs_cache_inode_put_cookie(struct inode *inode);
-extern void v9fs_cache_inode_flush_cookie(struct inode *inode);
-extern void v9fs_cache_inode_set_cookie(struct inode *inode, struct file *filp);
-extern void v9fs_cache_inode_reset_cookie(struct inode *inode);
-
-extern int __v9fs_cache_register(void);
-extern void __v9fs_cache_unregister(void);
 
 #else /* CONFIG_9P_FSCACHE */
 
 static inline void v9fs_cache_inode_get_cookie(struct inode *inode)
 {
 }
 
-static inline void v9fs_cache_inode_put_cookie(struct inode *inode)
-{
-}
-
-static inline void v9fs_cache_inode_set_cookie(struct inode *inode, struct file *file)
-{
-}
-
 #endif /* CONFIG_9P_FSCACHE */
 #endif /* _9P_CACHE_H */

fs/9p/v9fs.c

@@ -469,7 +469,11 @@ struct p9_fid *v9fs_session_init(struct v9fs_session_info *v9ses,
 
 #ifdef CONFIG_9P_FSCACHE
 	/* register the session for caching */
-	v9fs_cache_session_get_cookie(v9ses);
+	if (v9ses->cache == CACHE_LOOSE || v9ses->cache == CACHE_FSCACHE) {
+		rc = v9fs_cache_session_get_cookie(v9ses, dev_name);
+		if (rc < 0)
+			goto err_clnt;
+	}
 #endif
 	spin_lock(&v9fs_sessionlist_lock);
 	list_add(&v9ses->slist, &v9fs_sessionlist);
@@ -502,8 +506,7 @@ void v9fs_session_close(struct v9fs_session_info *v9ses)
 	}
 
 #ifdef CONFIG_9P_FSCACHE
-	if (v9ses->fscache)
-		v9fs_cache_session_put_cookie(v9ses);
+	fscache_relinquish_volume(v9fs_session_cache(v9ses), NULL, false);
 	kfree(v9ses->cachetag);
 #endif
 	kfree(v9ses->uname);
@@ -665,20 +668,12 @@ static int v9fs_cache_register(void)
 	ret = v9fs_init_inode_cache();
 	if (ret < 0)
 		return ret;
-#ifdef CONFIG_9P_FSCACHE
-	ret = fscache_register_netfs(&v9fs_cache_netfs);
-	if (ret < 0)
-		v9fs_destroy_inode_cache();
-#endif
 	return ret;
 }
 
 static void v9fs_cache_unregister(void)
 {
 	v9fs_destroy_inode_cache();
-#ifdef CONFIG_9P_FSCACHE
-	fscache_unregister_netfs(&v9fs_cache_netfs);
-#endif
 }
 
 /**

fs/9p/v9fs.h

@@ -89,7 +89,7 @@ struct v9fs_session_info {
 	unsigned int cache;
 #ifdef CONFIG_9P_FSCACHE
 	char *cachetag;
-	struct fscache_cookie *fscache;
+	struct fscache_volume *fscache;
 #endif
 
 	char *uname;		/* user name to mount as */
@@ -109,7 +109,6 @@ struct v9fs_session_info {
 
 struct v9fs_inode {
 #ifdef CONFIG_9P_FSCACHE
-	struct mutex fscache_lock;
 	struct fscache_cookie *fscache;
 #endif
 	struct p9_qid qid;
@@ -133,6 +132,16 @@ static inline struct fscache_cookie *v9fs_inode_cookie(struct v9fs_inode *v9inod
 #endif
 }
 
+static inline struct fscache_volume *v9fs_session_cache(struct v9fs_session_info *v9ses)
+{
+#ifdef CONFIG_9P_FSCACHE
+	return v9ses->fscache;
+#else
+	return NULL;
+#endif
+}
+
+
 extern int v9fs_show_options(struct seq_file *m, struct dentry *root);
 
 struct p9_fid *v9fs_session_init(struct v9fs_session_info *v9ses,

fs/9p/vfs_addr.c

@@ -76,7 +76,9 @@ static void v9fs_req_cleanup(struct address_space *mapping, void *priv)
  */
 static bool v9fs_is_cache_enabled(struct inode *inode)
 {
-	return fscache_cookie_enabled(v9fs_inode_cookie(V9FS_I(inode)));
+	struct fscache_cookie *cookie = v9fs_inode_cookie(V9FS_I(inode));
+
+	return fscache_cookie_enabled(cookie) && cookie->cache_priv;
 }
 
 /**
@@ -88,7 +90,7 @@ static int v9fs_begin_cache_operation(struct netfs_read_request *rreq)
 #ifdef CONFIG_9P_FSCACHE
 	struct fscache_cookie *cookie = v9fs_inode_cookie(V9FS_I(rreq->inode));
 
-	return fscache_begin_read_operation(rreq, cookie);
+	return fscache_begin_read_operation(&rreq->cache_resources, cookie);
 #else
 	return -ENOBUFS;
 #endif
@@ -140,7 +142,7 @@ static int v9fs_release_page(struct page *page, gfp_t gfp)
 		return 0;
 #ifdef CONFIG_9P_FSCACHE
 	if (folio_test_fscache(folio)) {
-		if (!(gfp & __GFP_DIRECT_RECLAIM) || !(gfp & __GFP_FS))
+		if (!gfpflags_allow_blocking(gfp) || !(gfp & __GFP_FS))
 			return 0;
 		folio_wait_fscache(folio);
 	}