cifs: Support fscache indexing rewrite

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

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 cifs, I've made it render the volume name string as:

	"cifs,<ipaddress>,<sharename>"

     where the sharename has '/' characters replaced with ';'.

     This probably needs rethinking a bit as the total name could exceed
     the maximum filename component length.

     Further, the coherency data is currently just set to 0.  It needs
     something else doing with it - I wonder if it would suffice simply to
     sum the resource_id, vol_create_time and vol_serial_number or maybe
     hash them.

 (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 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) cifs_setattr_*() are made to call fscache_resize() to change the size
     of the cache object.

 (6) The functions to read and write data are stubbed out pending a
     conversion to use netfslib.

Changes
=======
ver #8:
 - Abstract cache invalidation into a helper function.
 - Fix some checkpatch warnings[3].

ver #7:
 - Removed the accidentally added-back call to get the super cookie in
   cifs_root_iget().
 - Fixed the right call to cifs_fscache_get_super_cookie() to take account
   of the "-o fsc" mount flag.

ver #6:
 - Moved the change of gfpflags_allow_blocking() to current_is_kswapd() for
   cifs here.
 - Fixed one of the error paths in cifs_atomic_open() to jump around the
   call to use the cookie.
 - Fixed an additional successful return in the middle of cifs_open() to
   use the cookie on the way out.
 - Only get a volume cookie (and thus inode cookies) when "-o fsc" is
   supplied to mount.

ver #5:
 - Fixed a couple of bits of cookie handling[2]:
   - The cookie should be released in cifs_evict_inode(), not
     cifsFileInfo_put_final().  The cookie needs to persist beyond file
     closure so that writepages will be able to write to it.
   - fscache_use_cookie() needs to be called in cifs_atomic_open() as it is
     for cifs_open().

ver #4:
 - Fixed the use of sizeof with memset.
 - tcon->vol_create_time is __le64 so doesn't need cpu_to_le64().

ver #3:
 - Canonicalise the cifs coherency data to make the cache portable.
 - Set volume coherency data.

ver #2:
 - Use gfpflags_allow_blocking() rather than using flag directly.
 - Upgraded to -rc4 to allow for upstream changes[1].
 - fscache_acquire_volume() now returns errors.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Jeff Layton <jlayton@kernel.org>
cc: Steve French <smfrench@gmail.com>
cc: Shyam Prasad N <nspmangalore@gmail.com>
cc: linux-cifs@vger.kernel.org
cc: linux-cachefs@redhat.com
Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=23b55d673d7527b093cd97b7c217c82e70cd1af0 [1]
Link: https://lore.kernel.org/r/3419813.1641592362@warthog.procyon.org.uk/ [2]
Link: https://lore.kernel.org/r/CAH2r5muTanw9pJqzAHd01d9A8keeChkzGsCEH6=0rHutVLAF-A@mail.gmail.com/ [3]
Link: https://lore.kernel.org/r/163819671009.215744.11230627184193298714.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906982979.143852.10672081929614953210.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967187187.1823006.247415138444991444.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021579335.640689.2681324337038770579.stgit@warthog.procyon.org.uk/ # v4
Link: https://lore.kernel.org/r/3462849.1641593783@warthog.procyon.org.uk/ # v5
Link: https://lore.kernel.org/r/1318953.1642024578@warthog.procyon.org.uk/ # v6
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: dhowells

fs/cifs/Kconfig

@@ -188,7 +188,7 @@ config CIFS_SMB_DIRECT
 
 config CIFS_FSCACHE
 	bool "Provide CIFS client caching support"
-	depends on CIFS=m && FSCACHE_OLD_API || CIFS=y && FSCACHE_OLD_API=y
+	depends on CIFS=m && FSCACHE || CIFS=y && FSCACHE=y
 	help
 	  Makes CIFS FS-Cache capable. Say Y here if you want your CIFS data
 	  to be cached locally on disk through the general filesystem cache

fs/cifs/Makefile

@@ -25,7 +25,7 @@ cifs-$(CONFIG_CIFS_DFS_UPCALL) += cifs_dfs_ref.o dfs_cache.o
 
 cifs-$(CONFIG_CIFS_SWN_UPCALL) += netlink.o cifs_swn.o
 
-cifs-$(CONFIG_CIFS_FSCACHE) += fscache.o cache.o
+cifs-$(CONFIG_CIFS_FSCACHE) += fscache.o
 
 cifs-$(CONFIG_CIFS_SMB_DIRECT) += smbdirect.o
 

fs/cifs/cache.c

@@ -397,6 +397,9 @@ static void
 cifs_evict_inode(struct inode *inode)
 {
 	truncate_inode_pages_final(&inode->i_data);
+	if (inode->i_state & I_PINNING_FSCACHE_WB)
+		cifs_fscache_unuse_inode_cookie(inode, true);
+	cifs_fscache_release_inode_cookie(inode);
 	clear_inode(inode);
 }
 
@@ -721,6 +724,12 @@ static int cifs_show_stats(struct seq_file *s, struct dentry *root)
 }
 #endif
 
+static int cifs_write_inode(struct inode *inode, struct writeback_control *wbc)
+{
+	fscache_unpin_writeback(wbc, cifs_inode_cookie(inode));
+	return 0;
+}
+
 static int cifs_drop_inode(struct inode *inode)
 {
 	struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
@@ -733,6 +742,7 @@ static int cifs_drop_inode(struct inode *inode)
 static const struct super_operations cifs_super_ops = {
 	.statfs = cifs_statfs,
 	.alloc_inode = cifs_alloc_inode,
+	.write_inode	= cifs_write_inode,
 	.free_inode = cifs_free_inode,
 	.drop_inode	= cifs_drop_inode,
 	.evict_inode	= cifs_evict_inode,
@@ -1625,13 +1635,9 @@ init_cifs(void)
 		goto out_destroy_cifsoplockd_wq;
 	}
 
-	rc = cifs_fscache_register();
-	if (rc)
-		goto out_destroy_deferredclose_wq;
-
 	rc = cifs_init_inodecache();
 	if (rc)
-		goto out_unreg_fscache;
+		goto out_destroy_deferredclose_wq;
 
 	rc = cifs_init_mids();
 	if (rc)
@@ -1693,8 +1699,6 @@ init_cifs(void)
 	cifs_destroy_mids();
 out_destroy_inodecache:
 	cifs_destroy_inodecache();
-out_unreg_fscache:
-	cifs_fscache_unregister();
 out_destroy_deferredclose_wq:
 	destroy_workqueue(deferredclose_wq);
 out_destroy_cifsoplockd_wq:
@@ -1730,7 +1734,6 @@ exit_cifs(void)
 	cifs_destroy_request_bufs();
 	cifs_destroy_mids();
 	cifs_destroy_inodecache();
-	cifs_fscache_unregister();
 	destroy_workqueue(deferredclose_wq);
 	destroy_workqueue(cifsoplockd_wq);
 	destroy_workqueue(decrypt_wq);

fs/cifs/cifsfs.c

@@ -668,9 +668,6 @@ struct TCP_Server_Info {
 	unsigned int total_read; /* total amount of data read in this pass */
 	atomic_t in_send; /* requests trying to send */
 	atomic_t num_waiters;   /* blocked waiting to get in sendrecv */
-#ifdef CONFIG_CIFS_FSCACHE
-	struct fscache_cookie   *fscache; /* client index cache cookie */
-#endif
 #ifdef CONFIG_CIFS_STATS2
 	atomic_t num_cmds[NUMBER_OF_SMB2_COMMANDS]; /* total requests by cmd */
 	atomic_t smb2slowcmd[NUMBER_OF_SMB2_COMMANDS]; /* count resps > 1 sec */
@@ -1112,7 +1109,7 @@ struct cifs_tcon {
 	__u32 max_bytes_copy;
 #ifdef CONFIG_CIFS_FSCACHE
 	u64 resource_id;		/* server resource id */
-	struct fscache_cookie *fscache;	/* cookie for share */
+	struct fscache_volume *fscache;	/* cookie for share */
 #endif
 	struct list_head pending_opens;	/* list of incomplete opens */
 	struct cached_fid crfid; /* Cached root fid */

fs/cifs/cifsglob.h

@@ -1444,10 +1444,6 @@ cifs_put_tcp_session(struct TCP_Server_Info *server, int from_reconnect)
 
 	cifs_crypto_secmech_release(server);
 
-	/* fscache server cookies are based on primary channel only */
-	if (!CIFS_SERVER_IS_CHAN(server))
-		cifs_fscache_release_client_cookie(server);
-
 	kfree(server->session_key.response);
 	server->session_key.response = NULL;
 	server->session_key.len = 0;
@@ -1609,14 +1605,6 @@ cifs_get_tcp_session(struct smb3_fs_context *ctx,
 	list_add(&tcp_ses->tcp_ses_list, &cifs_tcp_ses_list);
 	spin_unlock(&cifs_tcp_ses_lock);
 
-	/* fscache server cookies are based on primary channel only */
-	if (!CIFS_SERVER_IS_CHAN(tcp_ses))
-		cifs_fscache_get_client_cookie(tcp_ses);
-#ifdef CONFIG_CIFS_FSCACHE
-	else
-		tcp_ses->fscache = tcp_ses->primary_server->fscache;
-#endif /* CONFIG_CIFS_FSCACHE */
-
 	/* queue echo request delayed work */
 	queue_delayed_work(cifsiod_wq, &tcp_ses->echo, tcp_ses->echo_interval);
 
@@ -3128,7 +3116,8 @@ static int mount_get_conns(struct mount_ctx *mnt_ctx)
 	 * Inside cifs_fscache_get_super_cookie it checks
 	 * that we do not get super cookie twice.
 	 */
-	cifs_fscache_get_super_cookie(tcon);
+	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_FSCACHE)
+		cifs_fscache_get_super_cookie(tcon);
 
 out:
 	mnt_ctx->server = server;

fs/cifs/connect.c

@@ -22,6 +22,7 @@
 #include "cifs_unicode.h"
 #include "fs_context.h"
 #include "cifs_ioctl.h"
+#include "fscache.h"
 
 static void
 renew_parental_timestamps(struct dentry *direntry)
@@ -507,8 +508,12 @@ cifs_atomic_open(struct inode *inode, struct dentry *direntry,
 			server->ops->close(xid, tcon, &fid);
 		cifs_del_pending_open(&open);
 		rc = -ENOMEM;
+		goto out;
 	}
 
+	fscache_use_cookie(cifs_inode_cookie(file_inode(file)),
+			   file->f_mode & FMODE_WRITE);
+
 out:
 	cifs_put_tlink(tlink);
 out_free_xid: