9p: implement optional loose read cache

While cacheing is generally frowned upon in the 9p world, it has its
place -- particularly in situations where the remote file system is
exclusive and/or read-only.  The vacfs views of venti content addressable
store are a real-world instance of such a situation.  To facilitate higher
performance for these workloads (and eventually use the fscache patches),
we have enabled a "loose" cache mode which does not attempt to maintain
any form of consistency on the page-cache or dcache.  This results in over
two orders of magnitude performance improvement for cacheable block reads
in the Bonnie benchmark.  The more aggressive use of the dcache also seems
to improve metadata operational performance.

Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

diff --git a/Documentation/filesystems/00-INDEX b/Documentation/filesystems/00-INDEX
index 4dc28cc935037c3b9c8f7cdc4dbb26854fbc2ea8..571785887a4f46e2341051388cc51d8dbb5cc8d7 100644 (file)
--- a/Documentation/filesystems/00-INDEX
+++ b/Documentation/filesystems/00-INDEX
@@ -4,6 +4,8 @@ Exporting
        - explanation of how to make filesystems exportable.
 Locking
        - info on locking rules as they pertain to Linux VFS.
+9p.txt
+       - 9p (v9fs) is an implementation of the Plan 9 remote fs protocol.
 adfs.txt
        - info and mount options for the Acorn Advanced Disc Filing System.
 afs.txt
@@ -82,8 +84,6 @@ udf.txt
        - info and mount options for the UDF filesystem.
 ufs.txt
        - info on the ufs filesystem.
-v9fs.txt
-       - v9fs is a Unix implementation of the Plan 9 9p remote fs protocol.
 vfat.txt
        - info on using the VFAT filesystem used in Windows NT and Windows 95
 vfs.txt

diff --git a/Documentation/filesystems/9p.txt b/Documentation/filesystems/9p.txt
index 4d075a4558f9d8ad61799cfcf6028edd497a59b3..bbd8b28c13de917dc3bdc6d04b1bc38e9aea2768 100644 (file)
--- a/Documentation/filesystems/9p.txt
+++ b/Documentation/filesystems/9p.txt
@@ -40,6 +40,10 @@ OPTIONS
   aname=name   aname specifies the file tree to access when the server is
                offering several exported file systems.
 
+  cache=mode   specifies a cacheing policy.  By default, no caches are used.
+                       loose = no attempts are made at consistency,
+                                intended for exclusive, read-only mounts
+
   debug=n      specifies debug level.  The debug level is a bitmask.
                        0x01 = display verbose error messages
                        0x02 = developer debug (DEBUG_CURRENT)

diff --git a/fs/9p/fid.c b/fs/9p/fid.c
index a9b6301a04fcce2d0c5302ecfbb66a0de9cf8770..90419715c7e95cc52187d5b362967b0c1d8e0e4d 100644 (file)
--- a/fs/9p/fid.c
+++ b/fs/9p/fid.c
@@ -136,7 +136,8 @@ struct v9fs_fid *v9fs_fid_lookup(struct dentry *dentry)
 }
 
 /**
- * v9fs_fid_clone - lookup the fid for a dentry, clone a private copy and release it
+ * v9fs_fid_clone - lookup the fid for a dentry, clone a private copy and
+ *                     release it
  * @dentry: dentry to look for fid in
  *
  * find a fid in the dentry and then clone to a new private fid

diff --git a/fs/9p/v9fs.c b/fs/9p/v9fs.c
index d9b561ba5e581cfeda7728e8c072428d40a85433..6ad6f192b6e45db7c66df77a170779512c34c29f 100644 (file)
--- a/fs/9p/v9fs.c
+++ b/fs/9p/v9fs.c
@@ -53,6 +53,8 @@ enum {
        Opt_uname, Opt_remotename,
        /* Options that take no arguments */
        Opt_legacy, Opt_nodevmap, Opt_unix, Opt_tcp, Opt_fd,
+       /* Cache options */
+       Opt_cache_loose,
        /* Error token */
        Opt_err
 };
@@ -76,6 +78,8 @@ static match_table_t tokens = {
        {Opt_fd, "fd"},
        {Opt_legacy, "noextend"},
        {Opt_nodevmap, "nodevmap"},
+       {Opt_cache_loose, "cache=loose"},
+       {Opt_cache_loose, "loose"},
        {Opt_err, NULL}
 };
 
@@ -106,6 +110,7 @@ static void v9fs_parse_options(char *options, struct v9fs_session_info *v9ses)
        v9ses->debug = 0;
        v9ses->rfdno = ~0;
        v9ses->wfdno = ~0;
+       v9ses->cache = 0;
 
        if (!options)
                return;
@@ -121,7 +126,6 @@ static void v9fs_parse_options(char *options, struct v9fs_session_info *v9ses)
                                        "integer field, but no integer?\n");
                                continue;
                        }
-
                }
                switch (token) {
                case Opt_port:
@@ -169,6 +173,9 @@ static void v9fs_parse_options(char *options, struct v9fs_session_info *v9ses)
                case Opt_nodevmap:
                        v9ses->nodev = 1;
                        break;
+               case Opt_cache_loose:
+                       v9ses->cache = CACHE_LOOSE;
+                       break;
                default:
                        continue;
                }

diff --git a/fs/9p/v9fs.h b/fs/9p/v9fs.h
index c134d104cb28f56b606d51886a7e34f93f02c378..820bf5ca35d88b8dd2c03ac619b88b16d8ac45c2 100644 (file)
--- a/fs/9p/v9fs.h
+++ b/fs/9p/v9fs.h
@@ -47,7 +47,7 @@ struct v9fs_session_info {
        unsigned int afid;      /* authentication fid */
        unsigned int rfdno;     /* read file descriptor number */
        unsigned int wfdno;     /* write file descriptor number */
-
+       unsigned int cache;     /* cache mode */
 
        char *name;             /* user name to mount as */
        char *remotename;       /* name of remote hierarchy being mounted */
@@ -73,6 +73,13 @@ enum {
        PROTO_FD,
 };
 
+/* possible values of ->cache */
+/* eventually support loose, tight, time, session, default always none */
+enum {
+       CACHE_NONE,             /* default */
+       CACHE_LOOSE,            /* no consistency */
+};
+
 extern struct dentry *v9fs_debugfs_root;
 
 int v9fs_session_init(struct v9fs_session_info *, const char *, char *);

diff --git a/fs/9p/v9fs_vfs.h b/fs/9p/v9fs_vfs.h
index 450b0c1b385e62f31db2d74ce6990fd67f8aeedc..8ada4c5c5d70b47abf82297ec8337c9bcb403e98 100644 (file)
--- a/fs/9p/v9fs_vfs.h
+++ b/fs/9p/v9fs_vfs.h
@@ -40,8 +40,10 @@
 extern struct file_system_type v9fs_fs_type;
 extern const struct address_space_operations v9fs_addr_operations;
 extern const struct file_operations v9fs_file_operations;
+extern const struct file_operations v9fs_cached_file_operations;
 extern const struct file_operations v9fs_dir_operations;
 extern struct dentry_operations v9fs_dentry_operations;
+extern struct dentry_operations v9fs_cached_dentry_operations;
 
 struct inode *v9fs_get_inode(struct super_block *sb, int mode);
 ino_t v9fs_qid2ino(struct v9fs_qid *qid);

diff --git a/fs/9p/vfs_addr.c b/fs/9p/vfs_addr.c
index cc24abf232d5818c375836b744759916b88f24ac..bed48fa96521862d6aa26d503df589bbc4993bdd 100644 (file)
--- a/fs/9p/vfs_addr.c
+++ b/fs/9p/vfs_addr.c
@@ -63,6 +63,8 @@ static int v9fs_vfs_readpage(struct file *filp, struct page *page)
        int total = 0;
        int result = 0;
 
+       dprintk(DEBUG_VFS, "\n");
+
        buffer = kmap(page);
        do {
                if (count < rsize)

diff --git a/fs/9p/vfs_dentry.c b/fs/9p/vfs_dentry.c
index 062daa6000ab55a33441b8bcac7aa4375727fe14..ddffd8aa902d65d1c389fc3a86d845ca62238210 100644 (file)
--- a/fs/9p/vfs_dentry.c
+++ b/fs/9p/vfs_dentry.c
@@ -53,9 +53,30 @@
 static int v9fs_dentry_delete(struct dentry *dentry)
 {
        dprintk(DEBUG_VFS, " dentry: %s (%p)\n", dentry->d_iname, dentry);
+
        return 1;
 }
 
+/**
+ * v9fs_cached_dentry_delete - called when dentry refcount equals 0
+ * @dentry:  dentry in question
+ *
+ * Only return 1 if our inode is invalid.  Only non-synthetic files
+ * (ones without mtime == 0) should be calling this function.
+ *
+ */
+
+static int v9fs_cached_dentry_delete(struct dentry *dentry)
+{
+       struct inode *inode = dentry->d_inode;
+       dprintk(DEBUG_VFS, " dentry: %s (%p)\n", dentry->d_iname, dentry);
+
+       if(!inode)
+               return 1;
+
+       return 0;
+}
+
 /**
  * v9fs_dentry_release - called when dentry is going to be freed
  * @dentry:  dentry that is being release
@@ -87,6 +108,11 @@ void v9fs_dentry_release(struct dentry *dentry)
        }
 }
 
+struct dentry_operations v9fs_cached_dentry_operations = {
+       .d_delete = v9fs_cached_dentry_delete,
+       .d_release = v9fs_dentry_release,
+};
+
 struct dentry_operations v9fs_dentry_operations = {
        .d_delete = v9fs_dentry_delete,
        .d_release = v9fs_dentry_release,

diff --git a/fs/9p/vfs_file.c b/fs/9p/vfs_file.c
index 6c78343cf69023e5220c6a50127b33325c0f1c97..653dfa5b253174bcf4712211ece50540beed06e8 100644 (file)
--- a/fs/9p/vfs_file.c
+++ b/fs/9p/vfs_file.c
@@ -79,6 +79,13 @@ int v9fs_file_open(struct inode *inode, struct file *file)
        vfid->filp = file;
        kfree(fcall);
 
+       if((vfid->qid.version) && (v9ses->cache)) {
+               dprintk(DEBUG_VFS, "cached");
+               /* enable cached file options */
+               if(file->f_op == &v9fs_file_operations)
+                       file->f_op = &v9fs_cached_file_operations;
+       }
+
        return 0;
 
 Clunk_Fid:
@@ -238,6 +245,17 @@ v9fs_file_write(struct file *filp, const char __user * data,
        return total;
 }
 
+const struct file_operations v9fs_cached_file_operations = {
+       .llseek = generic_file_llseek,
+       .read = do_sync_read,
+       .aio_read = generic_file_aio_read,
+       .write = v9fs_file_write,
+       .open = v9fs_file_open,
+       .release = v9fs_dir_release,
+       .lock = v9fs_file_lock,
+       .mmap = generic_file_mmap,
+};
+
 const struct file_operations v9fs_file_operations = {
        .llseek = generic_file_llseek,
        .read = v9fs_file_read,

diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
index 5cf22134826bded20a24b57be206f2ff3624f3b4..124a085d1f2e16265da9658cb339bbfb87e15287 100644 (file)
--- a/fs/9p/vfs_inode.c
+++ b/fs/9p/vfs_inode.c
@@ -504,7 +504,10 @@ v9fs_vfs_create(struct inode *dir, struct dentry *dentry, int mode,
                goto error;
        }
 
-       dentry->d_op = &v9fs_dentry_operations;
+       if(v9ses->cache)
+               dentry->d_op = &v9fs_cached_dentry_operations;
+       else
+               dentry->d_op = &v9fs_dentry_operations;
        d_instantiate(dentry, inode);
 
        if (nd && nd->flags & LOOKUP_OPEN) {
@@ -589,7 +592,10 @@ static int v9fs_vfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
                goto error;
        }
 
-       dentry->d_op = &v9fs_dentry_operations;
+       if(v9ses->cache)
+               dentry->d_op = &v9fs_cached_dentry_operations;
+       else
+               dentry->d_op = &v9fs_dentry_operations;
        d_instantiate(dentry, inode);
        return 0;
 
@@ -626,7 +632,6 @@ static struct dentry *v9fs_vfs_lookup(struct inode *dir, struct dentry *dentry,
 
        sb = dir->i_sb;
        v9ses = v9fs_inode2v9ses(dir);
-       dentry->d_op = &v9fs_dentry_operations;
        dirfid = v9fs_fid_lookup(dentry->d_parent);
 
        if(IS_ERR(dirfid))
@@ -697,6 +702,10 @@ static struct dentry *v9fs_vfs_lookup(struct inode *dir, struct dentry *dentry,
 
        fid->qid = fcall->params.rstat.stat.qid;
        v9fs_stat2inode(&fcall->params.rstat.stat, inode, inode->i_sb);
+       if((fid->qid.version)&&(v9ses->cache))
+               dentry->d_op = &v9fs_cached_dentry_operations;
+       else
+               dentry->d_op = &v9fs_dentry_operations;
 
        d_add(dentry, inode);
        kfree(fcall);
@@ -1184,7 +1193,10 @@ static int v9fs_vfs_mkspecial(struct inode *dir, struct dentry *dentry,
                goto free_vfid;
        }
 
-       dentry->d_op = &v9fs_dentry_operations;
+       if(v9ses->cache)
+               dentry->d_op = &v9fs_cached_dentry_operations;
+       else
+               dentry->d_op = &v9fs_dentry_operations;
        d_instantiate(dentry, inode);
        return 0;