9P: introduction of a new cache=mmap model.

 - Add cache=mmap option
 - Make mmap read-write while keeping it as synchronous as possible
 - Build writeback fid on mmap creation if it is writable

Signed-off-by: Dominique Martinet <dominique.martinet@cea.fr>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

8 files changed, 179 insertions, 19 deletions

diff --git a/fs/9p/v9fs.c b/fs/9p/v9fs.c
index 08f2e1e9a7e6..14da82564f4e 100644
--- a/fs/9p/v9fs.c
+++ b/fs/9p/v9fs.c
@@ -56,7 +56,7 @@ enum {
         /* Options that take no arguments */
         Opt_nodevmap,
         /* Cache options */
-        Opt_cache_loose, Opt_fscache,
+        Opt_cache_loose, Opt_fscache, Opt_mmap,
         /* Access options */
         Opt_access, Opt_posixacl,
         /* Error token */
@@ -74,6 +74,7 @@ static const match_table_t tokens = {
         {Opt_cache, "cache=%s"},
         {Opt_cache_loose, "loose"},
         {Opt_fscache, "fscache"},
+        {Opt_mmap, "mmap"},
         {Opt_cachetag, "cachetag=%s"},
         {Opt_access, "access=%s"},
         {Opt_posixacl, "posixacl"},
@@ -91,6 +92,9 @@ static int get_cache_mode(char *s)
         } else if (!strcmp(s, "fscache")) {
                 version = CACHE_FSCACHE;
                 p9_debug(P9_DEBUG_9P, "Cache mode: fscache\n");
+        } else if (!strcmp(s, "mmap")) {
+                version = CACHE_MMAP;
+                p9_debug(P9_DEBUG_9P, "Cache mode: mmap\n");
         } else if (!strcmp(s, "none")) {
                 version = CACHE_NONE;
                 p9_debug(P9_DEBUG_9P, "Cache mode: none\n");
@@ -220,6 +224,9 @@ static int v9fs_parse_options(struct v9fs_session_info *v9ses, char *opts)
                 case Opt_fscache:
                         v9ses->cache = CACHE_FSCACHE;
                         break;
+                case Opt_mmap:
+                        v9ses->cache = CACHE_MMAP;
+                        break;
                 case Opt_cachetag:
 #ifdef CONFIG_9P_FSCACHE
                         v9ses->cachetag = match_strdup(&args[0]);
diff --git a/fs/9p/v9fs.h b/fs/9p/v9fs.h
index a8e127c89627..099c7712631c 100644
--- a/fs/9p/v9fs.h
+++ b/fs/9p/v9fs.h
@@ -64,6 +64,7 @@ enum p9_session_flags {
 
 enum p9_cache_modes {
         CACHE_NONE,
+        CACHE_MMAP,
         CACHE_LOOSE,
         CACHE_FSCACHE,
 };
diff --git a/fs/9p/v9fs_vfs.h b/fs/9p/v9fs_vfs.h
index dc95a252523d..b83ebfbf3fdc 100644
--- a/fs/9p/v9fs_vfs.h
+++ b/fs/9p/v9fs_vfs.h
@@ -50,6 +50,8 @@ extern const struct dentry_operations v9fs_dentry_operations;
 extern const struct dentry_operations v9fs_cached_dentry_operations;
 extern const struct file_operations v9fs_cached_file_operations;
 extern const struct file_operations v9fs_cached_file_operations_dotl;
+extern const struct file_operations v9fs_mmap_file_operations;
+extern const struct file_operations v9fs_mmap_file_operations_dotl;
 extern struct kmem_cache *v9fs_inode_cache;
 
 struct inode *v9fs_alloc_inode(struct super_block *sb);
diff --git a/fs/9p/vfs_addr.c b/fs/9p/vfs_addr.c
index 9ff073f4090a..c71e88602ff4 100644
--- a/fs/9p/vfs_addr.c
+++ b/fs/9p/vfs_addr.c
@@ -202,6 +202,8 @@ static int v9fs_vfs_writepage(struct page *page, struct writeback_control *wbc)
 {
         int retval;
 
+        p9_debug(P9_DEBUG_VFS, "page %p\n", page);
+
         retval = v9fs_vfs_writepage_locked(page);
         if (retval < 0) {
                 if (retval == -EAGAIN) {
@@ -282,6 +284,9 @@ static int v9fs_write_begin(struct file *filp, struct address_space *mapping,
         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
         struct inode *inode = mapping->host;
 
+
+        p9_debug(P9_DEBUG_VFS, "filp %p, mapping %p\n", filp, mapping);
+
         v9inode = V9FS_I(inode);
 start:
         page = grab_cache_page_write_begin(mapping, index, flags);
@@ -312,6 +317,8 @@ static int v9fs_write_end(struct file *filp, struct address_space *mapping,
         loff_t last_pos = pos + copied;
         struct inode *inode = page->mapping->host;
 
+        p9_debug(P9_DEBUG_VFS, "filp %p, mapping %p\n", filp, mapping);
+
         if (unlikely(copied < len)) {
                 /*
                  * zero out the rest of the area
diff --git a/fs/9p/vfs_file.c b/fs/9p/vfs_file.c
index 27782bb7f4f9..a16b0ff497ca 100644
--- a/fs/9p/vfs_file.c
+++ b/fs/9p/vfs_file.c
@@ -45,6 +45,7 @@
 #include "cache.h"
 
 static const struct vm_operations_struct v9fs_file_vm_ops;
+static const struct vm_operations_struct v9fs_mmap_file_vm_ops;
 
 /**
  * v9fs_file_open - open a file (or directory)
@@ -87,7 +88,8 @@ int v9fs_file_open(struct inode *inode, struct file *file)
 
         file->private_data = fid;
         mutex_lock(&v9inode->v_mutex);
-        if (v9ses->cache && !v9inode->writeback_fid &&
+        if ((v9ses->cache == CACHE_LOOSE || v9ses->cache == CACHE_FSCACHE) &&
+            !v9inode->writeback_fid &&
             ((file->f_flags & O_ACCMODE) != O_RDONLY)) {
                 /*
                  * clone a fid and add it to writeback_fid
@@ -105,7 +107,7 @@ int v9fs_file_open(struct inode *inode, struct file *file)
                 v9inode->writeback_fid = (void *) fid;
         }
         mutex_unlock(&v9inode->v_mutex);
-        if (v9ses->cache)
+        if (v9ses->cache == CACHE_LOOSE || v9ses->cache == CACHE_FSCACHE)
                 v9fs_cache_inode_set_cookie(inode, file);
         return 0;
 out_error:
@@ -579,11 +581,12 @@ int v9fs_file_fsync_dotl(struct file *filp, loff_t start, loff_t end,
 }
 
 static int
-v9fs_file_mmap(struct file *file, struct vm_area_struct *vma)
+v9fs_file_mmap(struct file *filp, struct vm_area_struct *vma)
 {
         int retval;
 
-        retval = generic_file_mmap(file, vma);
+
+        retval = generic_file_mmap(filp, vma);
         if (!retval)
                 vma->vm_ops = &v9fs_file_vm_ops;
 
@@ -591,6 +594,43 @@ v9fs_file_mmap(struct file *file, struct vm_area_struct *vma)
 }
 
 static int
+v9fs_mmap_file_mmap(struct file *filp, struct vm_area_struct *vma)
+{
+        int retval;
+        struct inode *inode;
+        struct v9fs_inode *v9inode;
+        struct p9_fid *fid;
+
+        inode = file_inode(filp);
+        v9inode = V9FS_I(inode);
+        mutex_lock(&v9inode->v_mutex);
+        if (!v9inode->writeback_fid &&
+            (vma->vm_flags & VM_WRITE)) {
+                /*
+                 * clone a fid and add it to writeback_fid
+                 * we do it during mmap instead of
+                 * page dirty time via write_begin/page_mkwrite
+                 * because we want write after unlink usecase
+                 * to work.
+                 */
+                fid = v9fs_writeback_fid(filp->f_path.dentry);
+                if (IS_ERR(fid)) {
+                        retval = PTR_ERR(fid);
+                        mutex_unlock(&v9inode->v_mutex);
+                        return retval;
+                }
+                v9inode->writeback_fid = (void *) fid;
+        }
+        mutex_unlock(&v9inode->v_mutex);
+
+        retval = generic_file_mmap(filp, vma);
+        if (!retval)
+                vma->vm_ops = &v9fs_mmap_file_vm_ops;
+
+        return retval;
+}
+
+static int
 v9fs_vm_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
 {
         struct v9fs_inode *v9inode;
@@ -658,6 +698,22 @@ v9fs_cached_file_read(struct file *filp, char __user *data, size_t count,
         return do_sync_read(filp, data, count, offset);
 }
 
+/**
+ * v9fs_mmap_file_read - read from a file
+ * @filp: file pointer to read
+ * @udata: user data buffer to read data into
+ * @count: size of buffer
+ * @offset: offset at which to read data
+ *
+ */
+static ssize_t
+v9fs_mmap_file_read(struct file *filp, char __user *data, size_t count,
+                      loff_t *offset)
+{
+        /* TODO: Check if there are dirty pages */
+        return v9fs_file_read(filp, data, count, offset);
+}
+
 static ssize_t
 v9fs_direct_write(struct file *filp, const char __user * data,
                   size_t count, loff_t *offsetp)
@@ -728,12 +784,65 @@ v9fs_cached_file_write(struct file *filp, const char __user * data,
         return do_sync_write(filp, data, count, offset);
 }
 
+
+/**
+ * v9fs_mmap_file_write - write to a file
+ * @filp: file pointer to write
+ * @data: data buffer to write data from
+ * @count: size of buffer
+ * @offset: offset at which to write data
+ *
+ */
+static ssize_t
+v9fs_mmap_file_write(struct file *filp, const char __user *data,
+                       size_t count, loff_t *offset)
+{
+        /*
+         * TODO: invalidate mmaps on filp's inode between
+         * offset and offset+count
+         */
+        return v9fs_file_write(filp, data, count, offset);
+}
+
+static void v9fs_mmap_vm_close(struct vm_area_struct *vma)
+{
+        struct inode *inode;
+
+        struct writeback_control wbc = {
+                .nr_to_write = LONG_MAX,
+                .sync_mode = WB_SYNC_ALL,
+                .range_start = vma->vm_pgoff * PAGE_SIZE,
+                 /* absolute end, byte at end included */
+                .range_end = vma->vm_pgoff * PAGE_SIZE +
+                        (vma->vm_end - vma->vm_start - 1),
+        };
+
+
+        p9_debug(P9_DEBUG_VFS, "9p VMA close, %p, flushing", vma);
+
+        inode = file_inode(vma->vm_file);
+
+        if (!mapping_cap_writeback_dirty(inode->i_mapping))
+                wbc.nr_to_write = 0;
+
+        might_sleep();
+        sync_inode(inode, &wbc);
+}
+
+
 static const struct vm_operations_struct v9fs_file_vm_ops = {
         .fault = filemap_fault,
         .page_mkwrite = v9fs_vm_page_mkwrite,
         .remap_pages = generic_file_remap_pages,
 };
 
+static const struct vm_operations_struct v9fs_mmap_file_vm_ops = {
+        .close = v9fs_mmap_vm_close,
+        .fault = filemap_fault,
+        .page_mkwrite = v9fs_vm_page_mkwrite,
+        .remap_pages = generic_file_remap_pages,
+};
+
 
 const struct file_operations v9fs_cached_file_operations = {
         .llseek = generic_file_llseek,
@@ -784,3 +893,26 @@ const struct file_operations v9fs_file_operations_dotl = {
         .mmap = generic_file_readonly_mmap,
         .fsync = v9fs_file_fsync_dotl,
 };
+
+const struct file_operations v9fs_mmap_file_operations = {
+        .llseek = generic_file_llseek,
+        .read = v9fs_mmap_file_read,
+        .write = v9fs_mmap_file_write,
+        .open = v9fs_file_open,
+        .release = v9fs_dir_release,
+        .lock = v9fs_file_lock,
+        .mmap = v9fs_mmap_file_mmap,
+        .fsync = v9fs_file_fsync,
+};
+
+const struct file_operations v9fs_mmap_file_operations_dotl = {
+        .llseek = generic_file_llseek,
+        .read = v9fs_mmap_file_read,
+        .write = v9fs_mmap_file_write,
+        .open = v9fs_file_open,
+        .release = v9fs_dir_release,
+        .lock = v9fs_file_lock_dotl,
+        .flock = v9fs_file_flock_dotl,
+        .mmap = v9fs_mmap_file_mmap,
+        .fsync = v9fs_file_fsync_dotl,
+};
diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
index af7d531bdecd..bb7991c7e5c7 100644
--- a/fs/9p/vfs_inode.c
+++ b/fs/9p/vfs_inode.c
@@ -299,15 +299,22 @@ int v9fs_init_inode(struct v9fs_session_info *v9ses,
         case S_IFREG:
                 if (v9fs_proto_dotl(v9ses)) {
                         inode->i_op = &v9fs_file_inode_operations_dotl;
-                        if (v9ses->cache)
+                        if (v9ses->cache == CACHE_LOOSE ||
+                            v9ses->cache == CACHE_FSCACHE)
                                 inode->i_fop =
                                         &v9fs_cached_file_operations_dotl;
+                        else if (v9ses->cache == CACHE_MMAP)
+                                inode->i_fop = &v9fs_mmap_file_operations_dotl;
                         else
                                 inode->i_fop = &v9fs_file_operations_dotl;
                 } else {
                         inode->i_op = &v9fs_file_inode_operations;
-                        if (v9ses->cache)
-                                inode->i_fop = &v9fs_cached_file_operations;
+                        if (v9ses->cache == CACHE_LOOSE ||
+                            v9ses->cache == CACHE_FSCACHE)
+                                inode->i_fop =
+                                        &v9fs_cached_file_operations;
+                        else if (v9ses->cache == CACHE_MMAP)
+                                inode->i_fop = &v9fs_mmap_file_operations;
                         else
                                 inode->i_fop = &v9fs_file_operations;
                 }
@@ -810,7 +817,7 @@ struct dentry *v9fs_vfs_lookup(struct inode *dir, struct dentry *dentry,
          * unlink. For cached mode create calls request for new
          * inode. But with cache disabled, lookup should do this.
          */
-        if (v9ses->cache)
+        if (v9ses->cache == CACHE_LOOSE || v9ses->cache == CACHE_FSCACHE)
                 inode = v9fs_get_inode_from_fid(v9ses, fid, dir->i_sb);
         else
                 inode = v9fs_get_new_inode_from_fid(v9ses, fid, dir->i_sb);
@@ -876,7 +883,8 @@ v9fs_vfs_atomic_open(struct inode *dir, struct dentry *dentry,
         v9fs_invalidate_inode_attr(dir);
         v9inode = V9FS_I(dentry->d_inode);
         mutex_lock(&v9inode->v_mutex);
-        if (v9ses->cache && !v9inode->writeback_fid &&
+        if ((v9ses->cache == CACHE_LOOSE || v9ses->cache == CACHE_FSCACHE) &&
+            !v9inode->writeback_fid &&
             ((flags & O_ACCMODE) != O_RDONLY)) {
                 /*
                  * clone a fid and add it to writeback_fid
@@ -899,7 +907,7 @@ v9fs_vfs_atomic_open(struct inode *dir, struct dentry *dentry,
                 goto error;
 
         file->private_data = fid;
-        if (v9ses->cache)
+        if (v9ses->cache == CACHE_LOOSE || v9ses->cache == CACHE_FSCACHE)
                 v9fs_cache_inode_set_cookie(dentry->d_inode, file);
 
         *opened |= FILE_CREATED;
@@ -1477,7 +1485,7 @@ int v9fs_refresh_inode(struct p9_fid *fid, struct inode *inode)
          */
         i_size = inode->i_size;
         v9fs_stat2inode(st, inode, inode->i_sb);
-        if (v9ses->cache)
+        if (v9ses->cache == CACHE_LOOSE || v9ses->cache == CACHE_FSCACHE)
                 inode->i_size = i_size;
         spin_unlock(&inode->i_lock);
 out:
diff --git a/fs/9p/vfs_inode_dotl.c b/fs/9p/vfs_inode_dotl.c
index 98013068f35b..59dc8e87647f 100644
--- a/fs/9p/vfs_inode_dotl.c
+++ b/fs/9p/vfs_inode_dotl.c
@@ -330,7 +330,8 @@ v9fs_vfs_atomic_open_dotl(struct inode *dir, struct dentry *dentry,
 
         v9inode = V9FS_I(inode);
         mutex_lock(&v9inode->v_mutex);
-        if (v9ses->cache && !v9inode->writeback_fid &&
+        if ((v9ses->cache == CACHE_LOOSE || v9ses->cache == CACHE_FSCACHE) &&
+            !v9inode->writeback_fid &&
             ((flags & O_ACCMODE) != O_RDONLY)) {
                 /*
                  * clone a fid and add it to writeback_fid
@@ -353,7 +354,7 @@ v9fs_vfs_atomic_open_dotl(struct inode *dir, struct dentry *dentry,
         if (err)
                 goto err_clunk_old_fid;
         file->private_data = ofid;
-        if (v9ses->cache)
+        if (v9ses->cache == CACHE_LOOSE || v9ses->cache == CACHE_FSCACHE)
                 v9fs_cache_inode_set_cookie(inode, file);
         *opened |= FILE_CREATED;
 out:
@@ -710,7 +711,7 @@ v9fs_vfs_symlink_dotl(struct inode *dir, struct dentry *dentry,
         }
 
         v9fs_invalidate_inode_attr(dir);
-        if (v9ses->cache) {
+        if (v9ses->cache == CACHE_LOOSE || v9ses->cache == CACHE_FSCACHE) {
                 /* Now walk from the parent so we can get an unopened fid. */
                 fid = p9_client_walk(dfid, 1, &name, 1);
                 if (IS_ERR(fid)) {
@@ -965,7 +966,7 @@ int v9fs_refresh_inode_dotl(struct p9_fid *fid, struct inode *inode)
          */
         i_size = inode->i_size;
         v9fs_stat2inode_dotl(st, inode);
-        if (v9ses->cache)
+        if (v9ses->cache == CACHE_LOOSE || v9ses->cache == CACHE_FSCACHE)
                 inode->i_size = i_size;
         spin_unlock(&inode->i_lock);
 out:
diff --git a/fs/9p/vfs_super.c b/fs/9p/vfs_super.c
index 2756dcd5de6e..0afd0382822b 100644
--- a/fs/9p/vfs_super.c
+++ b/fs/9p/vfs_super.c
@@ -144,7 +144,7 @@ static struct dentry *v9fs_mount(struct file_system_type *fs_type, int flags,
         }
         v9fs_fill_super(sb, v9ses, flags, data);
 
-        if (v9ses->cache)
+        if (v9ses->cache == CACHE_LOOSE || v9ses->cache == CACHE_FSCACHE)
                 sb->s_d_op = &v9fs_cached_dentry_operations;
         else
                 sb->s_d_op = &v9fs_dentry_operations;
@@ -282,7 +282,7 @@ static int v9fs_drop_inode(struct inode *inode)
 {
         struct v9fs_session_info *v9ses;
         v9ses = v9fs_inode2v9ses(inode);
-        if (v9ses->cache)
+        if (v9ses->cache == CACHE_LOOSE || v9ses->cache == CACHE_FSCACHE)
                 return generic_drop_inode(inode);
         /*
          * in case of non cached mode always drop the
@@ -325,10 +325,12 @@ static int v9fs_write_inode_dotl(struct inode *inode,
          * send an fsync request to server irrespective of
          * wbc->sync_mode.
          */
-        p9_debug(P9_DEBUG_VFS, "%s: inode %p\n", __func__, inode);
         v9inode = V9FS_I(inode);
+        p9_debug(P9_DEBUG_VFS, "%s: inode %p, writeback_fid %p\n",
+                 __func__, inode, v9inode->writeback_fid);
         if (!v9inode->writeback_fid)
                 return 0;
+
         ret = p9_client_fsync(v9inode->writeback_fid, 0);
         if (ret < 0) {
                 __mark_inode_dirty(inode, I_DIRTY_DATASYNC);