[PATCH V2] 9P: introduction of a new cache=mmap model.

From: Dominique Martinet
Date: Fri Jan 10 2014 - 15:01:13 EST

- 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@xxxxxx>
Signed-off-by: Eric Van Hensbergen <ericvh@xxxxxxxxx>
---

Same as previous with the extra 4 lines in Documentation's 9p.txt
(figured we might as well want to add the explicit cache=none option)

Sorry again Eric!

(Which made me notice that the second line of loose = is space-aligned
while fscache is tab-aligned, and there are quite a few others of the
same... How are such trivial style fixes handled, in a separate patch?
Or when, like here, there's something else close being changed?)

Documentation/filesystems/9p.txt | 4 ++
fs/9p/v9fs.c | 9 ++-
fs/9p/v9fs.h | 1 +
fs/9p/v9fs_vfs.h | 2 +
fs/9p/vfs_addr.c | 7 ++
fs/9p/vfs_file.c | 140 +++++++++++++++++++++++++++++++++++++--
fs/9p/vfs_inode.c | 22 ++++--
fs/9p/vfs_inode_dotl.c | 9 +--
fs/9p/vfs_super.c | 8 ++-
9 files changed, 183 insertions(+), 19 deletions(-)

diff --git a/Documentation/filesystems/9p.txt b/Documentation/filesystems/9p.txt
index 2c03214..b30a477 100644
--- a/Documentation/filesystems/9p.txt
+++ b/Documentation/filesystems/9p.txt
@@ -69,10 +69,14 @@ OPTIONS
offering several exported file systems.

cache=mode specifies a caching policy. By default, no caches are used.
+ none = default no cache policy, metadata and data
+ alike are synchronous.
loose = no attempts are made at consistency,
intended for exclusive, read-only mounts
fscache = use FS-Cache for a persistent, read-only
cache backend.
+ mmap = minimal cache that is only used for read-write
+ mmap. Nothing else is cached, like cache=none.

debug=n specifies debug level. The debug level is a bitmask.
0x01 = display verbose error messages
diff --git a/fs/9p/v9fs.c b/fs/9p/v9fs.c
index 08f2e1e..14da825 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 a8e127c..099c771 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 dc95a25..b83ebfb 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 9ff073f..c71e886 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 27782bb..a16b0ff 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 af7d531..bb7991c 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 9801306..59dc8e8 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 2756dcd..0afd038 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);
--
1.8.1.4

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