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Subject[RFC PATCH -V1 7/7] fs/9p: Add buffered write support for v9fs. We can now support writeable mmaps.
Date
Based on the original patch from Badari Pulavarty <pbadari@us.ibm.com>

TODO: O_DIRECT
synfc
fsync

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
fs/9p/vfs_addr.c | 182 +++++++++++++++++++++++++++++++++++++++++++++++++-----
fs/9p/vfs_file.c | 54 +++++++++++++++-
2 files changed, 217 insertions(+), 19 deletions(-)

diff --git a/fs/9p/vfs_addr.c b/fs/9p/vfs_addr.c
index 005024c..792c68a 100644
--- a/fs/9p/vfs_addr.c
+++ b/fs/9p/vfs_addr.c
@@ -39,16 +39,16 @@
#include "v9fs.h"
#include "v9fs_vfs.h"
#include "cache.h"
+#include "fid.h"

/**
- * v9fs_vfs_readpage - read an entire page in from 9P
+ * v9fs_fid_readpage - read an entire page in from 9P
*
- * @filp: file being read
+ * @fid: fid being read
* @page: structure to page
*
*/
-
-static int v9fs_vfs_readpage(struct file *filp, struct page *page)
+static int v9fs_fid_readpage(struct p9_fid *fid, struct page *page)
{
int retval;
loff_t offset;
@@ -67,7 +67,7 @@ static int v9fs_vfs_readpage(struct file *filp, struct page *page)
buffer = kmap(page);
offset = page_offset(page);

- retval = v9fs_file_readn(filp, buffer, NULL, PAGE_CACHE_SIZE, offset);
+ retval = v9fs_fid_readn(fid, buffer, NULL, PAGE_CACHE_SIZE, offset);
if (retval < 0) {
v9fs_uncache_page(inode, page);
goto done;
@@ -87,6 +87,19 @@ done:
}

/**
+ * v9fs_vfs_readpage - read an entire page in from 9P
+ *
+ * @filp: file being read
+ * @page: structure to page
+ *
+ */
+
+static int v9fs_vfs_readpage(struct file *filp, struct page *page)
+{
+ return v9fs_fid_readpage(filp->private_data, page);
+}
+
+/**
* v9fs_vfs_readpages - read a set of pages from 9P
*
* @filp: file being read
@@ -124,7 +137,6 @@ static int v9fs_release_page(struct page *page, gfp_t gfp)
{
if (PagePrivate(page))
return 0;
-
return v9fs_fscache_release_page(page, gfp);
}

@@ -137,21 +149,86 @@ static int v9fs_release_page(struct page *page, gfp_t gfp)

static void v9fs_invalidate_page(struct page *page, unsigned long offset)
{
+ /*
+ * If called with zero offset, we should release
+ * the private state assocated with the page
+ */
if (offset == 0)
v9fs_fscache_invalidate_page(page);
}

+static int v9fs_vfs_writepage_locked(struct page *page)
+{
+ char *buffer;
+ int retval, len;
+ loff_t offset, size;
+ mm_segment_t old_fs;
+ struct inode *inode = page->mapping->host;
+
+ size = i_size_read(inode);
+ if (page->index == size >> PAGE_CACHE_SHIFT)
+ len = size & ~PAGE_CACHE_MASK;
+ else
+ len = PAGE_CACHE_SIZE;
+
+ set_page_writeback(page);
+
+ buffer = kmap(page);
+ offset = page_offset(page);
+
+ old_fs = get_fs();
+ set_fs(get_ds());
+ /* We should have i_private always set */
+ BUG_ON(!inode->i_private);
+
+ retval = v9fs_file_write_internal(inode,
+ (struct p9_fid *)inode->i_private,
+ buffer, len, &offset, 0);
+ if (retval > 0)
+ retval = 0;
+
+ set_fs(old_fs);
+ kunmap(page);
+ end_page_writeback(page);
+ return retval;
+}
+
+static int v9fs_vfs_writepage(struct page *page, struct writeback_control *wbc)
+{
+ int retval;
+
+ retval = v9fs_vfs_writepage_locked(page);
+ if (retval < 0) {
+ if (retval == -EAGAIN) {
+ redirty_page_for_writepage(wbc, page);
+ retval = 0;
+ } else {
+ SetPageError(page);
+ mapping_set_error(page->mapping, retval);
+ }
+ } else
+ retval = 0;
+
+ unlock_page(page);
+ return retval;
+}
+
/**
* v9fs_launder_page - Writeback a dirty page
- * Since the writes go directly to the server, we simply return a 0
- * here to indicate success.
- *
* Returns 0 on success.
*/

static int v9fs_launder_page(struct page *page)
{
+ int retval;
+ struct inode *inode = page->mapping->host;
+
v9fs_fscache_wait_on_page_write(inode, page);
+ if (clear_page_dirty_for_io(page)) {
+ retval = v9fs_vfs_writepage_locked(page);
+ if (retval)
+ return retval;
+ }
return 0;
}

@@ -177,6 +254,11 @@ static int v9fs_launder_page(struct page *page)
ssize_t v9fs_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
loff_t pos, unsigned long nr_segs)
{
+ /*
+ * FIXME
+ * Now that we do caching with cache mode enabled, We need
+ * to support direct IO
+ */
P9_DPRINTK(P9_DEBUG_VFS, "v9fs_direct_IO: v9fs_direct_IO (%s) "
"off/no(%lld/%lu) EINVAL\n",
iocb->ki_filp->f_path.dentry->d_name.name,
@@ -184,11 +266,81 @@ ssize_t v9fs_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,

return -EINVAL;
}
+
+static int v9fs_write_begin(struct file *filp, struct address_space *mapping,
+ loff_t pos, unsigned len, unsigned flags,
+ struct page **pagep, void **fsdata)
+{
+ int retval = 0;
+ struct page *page;
+ pgoff_t index = pos >> PAGE_CACHE_SHIFT;
+ struct inode *inode = mapping->host;
+
+start:
+ page = grab_cache_page_write_begin(mapping, index, flags);
+ if (!page) {
+ retval = -ENOMEM;
+ goto out;
+ }
+ BUG_ON(!inode->i_private);
+ if (PageUptodate(page))
+ goto out;
+
+ if (len == PAGE_CACHE_SIZE)
+ goto out;
+
+ retval = v9fs_fid_readpage(inode->i_private, page);
+ page_cache_release(page);
+ if (!retval)
+ goto start;
+out:
+ *pagep = page;
+ return retval;
+}
+
+static int v9fs_write_end(struct file *filp, struct address_space *mapping,
+ loff_t pos, unsigned len, unsigned copied,
+ struct page *page, void *fsdata)
+{
+ loff_t last_pos = pos + copied;
+ struct inode *inode = page->mapping->host;
+
+ if (unlikely(copied < len)) {
+ /*
+ * zero out the rest of the area
+ */
+ unsigned from = pos & (PAGE_CACHE_SIZE - 1);
+
+ zero_user(page, from + copied, len - copied);
+ flush_dcache_page(page);
+ }
+
+ if (!PageUptodate(page))
+ SetPageUptodate(page);
+ /*
+ * No need to use i_size_read() here, the i_size
+ * cannot change under us because we hold the i_mutex.
+ */
+ if (last_pos > inode->i_size)
+ i_size_write(inode, last_pos);
+
+ set_page_dirty(page);
+ unlock_page(page);
+ page_cache_release(page);
+
+ return copied;
+}
+
+
const struct address_space_operations v9fs_addr_operations = {
- .readpage = v9fs_vfs_readpage,
- .readpages = v9fs_vfs_readpages,
- .releasepage = v9fs_release_page,
- .invalidatepage = v9fs_invalidate_page,
- .launder_page = v9fs_launder_page,
- .direct_IO = v9fs_direct_IO,
+ .readpage = v9fs_vfs_readpage,
+ .readpages = v9fs_vfs_readpages,
+ .set_page_dirty = __set_page_dirty_nobuffers,
+ .writepage = v9fs_vfs_writepage,
+ .write_begin = v9fs_write_begin,
+ .write_end = v9fs_write_end,
+ .releasepage = v9fs_release_page,
+ .invalidatepage = v9fs_invalidate_page,
+ .launder_page = v9fs_launder_page,
+ .direct_IO = v9fs_direct_IO,
};
diff --git a/fs/9p/vfs_file.c b/fs/9p/vfs_file.c
index 0f62b26..6e38947 100644
--- a/fs/9p/vfs_file.c
+++ b/fs/9p/vfs_file.c
@@ -44,6 +44,8 @@
#include "fid.h"
#include "cache.h"

+static const struct vm_operations_struct v9fs_file_vm_ops;
+
/**
* v9fs_file_open - open a file (or directory)
* @inode: inode to be opened
@@ -515,6 +517,7 @@ out:
return retval;
}

+
static int v9fs_file_fsync(struct file *filp, int datasync)
{
struct p9_fid *fid;
@@ -544,28 +547,71 @@ int v9fs_file_fsync_dotl(struct file *filp, int datasync)
return retval;
}

+static int
+v9fs_file_mmap(struct file *file, struct vm_area_struct *vma)
+{
+ int retval;
+
+ retval = generic_file_mmap(file, vma);
+ if (!retval)
+ vma->vm_ops = &v9fs_file_vm_ops;
+
+ return retval;
+}
+
+static int
+v9fs_vm_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
+{
+ struct page *page = vmf->page;
+ struct file *filp = vma->vm_file;
+ struct inode *inode = filp->f_path.dentry->d_inode;
+
+
+ P9_DPRINTK(P9_DEBUG_VFS, "page %p fid %lx\n",
+ page, (unsigned long)filp->private_data);
+
+ /* make sure the cache has finished storing the page */
+ v9fs_fscache_wait_on_page_write(inode, page);
+ BUG_ON(!inode->i_private);
+ lock_page(page);
+ if (page->mapping != inode->i_mapping)
+ goto out_unlock;
+
+ return VM_FAULT_LOCKED;
+out_unlock:
+ unlock_page(page);
+ return VM_FAULT_NOPAGE;
+}
+
+static const struct vm_operations_struct v9fs_file_vm_ops = {
+ .fault = filemap_fault,
+ .page_mkwrite = v9fs_vm_page_mkwrite,
+};
+
const struct file_operations v9fs_cached_file_operations = {
.llseek = generic_file_llseek,
.read = do_sync_read,
+ .write = do_sync_write,
.aio_read = generic_file_aio_read,
- .write = v9fs_file_write,
+ .aio_write = generic_file_aio_write,
.open = v9fs_file_open,
.release = v9fs_dir_release,
.lock = v9fs_file_lock,
- .mmap = generic_file_readonly_mmap,
+ .mmap = v9fs_file_mmap,
.fsync = v9fs_file_fsync,
};

const struct file_operations v9fs_cached_file_operations_dotl = {
.llseek = generic_file_llseek,
.read = do_sync_read,
+ .write = do_sync_write,
.aio_read = generic_file_aio_read,
- .write = v9fs_file_write,
+ .aio_write = generic_file_aio_write,
.open = v9fs_file_open,
.release = v9fs_dir_release,
.lock = v9fs_file_lock_dotl,
.flock = v9fs_file_flock_dotl,
- .mmap = generic_file_readonly_mmap,
+ .mmap = v9fs_file_mmap,
.fsync = v9fs_file_fsync_dotl,
};

--
1.7.1


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