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Subject[PATCH 11/13] afs: Copy local writes to the cache when writing to the server
From
Date
When writing to the server from afs_writepage() or afs_writepages(), copy
the data to the cache object too.

Signed-off-by: David Howells <dhowells@redhat.com>
---

fs/afs/write.c | 132 ++++++++++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 128 insertions(+), 4 deletions(-)

diff --git a/fs/afs/write.c b/fs/afs/write.c
index cb27027c06bb..10c60837775e 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -13,6 +13,9 @@
#include <linux/pagevec.h>
#include "internal.h"

+static void afs_write_to_cache(struct afs_vnode *vnode,
+ pgoff_t start, pgoff_t end, loff_t a, loff_t b);
+
/*
* mark a page as having been made dirty and thus needing writeback
*/
@@ -427,6 +430,8 @@ static int afs_write_back_from_locked_page(struct address_space *mapping,
count = 1;
if (test_set_page_writeback(primary_page))
BUG();
+ if (TestSetPageFsCache(primary_page))
+ BUG();

/* Find all consecutive lockable dirty pages that have contiguous
* written regions, stopping when we find a page that is not
@@ -475,7 +480,8 @@ static int afs_write_back_from_locked_page(struct address_space *mapping,
break;
if (!trylock_page(page))
break;
- if (!PageDirty(page) || PageWriteback(page)) {
+ if (!PageDirty(page) || PageWriteback(page) ||
+ PageFsCache(page)) {
unlock_page(page);
break;
}
@@ -497,6 +503,8 @@ static int afs_write_back_from_locked_page(struct address_space *mapping,
BUG();
if (test_set_page_writeback(page))
BUG();
+ if (TestSetPageFsCache(page))
+ BUG();
unlock_page(page);
put_page(page);
}
@@ -534,6 +542,11 @@ static int afs_write_back_from_locked_page(struct address_space *mapping,
end = i_size;

if (pos < i_size) {
+ /* Speculatively write to the cache. We have to fix this up
+ * later if the store fails.
+ */
+ afs_write_to_cache(vnode, first, last, pos, end);
+
iov_iter_mapping(&iter, WRITE, mapping, pos, end - pos);
ret = afs_store_data(vnode, &iter, pos, first, last);
} else {
@@ -592,6 +605,10 @@ int afs_writepage(struct page *page, struct writeback_control *wbc)

_enter("{%lx},", page->index);

+#ifdef CONFIG_AFS_FSCACHE
+ wait_on_page_fscache(page);
+#endif
+
ret = afs_write_back_from_locked_page(page->mapping, wbc, page,
wbc->range_end >> PAGE_SHIFT);
if (ret < 0) {
@@ -619,7 +636,7 @@ static int afs_writepages_region(struct address_space *mapping,

do {
n = find_get_pages_range_tag(mapping, &index, end,
- PAGECACHE_TAG_DIRTY, 1, &page);
+ PAGECACHE_TAG_DIRTY, 1, &page);
if (!n)
break;

@@ -644,10 +661,14 @@ static int afs_writepages_region(struct address_space *mapping,
continue;
}

- if (PageWriteback(page)) {
+ if (PageWriteback(page) || PageFsCache(page)) {
unlock_page(page);
- if (wbc->sync_mode != WB_SYNC_NONE)
+ if (wbc->sync_mode != WB_SYNC_NONE) {
wait_on_page_writeback(page);
+#ifdef CONFIG_AFS_FSCACHE
+ wait_on_page_fscache(page);
+#endif
+ }
put_page(page);
continue;
}
@@ -868,3 +889,106 @@ int afs_launder_page(struct page *page)
ClearPagePrivate(page);
return ret;
}
+
+/*
+ * Clear the PG_fscache flag from a sequence of pages and wake up anyone who's
+ * waiting. The last page is included in the sequence.
+ */
+static void afs_clear_fscache_bits(struct address_space *mapping,
+ pgoff_t start, pgoff_t last)
+{
+ struct page *page;
+
+ XA_STATE(xas, &mapping->i_pages, start);
+
+ rcu_read_lock();
+ xas_for_each(&xas, page, last) {
+ unlock_page_fscache(page);
+ }
+ rcu_read_unlock();
+}
+
+/*
+ * Deal with the completion of writing the data to the cache.
+ */
+static void afs_write_to_cache_done(struct fscache_io_request *_req)
+{
+ struct afs_read *req = container_of(_req, struct afs_read, cache);
+ pgoff_t index = req->cache.pos >> PAGE_SHIFT;
+ pgoff_t last = index + req->cache.nr_pages - 1;
+
+ _enter("%lx,%x,%llx", index, req->cache.nr_pages, req->cache.transferred);
+
+ afs_clear_fscache_bits(req->cache.mapping, index, last);
+
+ if (req->cache.error && req->cache.error != -ENOBUFS) {
+ struct afs_vnode *vnode = req->vnode;
+ struct afs_vnode_cache_aux aux = {
+ .data_version = vnode->status.data_version,
+ };
+ _debug("inval wr %d", req->cache.error);
+ fscache_invalidate(req->cache.cookie, &aux,
+ i_size_read(&vnode->vfs_inode), 0);
+ }
+}
+
+static const struct fscache_io_request_ops afs_write_req_ops = {
+ .get = afs_req_get,
+ .put = afs_req_put,
+};
+
+/*
+ * Save the write to the cache also.
+ */
+static void afs_write_to_cache(struct afs_vnode *vnode,
+ pgoff_t start, pgoff_t last, loff_t a, loff_t b)
+{
+ struct afs_read *req;
+ struct iov_iter iter;
+
+ struct fscache_request_shape shape = {
+ .proposed_start = start,
+ .proposed_nr_pages = last - start + 1,
+ .max_io_pages = UINT_MAX,
+ .i_size = i_size_read(&vnode->vfs_inode),
+ .for_write = true,
+ };
+
+ _enter("%lx,%lx,%llx,%llx", start, last, a, b);
+
+ fscache_shape_request(afs_vnode_cache(vnode), &shape);
+ if (!(shape.to_be_done & FSCACHE_WRITE_TO_CACHE) ||
+ shape.actual_nr_pages == 0 ||
+ shape.actual_start != start)
+ goto abandon;
+
+ if (shape.actual_nr_pages < shape.proposed_nr_pages) {
+ afs_clear_fscache_bits(vnode->vfs_inode.i_mapping,
+ start + shape.actual_nr_pages,
+ start + shape.proposed_nr_pages - 1);
+ last = start + shape.actual_nr_pages - 1;
+ b = (loff_t)(last + 1) << PAGE_SHIFT;
+ }
+
+ req = afs_alloc_read(GFP_NOFS);
+ if (!req)
+ goto abandon;
+
+ fscache_init_io_request(&req->cache, afs_vnode_cache(vnode),
+ &afs_write_req_ops);
+ req->vnode = vnode;
+ req->cache.pos = round_down(a, shape.dio_block_size);
+ req->cache.len = round_up(b, shape.dio_block_size) - req->cache.pos;
+ req->cache.nr_pages = shape.actual_nr_pages;
+ req->cache.mapping = vnode->vfs_inode.i_mapping;
+ req->cache.io_done = &afs_write_to_cache_done;
+
+ iov_iter_mapping(&iter, WRITE, req->cache.mapping,
+ req->cache.pos, req->cache.len);
+ fscache_write(&req->cache, &iter);
+ afs_put_read(req);
+ return;
+
+abandon:
+ afs_clear_fscache_bits(vnode->vfs_inode.i_mapping, start, last);
+}

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