9p: Convert to using the netfs helper lib to do reads and caching

Convert the 9p filesystem to use the netfs helper lib to handle readpage,
readahead and write_begin, converting those into a common issue_op for the
filesystem itself to handle.  The netfs helper lib also handles reading
from fscache if a cache is available, and interleaving reads from both
sources.

This change also switches from the old fscache I/O API to the new one,
meaning that fscache no longer keeps track of netfs pages and instead does
async DIO between the backing files and the 9p file pagecache.  As a part
of this change, the handling of PG_fscache changes.  It now just means that
the cache has a write I/O operation in progress on a page (PG_locked
is used for a read I/O op).

Note that this is a cut-down version of the fscache rewrite and does not
change any of the cookie and cache coherency handling.

Changes
=======
ver #4:
  - Rebase on top of folios.
  - Don't use wait_on_page_bit_killable().

ver #3:
  - v9fs_req_issue_op() needs to terminate the subrequest.
  - v9fs_write_end() needs to call SetPageUptodate() a bit more often.
  - It's not CONFIG_{AFS,V9FS}_FSCACHE[1]
  - v9fs_init_rreq() should take a ref on the p9_fid and the cleanup should
    drop it [from Dominique Martinet].

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-and-tested-by: Dominique Martinet <asmadeus@codewreck.org>
cc: v9fs-developer@lists.sourceforge.net
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/YUm+xucHxED+1MJp@codewreck.org/ [1]
Link: https://lore.kernel.org/r/163162772646.438332.16323773205855053535.stgit@warthog.procyon.org.uk/ # rfc
Link: https://lore.kernel.org/r/163189109885.2509237.7153668924503399173.stgit@warthog.procyon.org.uk/ # rfc v2
Link: https://lore.kernel.org/r/163363943896.1980952.1226527304649419689.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/163551662876.1877519.14706391695553204156.stgit@warthog.procyon.org.uk/ # v4
Link: https://lore.kernel.org/r/163584179557.4023316.11089762304657644342.stgit@warthog.procyon.org.uk # rebase on folio
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>

1 files changed, 0 insertions, 137 deletions

diff --git a/fs/9p/cache.c b/fs/9p/cache.c
index 1769a44f4819..077f0a40aa01 100644
--- a/fs/9p/cache.c
+++ b/fs/9p/cache.c
@@ -199,140 +199,3 @@ void v9fs_cache_inode_reset_cookie(struct inode *inode)
 
 	mutex_unlock(&v9inode->fscache_lock);
 }
-
-int __v9fs_fscache_release_page(struct page *page, gfp_t gfp)
-{
-	struct inode *inode = page->mapping->host;
-	struct v9fs_inode *v9inode = V9FS_I(inode);
-
-	BUG_ON(!v9inode->fscache);
-
-	return fscache_maybe_release_page(v9inode->fscache, page, gfp);
-}
-
-void __v9fs_fscache_invalidate_page(struct page *page)
-{
-	struct inode *inode = page->mapping->host;
-	struct v9fs_inode *v9inode = V9FS_I(inode);
-
-	BUG_ON(!v9inode->fscache);
-
-	if (PageFsCache(page)) {
-		fscache_wait_on_page_write(v9inode->fscache, page);
-		BUG_ON(!PageLocked(page));
-		fscache_uncache_page(v9inode->fscache, page);
-	}
-}
-
-static void v9fs_vfs_readpage_complete(struct page *page, void *data,
-				       int error)
-{
-	if (!error)
-		SetPageUptodate(page);
-
-	unlock_page(page);
-}
-
-/*
- * __v9fs_readpage_from_fscache - read a page from cache
- *
- * Returns 0 if the pages are in cache and a BIO is submitted,
- * 1 if the pages are not in cache and -error otherwise.
- */
-
-int __v9fs_readpage_from_fscache(struct inode *inode, struct page *page)
-{
-	int ret;
-	const struct v9fs_inode *v9inode = V9FS_I(inode);
-
-	p9_debug(P9_DEBUG_FSC, "inode %p page %p\n", inode, page);
-	if (!v9inode->fscache)
-		return -ENOBUFS;
-
-	ret = fscache_read_or_alloc_page(v9inode->fscache,
-					 page,
-					 v9fs_vfs_readpage_complete,
-					 NULL,
-					 GFP_KERNEL);
-	switch (ret) {
-	case -ENOBUFS:
-	case -ENODATA:
-		p9_debug(P9_DEBUG_FSC, "page/inode not in cache %d\n", ret);
-		return 1;
-	case 0:
-		p9_debug(P9_DEBUG_FSC, "BIO submitted\n");
-		return ret;
-	default:
-		p9_debug(P9_DEBUG_FSC, "ret %d\n", ret);
-		return ret;
-	}
-}
-
-/*
- * __v9fs_readpages_from_fscache - read multiple pages from cache
- *
- * Returns 0 if the pages are in cache and a BIO is submitted,
- * 1 if the pages are not in cache and -error otherwise.
- */
-
-int __v9fs_readpages_from_fscache(struct inode *inode,
-				  struct address_space *mapping,
-				  struct list_head *pages,
-				  unsigned *nr_pages)
-{
-	int ret;
-	const struct v9fs_inode *v9inode = V9FS_I(inode);
-
-	p9_debug(P9_DEBUG_FSC, "inode %p pages %u\n", inode, *nr_pages);
-	if (!v9inode->fscache)
-		return -ENOBUFS;
-
-	ret = fscache_read_or_alloc_pages(v9inode->fscache,
-					  mapping, pages, nr_pages,
-					  v9fs_vfs_readpage_complete,
-					  NULL,
-					  mapping_gfp_mask(mapping));
-	switch (ret) {
-	case -ENOBUFS:
-	case -ENODATA:
-		p9_debug(P9_DEBUG_FSC, "pages/inodes not in cache %d\n", ret);
-		return 1;
-	case 0:
-		BUG_ON(!list_empty(pages));
-		BUG_ON(*nr_pages != 0);
-		p9_debug(P9_DEBUG_FSC, "BIO submitted\n");
-		return ret;
-	default:
-		p9_debug(P9_DEBUG_FSC, "ret %d\n", ret);
-		return ret;
-	}
-}
-
-/*
- * __v9fs_readpage_to_fscache - write a page to the cache
- *
- */
-
-void __v9fs_readpage_to_fscache(struct inode *inode, struct page *page)
-{
-	int ret;
-	const struct v9fs_inode *v9inode = V9FS_I(inode);
-
-	p9_debug(P9_DEBUG_FSC, "inode %p page %p\n", inode, page);
-	ret = fscache_write_page(v9inode->fscache, page,
-				 i_size_read(&v9inode->vfs_inode), GFP_KERNEL);
-	p9_debug(P9_DEBUG_FSC, "ret =  %d\n", ret);
-	if (ret != 0)
-		v9fs_uncache_page(inode, page);
-}
-
-/*
- * wait for a page to complete writing to the cache
- */
-void __v9fs_fscache_wait_on_page_write(struct inode *inode, struct page *page)
-{
-	const struct v9fs_inode *v9inode = V9FS_I(inode);
-	p9_debug(P9_DEBUG_FSC, "inode %p page %p\n", inode, page);
-	if (PageFsCache(page))
-		fscache_wait_on_page_write(v9inode->fscache, page);
-}