fs/9p: remove writeback fid and fix per-file modes

This patch removes the creating of an additional writeback_fid
for opened files.  The patch addresses problems when files
were opened write-only or getattr on files with dirty caches.

This patch also incorporates information about cache behavior
in the fid for every file.  This allows us to reflect cache
behavior from mount flags, open mode, and information from
the server to inform readahead and writeback behavior.

This includes adding support for a 9p semantic that qid.version==0
is used to mark a file as non-cachable which is important for
synthetic files.  This may have a side-effect of not supporting
caching on certain legacy file servers that do not properly set
qid.version.  There is also now a mount flag which can disable
the qid.version behavior.

Signed-off-by: Eric Van Hensbergen <ericvh@kernel.org>

1 files changed, 19 insertions, 29 deletions

diff --git a/fs/9p/vfs_inode_dotl.c b/fs/9p/vfs_inode_dotl.c
index a28eb3aeab29..4b9488cb7a56 100644
--- a/fs/9p/vfs_inode_dotl.c
+++ b/fs/9p/vfs_inode_dotl.c
@@ -232,12 +232,12 @@ v9fs_vfs_atomic_open_dotl(struct inode *dir, struct dentry *dentry,
 	int err = 0;
 	kgid_t gid;
 	umode_t mode;
+	int p9_omode = v9fs_open_to_dotl_flags(flags);
 	const unsigned char *name = NULL;
 	struct p9_qid qid;
 	struct inode *inode;
 	struct p9_fid *fid = NULL;
-	struct v9fs_inode *v9inode;
-	struct p9_fid *dfid = NULL, *ofid = NULL, *inode_fid = NULL;
+	struct p9_fid *dfid = NULL, *ofid = NULL;
 	struct v9fs_session_info *v9ses;
 	struct posix_acl *pacl = NULL, *dacl = NULL;
 	struct dentry *res = NULL;
@@ -282,14 +282,19 @@ v9fs_vfs_atomic_open_dotl(struct inode *dir, struct dentry *dentry,
 	/* Update mode based on ACL value */
 	err = v9fs_acl_mode(dir, &mode, &dacl, &pacl);
 	if (err) {
-		p9_debug(P9_DEBUG_VFS, "Failed to get acl values in creat %d\n",
+		p9_debug(P9_DEBUG_VFS, "Failed to get acl values in create %d\n",
 			 err);
 		goto out;
 	}
-	err = p9_client_create_dotl(ofid, name, v9fs_open_to_dotl_flags(flags),
-				    mode, gid, &qid);
+
+	if ((v9ses->cache >= CACHE_WRITEBACK) && (p9_omode & P9_OWRITE)) {
+		p9_omode = (p9_omode & !P9_OWRITE) | P9_ORDWR;
+		p9_debug(P9_DEBUG_CACHE,
+			"write-only file with writeback enabled, creating w/ O_RDWR\n");
+	}
+	err = p9_client_create_dotl(ofid, name, p9_omode, mode, gid, &qid);
 	if (err < 0) {
-		p9_debug(P9_DEBUG_VFS, "p9_client_open_dotl failed in creat %d\n",
+		p9_debug(P9_DEBUG_VFS, "p9_client_open_dotl failed in create %d\n",
 			 err);
 		goto out;
 	}
@@ -314,36 +319,19 @@ v9fs_vfs_atomic_open_dotl(struct inode *dir, struct dentry *dentry,
 	v9fs_fid_add(dentry, &fid);
 	d_instantiate(dentry, inode);
 
-	v9inode = V9FS_I(inode);
-	mutex_lock(&v9inode->v_mutex);
-	if ((v9ses->cache) && !v9inode->writeback_fid &&
-	    ((flags & O_ACCMODE) != O_RDONLY)) {
-		/*
-		 * clone a fid and add it to writeback_fid
-		 * we do it during open time instead of
-		 * page dirty time via write_begin/page_mkwrite
-		 * because we want write after unlink usecase
-		 * to work.
-		 */
-		inode_fid = v9fs_writeback_fid(dentry);
-		if (IS_ERR(inode_fid)) {
-			err = PTR_ERR(inode_fid);
-			mutex_unlock(&v9inode->v_mutex);
-			goto out;
-		}
-		v9inode->writeback_fid = (void *) inode_fid;
-	}
-	mutex_unlock(&v9inode->v_mutex);
 	/* Since we are opening a file, assign the open fid to the file */
 	err = finish_open(file, dentry, generic_file_open);
 	if (err)
 		goto out;
 	file->private_data = ofid;
 #ifdef CONFIG_9P_FSCACHE
-	if (v9ses->cache == CACHE_FSCACHE)
+	if (v9ses->cache == CACHE_FSCACHE) {
+		struct v9fs_inode *v9inode = V9FS_I(inode);
 		fscache_use_cookie(v9fs_inode_cookie(v9inode),
 				   file->f_mode & FMODE_WRITE);
+	}
 #endif
+	v9fs_fid_add_modes(ofid, v9ses->flags, v9ses->cache, flags);
 	v9fs_open_fid_add(inode, &ofid);
 	file->f_mode |= FMODE_CREATED;
 out:
@@ -464,9 +452,9 @@ v9fs_vfs_getattr_dotl(struct mnt_idmap *idmap,
 	p9_debug(P9_DEBUG_VFS, "dentry: %p\n", dentry);
 	v9ses = v9fs_dentry2v9ses(dentry);
 	if (v9ses->cache == CACHE_LOOSE || v9ses->cache == CACHE_FSCACHE) {
-		generic_fillattr(&nop_mnt_idmap, d_inode(dentry), stat);
+		generic_fillattr(&nop_mnt_idmap, inode, stat);
 		return 0;
-	} else if (v9ses->cache >= CACHE_WRITEBACK) {
+	} else if (v9ses->cache) {
 		if (S_ISREG(inode->i_mode)) {
 			int retval = filemap_fdatawrite(inode->i_mapping);
 
@@ -613,6 +601,8 @@ int v9fs_vfs_setattr_dotl(struct mnt_idmap *idmap,
 	if ((iattr->ia_valid & ATTR_SIZE) && iattr->ia_size !=
 		 i_size_read(inode)) {
 		truncate_setsize(inode, iattr->ia_size);
+		truncate_pagecache(inode, iattr->ia_size);
+
 		if (v9ses->cache == CACHE_FSCACHE)
 			fscache_resize_cookie(v9fs_inode_cookie(v9inode), iattr->ia_size);
 	}