hfsplus: implement attributes file creation functionality

Implement functionality of creation AttributesFile metadata file on HFS+
volume in the case of absence of it.

It makes trying to open AttributesFile's B-tree during mount of HFS+
volume.  If HFS+ volume hasn't AttributesFile then a pointer on
AttributesFile's B-tree keeps as NULL.  Thereby, when it is discovered
absence of AttributesFile on HFS+ volume in the begin of xattr creation
operation then AttributesFile will be created.

The creation of AttributesFile will have success in the case of
availability (2 * clump) free blocks on HFS+ volume.  Otherwise,
creation operation is ended with error (-ENOSPC).

Signed-off-by: Vyacheslav Dubeyko <slava@dubeyko.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@infradead.org>
Acked-by: Hin-Tak Leung <htl10@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 140 insertions, 2 deletions

diff --git a/fs/hfsplus/xattr.c b/fs/hfsplus/xattr.c
index 568a45cb1145..efc85b1377cc 100644
--- a/fs/hfsplus/xattr.c
+++ b/fs/hfsplus/xattr.c
@@ -192,6 +192,143 @@ static void hfsplus_init_header_node(struct inode *attr_file,
         *--rec_offsets = cpu_to_be16(offset);
 }
 
+static int hfsplus_create_attributes_file(struct super_block *sb)
+{
+        int err = 0;
+        struct hfsplus_sb_info *sbi = HFSPLUS_SB(sb);
+        struct inode *attr_file;
+        struct hfsplus_inode_info *hip;
+        u32 clump_size;
+        u16 node_size = HFSPLUS_ATTR_TREE_NODE_SIZE;
+        char *buf;
+        int index, written;
+        struct address_space *mapping;
+        struct page *page;
+        int old_state = HFSPLUS_EMPTY_ATTR_TREE;
+
+        hfs_dbg(ATTR_MOD, "create_attr_file: ino %d\n", HFSPLUS_ATTR_CNID);
+
+check_attr_tree_state_again:
+        switch (atomic_read(&sbi->attr_tree_state)) {
+        case HFSPLUS_EMPTY_ATTR_TREE:
+                if (old_state != atomic_cmpxchg(&sbi->attr_tree_state,
+                                                old_state,
+                                                HFSPLUS_CREATING_ATTR_TREE))
+                        goto check_attr_tree_state_again;
+                break;
+        case HFSPLUS_CREATING_ATTR_TREE:
+                /*
+                 * This state means that another thread is in process
+                 * of AttributesFile creation. Theoretically, it is
+                 * possible to be here. But really __setxattr() method
+                 * first of all calls hfs_find_init() for lookup in
+                 * B-tree of CatalogFile. This method locks mutex of
+                 * CatalogFile's B-tree. As a result, if some thread
+                 * is inside AttributedFile creation operation then
+                 * another threads will be waiting unlocking of
+                 * CatalogFile's B-tree's mutex. However, if code will
+                 * change then we will return error code (-EAGAIN) from
+                 * here. Really, it means that first try to set of xattr
+                 * fails with error but second attempt will have success.
+                 */
+                return -EAGAIN;
+        case HFSPLUS_VALID_ATTR_TREE:
+                return 0;
+        case HFSPLUS_FAILED_ATTR_TREE:
+                return -EOPNOTSUPP;
+        default:
+                BUG();
+        }
+
+        attr_file = hfsplus_iget(sb, HFSPLUS_ATTR_CNID);
+        if (IS_ERR(attr_file)) {
+                pr_err("failed to load attributes file\n");
+                return PTR_ERR(attr_file);
+        }
+
+        BUG_ON(i_size_read(attr_file) != 0);
+
+        hip = HFSPLUS_I(attr_file);
+
+        clump_size = hfsplus_calc_btree_clump_size(sb->s_blocksize,
+                                                    node_size,
+                                                    sbi->sect_count,
+                                                    HFSPLUS_ATTR_CNID);
+
+        mutex_lock(&hip->extents_lock);
+        hip->clump_blocks = clump_size >> sbi->alloc_blksz_shift;
+        mutex_unlock(&hip->extents_lock);
+
+        if (sbi->free_blocks <= (hip->clump_blocks << 1)) {
+                err = -ENOSPC;
+                goto end_attr_file_creation;
+        }
+
+        while (hip->alloc_blocks < hip->clump_blocks) {
+                err = hfsplus_file_extend(attr_file);
+                if (unlikely(err)) {
+                        pr_err("failed to extend attributes file\n");
+                        goto end_attr_file_creation;
+                }
+                hip->phys_size = attr_file->i_size =
+                        (loff_t)hip->alloc_blocks << sbi->alloc_blksz_shift;
+                hip->fs_blocks = hip->alloc_blocks << sbi->fs_shift;
+                inode_set_bytes(attr_file, attr_file->i_size);
+        }
+
+        buf = kzalloc(node_size, GFP_NOFS);
+        if (!buf) {
+                pr_err("failed to allocate memory for header node\n");
+                err = -ENOMEM;
+                goto end_attr_file_creation;
+        }
+
+        hfsplus_init_header_node(attr_file, clump_size, buf, node_size);
+
+        mapping = attr_file->i_mapping;
+
+        index = 0;
+        written = 0;
+        for (; written < node_size; index++, written += PAGE_CACHE_SIZE) {
+                void *kaddr;
+
+                page = read_mapping_page(mapping, index, NULL);
+                if (IS_ERR(page)) {
+                        err = PTR_ERR(page);
+                        goto failed_header_node_init;
+                }
+
+                kaddr = kmap_atomic(page);
+                memcpy(kaddr, buf + written,
+                        min_t(size_t, PAGE_CACHE_SIZE, node_size - written));
+                kunmap_atomic(kaddr);
+
+                set_page_dirty(page);
+                page_cache_release(page);
+        }
+
+        hfsplus_mark_inode_dirty(attr_file, HFSPLUS_I_ATTR_DIRTY);
+
+        sbi->attr_tree = hfs_btree_open(sb, HFSPLUS_ATTR_CNID);
+        if (!sbi->attr_tree)
+                pr_err("failed to load attributes file\n");
+
+failed_header_node_init:
+        kfree(buf);
+
+end_attr_file_creation:
+        iput(attr_file);
+
+        if (!err)
+                atomic_set(&sbi->attr_tree_state, HFSPLUS_VALID_ATTR_TREE);
+        else if (err == -ENOSPC)
+                atomic_set(&sbi->attr_tree_state, HFSPLUS_EMPTY_ATTR_TREE);
+        else
+                atomic_set(&sbi->attr_tree_state, HFSPLUS_FAILED_ATTR_TREE);
+
+        return err;
+}
+
 int __hfsplus_setxattr(struct inode *inode, const char *name,
                         const void *value, size_t size, int flags)
 {
@@ -276,8 +413,9 @@ int __hfsplus_setxattr(struct inode *inode, const char *name,
         }
 
         if (!HFSPLUS_SB(inode->i_sb)->attr_tree) {
-                err = -EOPNOTSUPP;
-                goto end_setxattr;
+                err = hfsplus_create_attributes_file(inode->i_sb);
+                if (unlikely(err))
+                        goto end_setxattr;
         }
 
         if (hfsplus_attr_exists(inode, name)) {