nilfs2: avoid rec_len overflow with 64KB block size

With 64KB blocksize, a directory entry can have size 64KB which does
not fit into 16 bits we have for entry length.  So this patch stores
0xffff instead and converts value when read from / written to disk.

Nilfs derives its directory implementation from ext2 filesystem, and
this draws upon the corresponding change on ext2.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

2 files changed, 32 insertions, 12 deletions

diff --git a/fs/nilfs2/dir.c b/fs/nilfs2/dir.c
index d8d183e6d095..b60277b44468 100644
--- a/fs/nilfs2/dir.c
+++ b/fs/nilfs2/dir.c
@@ -141,7 +141,7 @@ static void nilfs_check_page(struct page *page)
         }
         for (offs = 0; offs <= limit - NILFS_DIR_REC_LEN(1); offs += rec_len) {
                 p = (struct nilfs_dir_entry *)(kaddr + offs);
-                rec_len = le16_to_cpu(p->rec_len);
+                rec_len = nilfs_rec_len_from_disk(p->rec_len);
 
                 if (rec_len < NILFS_DIR_REC_LEN(1))
                         goto Eshort;
@@ -235,7 +235,8 @@ nilfs_match(int len, const unsigned char *name, struct nilfs_dir_entry *de)
  */
 static struct nilfs_dir_entry *nilfs_next_entry(struct nilfs_dir_entry *p)
 {
-        return (struct nilfs_dir_entry *)((char *)p + le16_to_cpu(p->rec_len));
+        return (struct nilfs_dir_entry *)((char *)p +
+                                          nilfs_rec_len_from_disk(p->rec_len));
 }
 
 static unsigned char
@@ -326,7 +327,7 @@ static int nilfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
                                         goto success;
                                 }
                         }
-                        filp->f_pos += le16_to_cpu(de->rec_len);
+                        filp->f_pos += nilfs_rec_len_from_disk(de->rec_len);
                 }
                 nilfs_put_page(page);
         }
@@ -441,7 +442,7 @@ void nilfs_set_link(struct inode *dir, struct nilfs_dir_entry *de,
                     struct page *page, struct inode *inode)
 {
         unsigned from = (char *) de - (char *) page_address(page);
-        unsigned to = from + le16_to_cpu(de->rec_len);
+        unsigned to = from + nilfs_rec_len_from_disk(de->rec_len);
         struct address_space *mapping = page->mapping;
         int err;
 
@@ -497,7 +498,7 @@ int nilfs_add_link(struct dentry *dentry, struct inode *inode)
                                 /* We hit i_size */
                                 name_len = 0;
                                 rec_len = chunk_size;
-                                de->rec_len = cpu_to_le16(chunk_size);
+                                de->rec_len = nilfs_rec_len_to_disk(chunk_size);
                                 de->inode = 0;
                                 goto got_it;
                         }
@@ -511,7 +512,7 @@ int nilfs_add_link(struct dentry *dentry, struct inode *inode)
                         if (nilfs_match(namelen, name, de))
                                 goto out_unlock;
                         name_len = NILFS_DIR_REC_LEN(de->name_len);
-                        rec_len = le16_to_cpu(de->rec_len);
+                        rec_len = nilfs_rec_len_from_disk(de->rec_len);
                         if (!de->inode && rec_len >= reclen)
                                 goto got_it;
                         if (rec_len >= name_len + reclen)
@@ -534,8 +535,8 @@ got_it:
                 struct nilfs_dir_entry *de1;
 
                 de1 = (struct nilfs_dir_entry *)((char *)de + name_len);
-                de1->rec_len = cpu_to_le16(rec_len - name_len);
-                de->rec_len = cpu_to_le16(name_len);
+                de1->rec_len = nilfs_rec_len_to_disk(rec_len - name_len);
+                de->rec_len = nilfs_rec_len_to_disk(name_len);
                 de = de1;
         }
         de->name_len = namelen;
@@ -566,7 +567,8 @@ int nilfs_delete_entry(struct nilfs_dir_entry *dir, struct page *page)
         struct inode *inode = mapping->host;
         char *kaddr = page_address(page);
         unsigned from = ((char *)dir - kaddr) & ~(nilfs_chunk_size(inode) - 1);
-        unsigned to = ((char *)dir - kaddr) + le16_to_cpu(dir->rec_len);
+        unsigned to = ((char *)dir - kaddr) +
+                nilfs_rec_len_from_disk(dir->rec_len);
         struct nilfs_dir_entry *pde = NULL;
         struct nilfs_dir_entry *de = (struct nilfs_dir_entry *)(kaddr + from);
         int err;
@@ -587,7 +589,7 @@ int nilfs_delete_entry(struct nilfs_dir_entry *dir, struct page *page)
         err = nilfs_prepare_chunk(page, mapping, from, to);
         BUG_ON(err);
         if (pde)
-                pde->rec_len = cpu_to_le16(to - from);
+                pde->rec_len = nilfs_rec_len_to_disk(to - from);
         dir->inode = 0;
         nilfs_commit_chunk(page, mapping, from, to);
         inode->i_ctime = inode->i_mtime = CURRENT_TIME;
@@ -621,14 +623,14 @@ int nilfs_make_empty(struct inode *inode, struct inode *parent)
         memset(kaddr, 0, chunk_size);
         de = (struct nilfs_dir_entry *)kaddr;
         de->name_len = 1;
-        de->rec_len = cpu_to_le16(NILFS_DIR_REC_LEN(1));
+        de->rec_len = nilfs_rec_len_to_disk(NILFS_DIR_REC_LEN(1));
         memcpy(de->name, ".\0\0", 4);
         de->inode = cpu_to_le64(inode->i_ino);
         nilfs_set_de_type(de, inode);
 
         de = (struct nilfs_dir_entry *)(kaddr + NILFS_DIR_REC_LEN(1));
         de->name_len = 2;
-        de->rec_len = cpu_to_le16(chunk_size - NILFS_DIR_REC_LEN(1));
+        de->rec_len = nilfs_rec_len_to_disk(chunk_size - NILFS_DIR_REC_LEN(1));
         de->inode = cpu_to_le64(parent->i_ino);
         memcpy(de->name, "..\0", 4);
         nilfs_set_de_type(de, inode);
diff --git a/include/linux/nilfs2_fs.h b/include/linux/nilfs2_fs.h
index 7dd4cd494490..970828a5ffc5 100644
--- a/include/linux/nilfs2_fs.h
+++ b/include/linux/nilfs2_fs.h
@@ -326,7 +326,25 @@ enum {
 #define NILFS_DIR_ROUND                 (NILFS_DIR_PAD - 1)
 #define NILFS_DIR_REC_LEN(name_len)     (((name_len) + 12 + NILFS_DIR_ROUND) & \
                                         ~NILFS_DIR_ROUND)
+#define NILFS_MAX_REC_LEN               ((1<<16)-1)
 
+static inline unsigned nilfs_rec_len_from_disk(__le16 dlen)
+{
+        unsigned len = le16_to_cpu(dlen);
+
+        if (len == NILFS_MAX_REC_LEN)
+                return 1 << 16;
+        return len;
+}
+
+static inline __le16 nilfs_rec_len_to_disk(unsigned len)
+{
+        if (len == (1 << 16))
+                return cpu_to_le16(NILFS_MAX_REC_LEN);
+        else if (len > (1 << 16))
+                BUG();
+        return cpu_to_le16(len);
+}
 
 /**
  * struct nilfs_finfo - file information