ext4: return 32/64-bit dir name hash according to usage type
Traditionally ext2/3/4 has returned a 32-bit hash value from llseek()
to appease NFSv2, which can only handle a 32-bit cookie for seekdir()
and telldir(). However, this causes problems if there are 32-bit hash
collisions, since the NFSv2 server can get stuck resending the same
entries from the directory repeatedly.
Allow ext4 to return a full 64-bit hash (both major and minor) for
telldir to decrease the chance of hash collisions. This still needs
integration on the NFS side.
Patch-updated-by: Bernd Schubert <bernd.schubert@itwm.fraunhofer.de>
(blame me if something is not correct)
Signed-off-by: Fan Yong <yong.fan@whamcloud.com>
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Signed-off-by: Bernd Schubert <bernd.schubert@itwm.fraunhofer.de>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c
index 164c560..689d1b1 100644
--- a/fs/ext4/dir.c
+++ b/fs/ext4/dir.c
@@ -32,24 +32,8 @@
DT_UNKNOWN, DT_REG, DT_DIR, DT_CHR, DT_BLK, DT_FIFO, DT_SOCK, DT_LNK
};
-static int ext4_readdir(struct file *, void *, filldir_t);
static int ext4_dx_readdir(struct file *filp,
void *dirent, filldir_t filldir);
-static int ext4_release_dir(struct inode *inode,
- struct file *filp);
-
-const struct file_operations ext4_dir_operations = {
- .llseek = ext4_llseek,
- .read = generic_read_dir,
- .readdir = ext4_readdir, /* we take BKL. needed?*/
- .unlocked_ioctl = ext4_ioctl,
-#ifdef CONFIG_COMPAT
- .compat_ioctl = ext4_compat_ioctl,
-#endif
- .fsync = ext4_sync_file,
- .release = ext4_release_dir,
-};
-
static unsigned char get_dtype(struct super_block *sb, int filetype)
{
@@ -60,6 +44,26 @@
return (ext4_filetype_table[filetype]);
}
+/**
+ * Check if the given dir-inode refers to an htree-indexed directory
+ * (or a directory which chould potentially get coverted to use htree
+ * indexing).
+ *
+ * Return 1 if it is a dx dir, 0 if not
+ */
+static int is_dx_dir(struct inode *inode)
+{
+ struct super_block *sb = inode->i_sb;
+
+ if (EXT4_HAS_COMPAT_FEATURE(inode->i_sb,
+ EXT4_FEATURE_COMPAT_DIR_INDEX) &&
+ ((ext4_test_inode_flag(inode, EXT4_INODE_INDEX)) ||
+ ((inode->i_size >> sb->s_blocksize_bits) == 1)))
+ return 1;
+
+ return 0;
+}
+
/*
* Return 0 if the directory entry is OK, and 1 if there is a problem
*
@@ -115,18 +119,13 @@
unsigned int offset;
int i, stored;
struct ext4_dir_entry_2 *de;
- struct super_block *sb;
int err;
struct inode *inode = filp->f_path.dentry->d_inode;
+ struct super_block *sb = inode->i_sb;
int ret = 0;
int dir_has_error = 0;
- sb = inode->i_sb;
-
- if (EXT4_HAS_COMPAT_FEATURE(inode->i_sb,
- EXT4_FEATURE_COMPAT_DIR_INDEX) &&
- ((ext4_test_inode_flag(inode, EXT4_INODE_INDEX)) ||
- ((inode->i_size >> sb->s_blocksize_bits) == 1))) {
+ if (is_dx_dir(inode)) {
err = ext4_dx_readdir(filp, dirent, filldir);
if (err != ERR_BAD_DX_DIR) {
ret = err;
@@ -254,22 +253,134 @@
return ret;
}
+static inline int is_32bit_api(void)
+{
+#ifdef CONFIG_COMPAT
+ return is_compat_task();
+#else
+ return (BITS_PER_LONG == 32);
+#endif
+}
+
/*
* These functions convert from the major/minor hash to an f_pos
- * value.
+ * value for dx directories
*
- * Currently we only use major hash numer. This is unfortunate, but
- * on 32-bit machines, the same VFS interface is used for lseek and
- * llseek, so if we use the 64 bit offset, then the 32-bit versions of
- * lseek/telldir/seekdir will blow out spectacularly, and from within
- * the ext2 low-level routine, we don't know if we're being called by
- * a 64-bit version of the system call or the 32-bit version of the
- * system call. Worse yet, NFSv2 only allows for a 32-bit readdir
- * cookie. Sigh.
+ * Upper layer (for example NFS) should specify FMODE_32BITHASH or
+ * FMODE_64BITHASH explicitly. On the other hand, we allow ext4 to be mounted
+ * directly on both 32-bit and 64-bit nodes, under such case, neither
+ * FMODE_32BITHASH nor FMODE_64BITHASH is specified.
*/
-#define hash2pos(major, minor) (major >> 1)
-#define pos2maj_hash(pos) ((pos << 1) & 0xffffffff)
-#define pos2min_hash(pos) (0)
+static inline loff_t hash2pos(struct file *filp, __u32 major, __u32 minor)
+{
+ if ((filp->f_mode & FMODE_32BITHASH) ||
+ (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
+ return major >> 1;
+ else
+ return ((__u64)(major >> 1) << 32) | (__u64)minor;
+}
+
+static inline __u32 pos2maj_hash(struct file *filp, loff_t pos)
+{
+ if ((filp->f_mode & FMODE_32BITHASH) ||
+ (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
+ return (pos << 1) & 0xffffffff;
+ else
+ return ((pos >> 32) << 1) & 0xffffffff;
+}
+
+static inline __u32 pos2min_hash(struct file *filp, loff_t pos)
+{
+ if ((filp->f_mode & FMODE_32BITHASH) ||
+ (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
+ return 0;
+ else
+ return pos & 0xffffffff;
+}
+
+/*
+ * Return 32- or 64-bit end-of-file for dx directories
+ */
+static inline loff_t ext4_get_htree_eof(struct file *filp)
+{
+ if ((filp->f_mode & FMODE_32BITHASH) ||
+ (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
+ return EXT4_HTREE_EOF_32BIT;
+ else
+ return EXT4_HTREE_EOF_64BIT;
+}
+
+
+/*
+ * ext4_dir_llseek() based on generic_file_llseek() to handle both
+ * non-htree and htree directories, where the "offset" is in terms
+ * of the filename hash value instead of the byte offset.
+ *
+ * NOTE: offsets obtained *before* ext4_set_inode_flag(dir, EXT4_INODE_INDEX)
+ * will be invalid once the directory was converted into a dx directory
+ */
+loff_t ext4_dir_llseek(struct file *file, loff_t offset, int origin)
+{
+ struct inode *inode = file->f_mapping->host;
+ loff_t ret = -EINVAL;
+ int dx_dir = is_dx_dir(inode);
+
+ mutex_lock(&inode->i_mutex);
+
+ /* NOTE: relative offsets with dx directories might not work
+ * as expected, as it is difficult to figure out the
+ * correct offset between dx hashes */
+
+ switch (origin) {
+ case SEEK_END:
+ if (unlikely(offset > 0))
+ goto out_err; /* not supported for directories */
+
+ /* so only negative offsets are left, does that have a
+ * meaning for directories at all? */
+ if (dx_dir)
+ offset += ext4_get_htree_eof(file);
+ else
+ offset += inode->i_size;
+ break;
+ case SEEK_CUR:
+ /*
+ * Here we special-case the lseek(fd, 0, SEEK_CUR)
+ * position-querying operation. Avoid rewriting the "same"
+ * f_pos value back to the file because a concurrent read(),
+ * write() or lseek() might have altered it
+ */
+ if (offset == 0) {
+ offset = file->f_pos;
+ goto out_ok;
+ }
+
+ offset += file->f_pos;
+ break;
+ }
+
+ if (unlikely(offset < 0))
+ goto out_err;
+
+ if (!dx_dir) {
+ if (offset > inode->i_sb->s_maxbytes)
+ goto out_err;
+ } else if (offset > ext4_get_htree_eof(file))
+ goto out_err;
+
+ /* Special lock needed here? */
+ if (offset != file->f_pos) {
+ file->f_pos = offset;
+ file->f_version = 0;
+ }
+
+out_ok:
+ ret = offset;
+out_err:
+ mutex_unlock(&inode->i_mutex);
+
+ return ret;
+}
/*
* This structure holds the nodes of the red-black tree used to store
@@ -330,15 +441,16 @@
}
-static struct dir_private_info *ext4_htree_create_dir_info(loff_t pos)
+static struct dir_private_info *ext4_htree_create_dir_info(struct file *filp,
+ loff_t pos)
{
struct dir_private_info *p;
p = kzalloc(sizeof(struct dir_private_info), GFP_KERNEL);
if (!p)
return NULL;
- p->curr_hash = pos2maj_hash(pos);
- p->curr_minor_hash = pos2min_hash(pos);
+ p->curr_hash = pos2maj_hash(filp, pos);
+ p->curr_minor_hash = pos2min_hash(filp, pos);
return p;
}
@@ -429,7 +541,7 @@
"null fname?!?\n");
return 0;
}
- curr_pos = hash2pos(fname->hash, fname->minor_hash);
+ curr_pos = hash2pos(filp, fname->hash, fname->minor_hash);
while (fname) {
error = filldir(dirent, fname->name,
fname->name_len, curr_pos,
@@ -454,13 +566,13 @@
int ret;
if (!info) {
- info = ext4_htree_create_dir_info(filp->f_pos);
+ info = ext4_htree_create_dir_info(filp, filp->f_pos);
if (!info)
return -ENOMEM;
filp->private_data = info;
}
- if (filp->f_pos == EXT4_HTREE_EOF)
+ if (filp->f_pos == ext4_get_htree_eof(filp))
return 0; /* EOF */
/* Some one has messed with f_pos; reset the world */
@@ -468,8 +580,8 @@
free_rb_tree_fname(&info->root);
info->curr_node = NULL;
info->extra_fname = NULL;
- info->curr_hash = pos2maj_hash(filp->f_pos);
- info->curr_minor_hash = pos2min_hash(filp->f_pos);
+ info->curr_hash = pos2maj_hash(filp, filp->f_pos);
+ info->curr_minor_hash = pos2min_hash(filp, filp->f_pos);
}
/*
@@ -501,7 +613,7 @@
if (ret < 0)
return ret;
if (ret == 0) {
- filp->f_pos = EXT4_HTREE_EOF;
+ filp->f_pos = ext4_get_htree_eof(filp);
break;
}
info->curr_node = rb_first(&info->root);
@@ -521,7 +633,7 @@
info->curr_minor_hash = fname->minor_hash;
} else {
if (info->next_hash == ~0) {
- filp->f_pos = EXT4_HTREE_EOF;
+ filp->f_pos = ext4_get_htree_eof(filp);
break;
}
info->curr_hash = info->next_hash;
@@ -540,3 +652,15 @@
return 0;
}
+
+const struct file_operations ext4_dir_operations = {
+ .llseek = ext4_dir_llseek,
+ .read = generic_read_dir,
+ .readdir = ext4_readdir,
+ .unlocked_ioctl = ext4_ioctl,
+#ifdef CONFIG_COMPAT
+ .compat_ioctl = ext4_compat_ioctl,
+#endif
+ .fsync = ext4_sync_file,
+ .release = ext4_release_dir,
+};
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 513004f..8b64a00 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1612,7 +1612,11 @@
u32 *seed;
};
-#define EXT4_HTREE_EOF 0x7fffffff
+
+/* 32 and 64 bit signed EOF for dx directories */
+#define EXT4_HTREE_EOF_32BIT ((1UL << (32 - 1)) - 1)
+#define EXT4_HTREE_EOF_64BIT ((1ULL << (64 - 1)) - 1)
+
/*
* Control parameters used by ext4_htree_next_block
diff --git a/fs/ext4/hash.c b/fs/ext4/hash.c
index ac8f168..fa8e491 100644
--- a/fs/ext4/hash.c
+++ b/fs/ext4/hash.c
@@ -200,8 +200,8 @@
return -1;
}
hash = hash & ~1;
- if (hash == (EXT4_HTREE_EOF << 1))
- hash = (EXT4_HTREE_EOF-1) << 1;
+ if (hash == (EXT4_HTREE_EOF_32BIT << 1))
+ hash = (EXT4_HTREE_EOF_32BIT - 1) << 1;
hinfo->hash = hash;
hinfo->minor_hash = minor_hash;
return 0;