From: Fan Yong <yong.fan@xxxxxxxxxxxxx>
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.
Signed-off-by: Fan Yong <yong.fan@xxxxxxxxxxxxx>
Signed-off-by: Andreas Dilger <adilger@xxxxxxxxxxxxx>
Signed-off-by: Bernd Schubert <bernd.schubert@xxxxxxxxxxxxxxxxxx>
---
fs/ext4/dir.c | 160 ++++++++++++++++++++++++++++++++++---------
fs/fcntl.c | 5 +
include/asm-generic/fcntl.h | 9 ++
3 files changed, 138 insertions(+), 36 deletions(-)
diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c
index 164c560..8258240 100644
--- a/fs/ext4/dir.c
+++ b/fs/ext4/dir.c
@@ -32,24 +32,8 @@ static unsigned char ext4_filetype_table[] = {
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)
{
@@ -254,22 +238,117 @@ out:
return ret;
}
+static inline int is_32bit_api(void)
+{
+#ifdef HAVE_IS_COMPAT_TASK
+ return is_compat_task();
+#else
+ return (BITS_PER_LONG == 32);
+#endif
+}
+
/*
* These functions convert from the major/minor hash to an f_pos
* value.
*
- * 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 should specify O_32BITHASH or O_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 O_32BITHASH nor O_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_flags & O_32BITHASH) ||
+ (!(filp->f_flags & O_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_flags & O_32BITHASH) ||
+ (!(filp->f_flags & O_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_flags & O_32BITHASH) ||
+ (!(filp->f_flags & O_64BITHASH) && is_32bit_api()))
+ return 0;
+ else
+ return pos & 0xffffffff;
+}
+
+/*
+ * 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 is_dx_dir = ext4_test_inode_flag(inode, EXT4_INODE_INDEX);
+
+ mutex_lock(&inode->i_mutex);
+
+ switch (origin) {
+ case SEEK_END:
+ if (unlikely(offset > 0))
+ goto out_err; /* not supported for directories */
+ if (is_dx_dir)
+ offset = EXT4_HTREE_EOF;
+ 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;
+ }
+
+ /* NOTE: relative offsets with dx directories might not work
+ * as expected, as it is difficult to figure out the
+ * correct offset between dx hashes */
+ offset += file->f_pos;
+ break;
+ }
+
+ if (unlikely(offset < 0))
+ goto out_err;
+
+ if (!is_dx_dir) {
+ if (offset > inode->i_sb->s_maxbytes)
+ goto out_err;
+ } else if (offset > EXT4_HTREE_EOF)
+ 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 +409,16 @@ static void free_rb_tree_fname(struct rb_root *root)
}
-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 +509,7 @@ static int call_filldir(struct file *filp, void *dirent,
"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,
@@ -454,7 +534,7 @@ static int ext4_dx_readdir(struct file *filp,
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;
@@ -468,8 +548,8 @@ static int ext4_dx_readdir(struct file *filp,
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);
}
/*
@@ -540,3 +620,15 @@ static int ext4_release_dir(struct inode *inode, struct file *filp)
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/fcntl.c b/fs/fcntl.c
index 22764c7..cb6ef40 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -835,14 +835,15 @@ static int __init fcntl_init(void)
* Exceptions: O_NONBLOCK is a two bit define on parisc; O_NDELAY
* is defined as O_NONBLOCK on some platforms and not on others.
*/
- BUILD_BUG_ON(19 - 1 /* for O_RDONLY being 0 */ != HWEIGHT32(
+ BUILD_BUG_ON(21 - 1 /* for O_RDONLY being 0 */ != HWEIGHT32(
O_RDONLY | O_WRONLY | O_RDWR |
O_CREAT | O_EXCL | O_NOCTTY |
O_TRUNC | O_APPEND | /* O_NONBLOCK | */
__O_SYNC | O_DSYNC | FASYNC |
O_DIRECT | O_LARGEFILE | O_DIRECTORY |
O_NOFOLLOW | O_NOATIME | O_CLOEXEC |
- __FMODE_EXEC | O_PATH
+ __FMODE_EXEC | O_PATH | O_32BITHASH |
+ O_64BITHASH
));
fasync_cache = kmem_cache_create("fasync_cache",
diff --git a/include/asm-generic/fcntl.h b/include/asm-generic/fcntl.h
index 84793c7..a40e1d5 100644
--- a/include/asm-generic/fcntl.h
+++ b/include/asm-generic/fcntl.h
@@ -84,10 +84,19 @@
#define O_PATH 010000000
#endif
+
#ifndef O_NDELAY
#define O_NDELAY O_NONBLOCK
#endif
+#ifndef O_32BITHASH
+#define O_32BITHASH 020000000 /* use 64 bit hash from dir llseek() */
+#endif
+#ifndef O_64BITHASH
+#define O_64BITHASH 040000000 /* use 32 bit hash from dir llseek() */
+#endif
+
+
#define F_DUPFD 0 /* dup */
#define F_GETFD 1 /* get close_on_exec */
#define F_SETFD 2 /* set/clear close_on_exec */
--
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