This adds a new ioctl, EXT4_IOC_32BITHASH, which allows a
userspace application to request 32-bit rather than 64-bit
hashes from readdir on an indexed / dx / htree directory.
Gluster had been relying on the top bits of the d_off being
free; there are some reports that filling all 64 bits breaks
Samba as well. The infrastructure to return 32-bit hashes
already exists; NFS can turn it on, and it's turned on for
32-bit processes as well. So it's just a matter of flipping
on the f_mode flag before readdir starts.
Care needs to be taken that we don't change the FMODE flag
after readdir has been started, so we make sure that
filp->private_data has not yet been set before we set the flag.
(Thanks Zach!).
Pre-submission-fixes-by: Zach Brown <zab@xxxxxxxxxx>
Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
---
V2:
fix "readir" typo
rename goto target to *_out like others
remove parameter; we can't really ever turn this back off once it's used.
closing and reopening is the only way to get back to 64 bit hashes.
diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c
index d8cd1f0..5e3a316 100644
--- a/fs/ext4/dir.c
+++ b/fs/ext4/dir.c
@@ -39,7 +39,7 @@ static int ext4_dx_readdir(struct file *filp,
*
* Return 1 if it is a dx dir, 0 if not
*/
-static int is_dx_dir(struct inode *inode)
+int is_dx_dir(struct inode *inode)
{
struct super_block *sb = inode->i_sb;
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 3b83cd6..44a9b52 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -614,6 +614,7 @@ enum {
/* note ioctl 10 reserved for an early version of the FIEMAP ioctl */
/* note ioctl 11 reserved for filesystem-independent FIEMAP ioctl */
#define EXT4_IOC_ALLOC_DA_BLKS _IO('f', 12)
+#define EXT4_IOC_32BITHASH _IO('f', 13)
#define EXT4_IOC_MOVE_EXT _IOWR('f', 15, struct move_extent)
#define EXT4_IOC_RESIZE_FS _IOW('f', 16, __u64)
@@ -1953,6 +1954,7 @@ extern unsigned ext4_num_overhead_clusters(struct super_block *sb,
ext4_fsblk_t ext4_inode_to_goal_block(struct inode *);
/* dir.c */
+extern int is_dx_dir(struct inode *inode);
extern int __ext4_check_dir_entry(const char *, unsigned int, struct inode *,
struct file *,
struct ext4_dir_entry_2 *,
diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index 721f4d3..1d1f7f1 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -356,7 +356,34 @@ group_add_out:
mnt_drop_write_file(filp);
return err;
}
+ case EXT4_IOC_32BITHASH: {
+ int err = 0;
+ /* Serialize with readdir */
+ if ((err = mutex_lock_killable(&inode->i_mutex)))
+ return err;
+
+ /* protect f_mode */
+ spin_lock(&filp->f_lock);
+
+ /* Only valid for htree directories */
+ if (!S_ISDIR(inode->i_mode) || !is_dx_dir(inode)) {
+ err = -EINVAL;
+ goto hash32bits_out;
+ }
+
+ /* Have we already started readdir on this dx dir? */
+ if (filp->private_data) {
+ err = -EINVAL;
+ goto hash32bits_out;
+ }
+
+ filp->f_mode |= FMODE_32BITHASH;
+hash32bits_out:
+ spin_unlock(&filp->f_lock);
+ mutex_unlock(&inode->i_mutex);
+ return err;
+ }
case EXT4_IOC_RESIZE_FS: {
ext4_fsblk_t n_blocks_count;
struct super_block *sb = inode->i_sb;
--
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