Messages in this thread | | | Subject | Re: xattr hash error in 4.13-rc with overlayfs over ext4 | From | "zhangyi (F)" <> | Date | Sun, 6 Aug 2017 20:47:20 +0800 |
| |
On 2017/8/3 19:10, Miklos Szeredi Wrote: > On Tue, Aug 1, 2017 at 12:34 PM, Amir Goldstein <amir73il@gmail.com> wrote: >> On Mon, Jul 31, 2017 at 7:08 PM, Miklos Szeredi <miklos@szeredi.hu> wrote: >>> On Thu, Jul 27, 2017 at 10:54 PM, Tahsin Erdogan <tahsin@google.com> wrote: >>>> Still no luck reproducing the error. I am using the test script below >>>> at v4.13-rc2. Do you mind checking my script to see what I am missing? >>> >>> Don't know. I can reliably reproduce it under UML, but not with a >>> VM. What the hell is going on? >>> >> >> Is it the same ext4 image for UML and VM? same image size? same mkfs version? > > Exact same starting image. Same userspace. Same EXT4 kernel config options. > > Thanks, > Miklos >
Hi: I think the root cause of this problem is the hash value not updated when we overwrite the same xattr, please see ext4_xattr_set_entry():
static int ext4_xattr_set_entry(struct ext4_xattr_info *i, struct ext4_xattr_search *s, handle_t *handle, struct inode *inode, bool is_block) { ... if (new_size && new_size == old_size) { size_t offs = le16_to_cpu(here->e_value_offs); void *val = s->base + offs;
here->e_value_size = cpu_to_le32(i->value_len); if (i->value == EXT4_ZERO_XATTR_VALUE) { memset(val, 0, new_size); } else { memcpy(val, i->value, i->value_len); /* Clear padding bytes. */ memset(val + i->value_len, 0, new_size - i->value_len); }
/* Forget updating *here->e_hash* and *s->base->h_hash* here. */
return 0; } ... /* Call ext4_xattr_hash_entry && ext4_xattr_rehash first set */ ... }
Thanks, ZhangYi
| |