| Message ID | CAKcLGm821VWB5agAEeOuzAvf=YMdeG45HJ8RRNP2M-5sfnQvnA@mail.gmail.com (mailing list archive) |
|---|---|
| State | Superseded, archived |
| Headers | show |
On 02/26/2014 05:39 AM, Mitch Harder wrote: > On Mon, Feb 24, 2014 at 7:38 PM, Wang Shilong > <wangsl.fnst@cn.fujitsu.com> wrote: >> Hi Mitch, >> >> >> On 02/25/2014 07:03 AM, Mitch Harder wrote: >>> On Mon, Feb 24, 2014 at 5:55 AM, Wang Shilong >>> <wangsl.fnst@cn.fujitsu.com> wrote: >>>> We found btrfsck will output backrefs mismatch while the filesystem >>>> is defenitely ok. >>>> >>>> The problem is that check_block() don't return right value,which >>>> makes btrfsck won't walk all tree blocks thus we don't get a consistent >>>> filesystem, we will fail to check extent refs etc. >>>> >>>> Reported-by: Gui Hecheng <guihc.fnst@cn.fujitsu.com> >>>> Signed-off-by: Wang Shilong <wangsl.fnst@cn.fujitsu.com> >>>> --- >>>> cmds-check.c | 2 +- >>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>> >>>> diff --git a/cmds-check.c b/cmds-check.c >>>> index a2afae6..253569f 100644 >>>> --- a/cmds-check.c >>>> +++ b/cmds-check.c >>>> @@ -2477,7 +2477,7 @@ static int check_block(struct btrfs_trans_handle >>>> *trans, >>>> struct cache_extent *cache; >>>> struct btrfs_key key; >>>> enum btrfs_tree_block_status status; >>>> - int ret = 1; >>>> + int ret = 0; >>>> int level; >>>> >>>> cache = lookup_cache_extent(extent_cache, buf->start, buf->len); >>>> -- >>> I tried this fix on a broken btrfs volume I've been trying to repair, >>> and it seemed to put me in an infinite loop. >>> >>> I agree that something seems wrong with the way the caller of >>> check_block uses the return value, and I also noticed that it seemed >>> to exit before walking all the tree blocks. >>> >>> But I think the problem is more subtle than flipping the default ret >>> value from 1 to 0. >> No, not really even though i know there are other problems with fsck repair >> mode. >> But this problem should be fixed and pushed into btrfs-progsv3.13.(Notice, >> the below problem did not exist in btrfs-progsv3.12) >> >> An easy way to trigger this problem: >> >> # mkfs.btrfs -f /dev/sda9 >> # mount /dev/sda9 /mnt >> # dd if=/dev/zero of=/mnt/data bs=4k count=10240 oflag=direct >> # btrfs sub snapshot /mnt /mnt/snap1 >> # btrfs sub snapshot /mnt /mnt/snap2 >> # umount /mnt >> # btrfs check /dev/sda9 >> >> After applying this patch, the above problems did not exist. >> Feel free to correct me if i miss something here.^_^ >> > I took a closer look at the check_block function today, and it looks > to me like the problem is that the return value is not modified when > BTRFS_BLOCK_FLAG_FULL_BACKREF is set. Hm, i'd say no. Let's see what is check_block() doing. It firstly check if there exists next block to deal, if not, return 1 directly. and then we do some checks with that block, and we only explictly set @ret with error when we found an error. So why we got such a regression when josef changed codes, it was because firstly we set @ret with a none-zero value. So we had to take care of error and success case both for the following codes! I was considering your suggestion when i was writting patch, but IMO this patch makes codes less error-prone. I won't change the patch unless i am really missing something here. Thanks, Wang > > @@ -2521,14 +2521,17 @@ static int check_block(struct btrfs_trans_handle *trans, > } > } else { > rec->content_checked = 1; > - if (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF) > + if (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF) { > rec->owner_ref_checked = 1; > + ret = 0; > + } > else { > ret = check_owner_ref(root, rec, buf); > if (!ret) > rec->owner_ref_checked = 1; > } > > For me, in this function I would lean towards an initial return value > that must be updated by having check_block() make an affirmative > PASS/FAIL decision on the block. > > What do you think about something like this? > > diff --git a/cmds-check.c b/cmds-check.c > index ffc5d3e..55070da 100644 > --- a/cmds-check.c > +++ b/cmds-check.c > @@ -2477,7 +2477,7 @@ static int check_block(struct btrfs_trans_handle *trans, > struct cache_extent *cache; > struct btrfs_key key; > enum btrfs_tree_block_status status; > - int ret = 1; > + int ret = -EINVAL; > int level; > > cache = lookup_cache_extent(extent_cache, buf->start, buf->len); > @@ -2521,14 +2521,17 @@ static int check_block(struct btrfs_trans_handle *trans, > } > } else { > rec->content_checked = 1; > - if (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF) > + if (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF) { > rec->owner_ref_checked = 1; > + ret = 0; > + } > else { > ret = check_owner_ref(root, rec, buf); > if (!ret) > rec->owner_ref_checked = 1; > } > } > + BUG_ON(ret == -EINVAL); > if (!ret) > maybe_free_extent_rec(extent_cache, rec); > return ret; > -- > -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/cmds-check.c b/cmds-check.c index ffc5d3e..55070da 100644 --- a/cmds-check.c +++ b/cmds-check.c @@ -2477,7 +2477,7 @@ static int check_block(struct btrfs_trans_handle *trans, struct cache_extent *cache; struct btrfs_key key; enum btrfs_tree_block_status status; - int ret = 1; + int ret = -EINVAL; int level; cache = lookup_cache_extent(extent_cache, buf->start, buf->len); @@ -2521,14 +2521,17 @@ static int check_block(struct btrfs_trans_handle *trans, } } else { rec->content_checked = 1; - if (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF) + if (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF) { rec->owner_ref_checked = 1; + ret = 0; + } else { ret = check_owner_ref(root, rec, buf); if (!ret) rec->owner_ref_checked = 1; } } + BUG_ON(ret == -EINVAL); if (!ret) maybe_free_extent_rec(extent_cache, rec); return ret;