Can't remove SA xattr when xattr=on #3472
Comments
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I noticed this when we added xattr=sa to OSX. It has some other situations as well (if I remember correctly, having the same xattr in both SA and "on" could lead to doubles when listing). It felt like xattr=sa should be a creation-time setting, and going from xattr=sa to xattr=on is not supported. But since you bring it up here, perhaps that wasn't intentional.. ? |
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I believe the intention is/was to support switching back and forth. There are situations where it will fall back to a directory-based xattr anyways. If the total size for all xattrs on a file gets too big (I think more than half the maximum block size?). |
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I've got a patch in one of my branches that starts trying to make it work more sensibly. I'll try to dig it up. EDIT: Removed email quoting. |
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The patch I was working on is at https://github.com/dweeezil/zfs/tree/xattr-sa. One of the first issues I was trying to address is the apparent duplicates seen when iterating the xattrs and when the same xattr exists as an SA xattr and a dir-style xattr. |
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@dweeezil Have you tried that patch in production? |
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0e08566 looked straight forward enough to me so I just went with it. So far it works as advertised. Is there something missing that prevents it from inclusion? |
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@mmehnert I've not exercised the patch very thoroughly and, quite honestly, it's been quite awhile since I wrote it. AFAIK, it ought to be safe and leaving the empty xattr directory laying around should not cause any problems. I think the main reason I didn't post a pull request as-is is because I wanted to make this patch part of a larger rationalization of sa-versus-dir xattrs, possibly including additional values of the xattr property to provide for more fine-grained control over the manner in which transitions between xattr=on and xattr=sa are handled. At this point, I suspect you've given it more of a workout than I ever did :) |
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@dweeezil |
When replacing an xattr would cause overflowing in SA, we would fallback
to xattr dir. However, current implementation don't clear the one in SA,
so we would end up with duplicated SA.
For example, running the following script on an xattr=sa filesystem
would cause duplicated "user.1".
-- dup_xattr.sh begin --
randbase64()
{
dd if=/dev/urandom bs=1 count=$1 2>/dev/null | openssl enc -a -A
}
file=$1
touch $file
setfattr -h -n user.1 -v `randbase64 5000` $file
setfattr -h -n user.2 -v `randbase64 20000` $file
setfattr -h -n user.3 -v `randbase64 20000` $file
setfattr -h -n user.1 -v `randbase64 20000` $file
getfattr -m. -d $file
-- dup_xattr.sh end --
Also, when a filesystem is switch from xattr=sa to xattr=on, it will
never modify those in SA. This would cause strange behavior like, you
cannot delete an xattr, or setxattr would cause duplicate and the result
would not match when you getxattr.
For example, the following shell sequence.
-- shell begin --
$ sudo zfs set xattr=sa pp/fs0
$ touch zzz
$ setfattr -n user.test -v asdf zzz
$ sudo zfs set xattr=on pp/fs0
$ setfattr -x user.test zzz
setfattr: zzz: No such attribute
$ getfattr -d zzz
user.test="asdf"
$ setfattr -n user.test -v zxcv zzz
$ getfattr -d zzz
user.test="asdf"
user.test="asdf"
-- shell end --
We fix this behavior, by first finding where the xattr resides before
setxattr. Then, after we successfully updated the xattr in one location,
we will clear the other location. Note that, because update and clear
are not in single tx, we could still end up with duplicated xattr. But
by doing setxattr again, it can be fixed.
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Closes openzfs#3472
Closes openzfs#4153
When replacing an xattr would cause overflowing in SA, we would fallback
to xattr dir. However, current implementation don't clear the one in SA,
so we would end up with duplicated SA.
For example, running the following script on an xattr=sa filesystem
would cause duplicated "user.1".
-- dup_xattr.sh begin --
randbase64()
{
dd if=/dev/urandom bs=1 count=$1 2>/dev/null | openssl enc -a -A
}
file=$1
touch $file
setfattr -h -n user.1 -v `randbase64 5000` $file
setfattr -h -n user.2 -v `randbase64 20000` $file
setfattr -h -n user.3 -v `randbase64 20000` $file
setfattr -h -n user.1 -v `randbase64 20000` $file
getfattr -m. -d $file
-- dup_xattr.sh end --
Also, when a filesystem is switch from xattr=sa to xattr=on, it will
never modify those in SA. This would cause strange behavior like, you
cannot delete an xattr, or setxattr would cause duplicate and the result
would not match when you getxattr.
For example, the following shell sequence.
-- shell begin --
$ sudo zfs set xattr=sa pp/fs0
$ touch zzz
$ setfattr -n user.test -v asdf zzz
$ sudo zfs set xattr=on pp/fs0
$ setfattr -x user.test zzz
setfattr: zzz: No such attribute
$ getfattr -d zzz
user.test="asdf"
$ setfattr -n user.test -v zxcv zzz
$ getfattr -d zzz
user.test="asdf"
user.test="asdf"
-- shell end --
We fix this behavior, by first finding where the xattr resides before
setxattr. Then, after we successfully updated the xattr in one location,
we will clear the other location. Note that, because update and clear
are not in single tx, we could still end up with duplicated xattr. But
by doing setxattr again, it can be fixed.
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Closes #3472
Closes #4153
When replacing an xattr would cause overflowing in SA, we would fallback
to xattr dir. However, current implementation don't clear the one in SA,
so we would end up with duplicated SA.
For example, running the following script on an xattr=sa filesystem
would cause duplicated "user.1".
-- dup_xattr.sh begin --
randbase64()
{
dd if=/dev/urandom bs=1 count=$1 2>/dev/null | openssl enc -a -A
}
file=$1
touch $file
setfattr -h -n user.1 -v `randbase64 5000` $file
setfattr -h -n user.2 -v `randbase64 20000` $file
setfattr -h -n user.3 -v `randbase64 20000` $file
setfattr -h -n user.1 -v `randbase64 20000` $file
getfattr -m. -d $file
-- dup_xattr.sh end --
Also, when a filesystem is switch from xattr=sa to xattr=on, it will
never modify those in SA. This would cause strange behavior like, you
cannot delete an xattr, or setxattr would cause duplicate and the result
would not match when you getxattr.
For example, the following shell sequence.
-- shell begin --
$ sudo zfs set xattr=sa pp/fs0
$ touch zzz
$ setfattr -n user.test -v asdf zzz
$ sudo zfs set xattr=on pp/fs0
$ setfattr -x user.test zzz
setfattr: zzz: No such attribute
$ getfattr -d zzz
user.test="asdf"
$ setfattr -n user.test -v zxcv zzz
$ getfattr -d zzz
user.test="asdf"
user.test="asdf"
-- shell end --
We fix this behavior, by first finding where the xattr resides before
setxattr. Then, after we successfully updated the xattr in one location,
we will clear the other location. Note that, because update and clear
are not in single tx, we could still end up with duplicated xattr. But
by doing setxattr again, it can be fixed.
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Closes openzfs#3472
Closes openzfs#4153
If a file has an SA-based xattr but the dataset has
xattr=onset, the SA-based xattr cannot be removed.The text was updated successfully, but these errors were encountered: