Better error message when trying to write EAs too big for file system

[ericzolf]

Hi,

we've got a bug reported which actually didn't have anything to do with a file system full, but most probably to too big EAs on ext4 (according to man 5 xattr it has a limit of 1, 2 or 4KB):

touch xxx
python3
>>> x = '0123456789' * 1024  # 10KB size
>>> import xattr
>>> xattr.setxattr('xxx', 'user.comment', x)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
OSError: [Errno 28] No space left on device

The error message should be more helpful, something like "extended attribute too big for file system limit".

[iustin]

Hmm, interesting. Note that this is the error message coming from the operating system, I'm not processing it in any way.

The man page for the setxattr function mentions both ENOSPC: There is insufficient space remaining to store the extended attribute., and ERANGE: The size of name or value exceeds a filesystem-specific limit.. I would expect the latter (ERANGE) to be returned here, not ENOSPC. I wonder if this can be improved in the ext4 driver?

I did not think about failure modes here, I'll follow-up to see how this fails with various file systems.

[joachimmetz]

FYI per https://ext4.wiki.kernel.org/index.php/Ext4_Disk_Layout#Extended_Attributes

If the disk block fills up, the filesystem returns -ENOSPC.

So ENOSPC corresponds with the documentation

[ericzolf]

That makes it indeed difficult to address properly. Sad, but I wouldn't mind if you chose the issue.

[iustin]

Will close indeed since the problem is upstream.