On Sep 19 2018, Miklos Szeredi <miklos@xxxxxxxxxx> wrote:
> On Wed, Sep 19, 2018 at 7:03 PM, Nikolaus Rath <Nikolaus@xxxxxxxx> wrote:
>> Hi,
>>
>> Are there any conditions under which a write to the fuse file descriptor
>> may block?
>>
>> It seems to me that this should never be the case - except possibly when
>> sending a FUSE_NOTIFY_INVAL_ENTRY or FUSE_NOTIFY_DELETE request that is
>> related for to an ongoing file system operation. Here would would much
>> appreciate if someone could clarify what operations exactly would cause
>> the write to block.
>
> NOTIFY_INVAL_ENTRY and NOTIFY_DELETE lock the parent directory
> i_mutex. Operations which run under i_mutex of parent are: lookup,
> symlink, mknod, mkdir, unlink, rmdir, rename, link, create, rename2.
> Operations which run under i_mutex of object: setattr, unlink, rmdir,
> rename, setxattr, removexattr, readdir, readdirplus, rename2.
Thanks! Could you also confirm if that's the only situation where a
write might block? In other words, in all other cases I can safely skip
a select/poll/epoll for writability of fuse fd and be guaranteed that
the write will proceed immediately?
Best,
-Nikolaus
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