On Thu, 16 Aug 2012, Miklos Szeredi wrote:
> Miklos Szeredi <miklos@xxxxxxxxxx> writes:
>
> > Sage Weil <sage@xxxxxxxxxxx> writes:
> >
> >> Hi Miklos,
> >>
> >> I found some time to track down the O_CREAT error code issue. Patch is
> >> below. Does this look correct?
> >>
> >> I was reproducing with
> >>
> >> ceph-fuse mnt
> >> mkdir -p mnt/a
> >> cd mnt
> >> .../pjd-fstest-20080816/fstest -u 65534 -g 65534 open a/foo O_RDONLY,O_CREAT 0644
> >>
> >> EACCES is expected, ENOENT was returned instead.
> >
> > I don't quite undersdand what is happending here.
> >
> > Why does ceph-fuse return ENOENT here? Returning ENOENT for O_CREAT
> > only makes sense if the parent directory doesn't exist, but that's not
> > the case here.
>
> More specifically, the initial lookup will return ENOENT, that's fine.
>
> But in that case fuse_atomic_open() will do a FUSE_CREATE for which
> ENOENT is not the right answer.
I didn't dig deeply into what fuse_lookup() itself was doing, but the
short version is:
- namei.c's atomic_open() gets -EACCES from the may_o_create() check, sets
create_error, and clears O_CREAT from the flags
- fuse_atomic_open() calls fuse_lookup(), which returns NULL and leaves
entry->d_inode == NULL. ceph-fuse's lookup method returned -ENOENT.
fuse_lookup() is just hashing the negative dentry instead of returning
ENOENT.
- fuse_atomic_open() sees O_CREAT is not set and calls finish_no_open().
- the existing ENOENT -> EACCES check in atomic_open() (below) fails
because fuse_atomic_open() returned 1:
if (error < 0) {
if (create_error && error == -ENOENT)
error = create_error;
goto out;
}
This patch just applies the same ENOENT->EACCES logic to the equivalent
negative/null dentry case.
> Can you post the relevant part from the filesytem's debug log?
The relevant bit is
unique: 11, opcode: GETATTR (3), nodeid: 1, insize: 56, pid: 8502
unique: 11, success, outsize: 120
unique: 12, opcode: LOOKUP (1), nodeid: 1, insize: 42, pid: 8502
unique: 12, success, outsize: 144
unique: 13, opcode: GETATTR (3), nodeid: 1099511627776, insize: 56, pid: 8502
unique: 13, success, outsize: 120
unique: 14, opcode: GETATTR (3), nodeid: 1099511627776, insize: 56, pid: 8502
unique: 14, success, outsize: 120
unique: 15, opcode: LOOKUP (1), nodeid: 1099511627776, insize: 45, pid: 8502
unique: 15, error: -2 (No such file or directory), outsize: 16
Thanks-
sage
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