From: "J. Bruce Fields" <bfields@xxxxxxxxxx> > The getacl code is allocating enough space to handle the ACL data but > not to handle the bitmask, which can lead to spurious ERANGE errors when > the end of the ACL gets close to a page boundary. > > Dros addressed this by letting the rpc layer allocate pages as necessary > on demand, as the NFSv3 ACL code does. > > On its own that didn't do the job either, because we don't handle the > case where xdr_shrink_bufhead needs to move data around in the xdr buf. > And xdr_shrink_bufhead was getting called every time due to an incorrect > estimate in an xdr_inline_pages call. > > So, I fixed that estimate. That still leaves the chance of a bug in the > rare case xdr_shrink_bufhead is called. > > We could fix up the handling of the xdr_shrink_bufhead case, but I don't > see the point of shifting this data around in the first place. We're > not doing anything like zero-copy here, we're just going to copy the > data out into the buffer we were passed. The NFSv3 ACL code doesn't > bother with this. > > It's simpler just to pass down the buffer to the xdr layer and let it > copy the ACL out. > > The result looks a lot simpler and more obviously correct than this code > has been, though I'm not particularly happy with the sequence of patches > that gets us there; it would be better to squash together Dros's and my > patch and then split out the result some more sensible way. Done; here it is split out so the first two patches are minimal bugfixes, the next two do some minor cleanup, the fifth converts to copying data into "buf" from the xdr decoder, and the final one converts to on-demand allocation (the part Chuck is asking about). I left Dros as the author on the minimal ERANGE fix and the on-demand allocation, though that choice is a little arbitrary as the changes are all split up differently; Dros, let me know if that's problem. It'd be nice to get at least the first two in (and possibly cc'd to stable as well). --b. > > Sorry for the delay getting back to this. Older discussions: > > https://marc.info/?t=138452791200001&r=1&w=2 > http://marc.info/?t=138506891000003&r=1&w=2 J. Bruce Fields (4): NFSv4: fix getacl head length estimation NFSv4: minor acl caching policy documentation NFSv4: minor getacl cleanup NFSv4: simplify getacl decoding Weston Andros Adamson (2): NFSv4: fix getacl ERANGE for some ACL buffer sizes NFSv4: allow getacl rpc to allocate pages on demand fs/nfs/nfs4proc.c | 114 +++++++++++++++++++++++------------------------- fs/nfs/nfs4xdr.c | 29 +++--------- include/linux/nfs_xdr.h | 4 +- 3 files changed, 62 insertions(+), 85 deletions(-) -- 2.9.3 -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
