(ie even if there is a Windows bug on close with delayed updates to
allocation size)
On Fri, Mar 19, 2021 at 1:48 PM Steve French <smfrench@xxxxxxxxx> wrote:
>
> Well ... it is a little complicated to query it on close in the
> current cifs.ko compounding code and allocation size can change on the
> server so returning a 'plausible' allocation size rather than an
> impossible one is progress.
>
> On Fri, Mar 19, 2021 at 1:26 PM Tom Talpey <tom@xxxxxxxxxx> wrote:
> >
> > Hrm. I am still uneasy about making up a number. It could break
> > an application. And the issue isn't even in the client!
> >
> > Did you ping Neal, or contact dochelp about the Windows server
> > behavior? I'd be happy to but I don't have any context, including
> > which filesystem is doing this.
> >
> > On 3/19/2021 2:08 PM, Steve French wrote:
> > > Yes - the Linux terminology is confusing. Quoting from Ubuntu docs
> > > e.g. about stat output
> > >
> > > "IO Block" in stat's output is the preferred number of
> > > bytes that the file system uses for reading and writing files...
> > > "Blocks", on the other hand, counts how many 512-bytes blocks
> > > are allocated on disk for the file.
> > >
> > > So for NFS and SMB3 mounts they return 1MB for "IO Block" size.
> > >
> > > statfs on the other hand shows what the server thinks the block size
> > > is (often 4K) but
> > > that is a different field.
> > >
> > > And of course number of "blocks" in stat output is meant to return
> > > allocation size
> > > (in 512 byte units for historical reasons, even if most file systems
> > > don't use 512
> > > byte blocks anymore)
> > >
> > >
> > > On Fri, Mar 19, 2021 at 12:52 PM Tom Talpey <tom@xxxxxxxxxx> wrote:
> > >>
> > >> But it's not the block size here, it's the cluster size. Block
> > >> size is the per-io hunk, allocation size is the number of blocks
> > >> lined up to receive it.
> > >>
> > >> Perhaps the safest number is the file size itself, unrounded.
> > >>
> > >> On 3/19/2021 1:46 PM, Steve French wrote:
> > >>> e.g. stat reports much larger than 512 byte block size over SMB3
> > >>>
> > >>> # stat /mnt2/foo
> > >>> File: /mnt2/foo
> > >>> Size: 65536 Blocks: 128 IO Block: 1048576 regular file
> > >>> Device: 34h/52d Inode: 88946092640651991 Links: 1
> > >>>
> > >>> and local file systems do the same ie "blocks" is unrelated to block size
> > >>> the fs reports. Here is an example to XFS locally
> > >>>
> > >>> # stat Makefile
> > >>> File: Makefile
> > >>> Size: 66247 Blocks: 136 IO Block: 4096 regular file
> > >>> Device: 10302h/66306d Inode: 1076242180 Links: 1
> > >>>
> > >>> On Fri, Mar 19, 2021 at 12:42 PM Steve French <smfrench@xxxxxxxxx> wrote:
> > >>>>
> > >>>> We report the block size properly (typically much larger) - but the
> > >>>> kernel API returns allocation size in 512 byte units no matter what the
> > >>>> block size is. Number of blocks returned for the kernel API
> > >>>> inode->i_blocks
> > >>>> is unrelated to the block size (simply allocation_size/512 rounded up by 1).
> > >>>>
> > >>>> On Fri, Mar 19, 2021 at 12:38 PM Tom Talpey <tom@xxxxxxxxxx> wrote:
> > >>>>>
> > >>>>> On 3/19/2021 1:25 AM, Steve French wrote:
> > >>>>>> Applications that create and extend and write to a file do not
> > >>>>>> expect to see 0 allocation size. When file is extended,
> > >>>>>> set its allocation size to a plausible value until we have a
> > >>>>>> chance to query the server for it. When the file is cached
> > >>>>>> this will prevent showing an impossible number of allocated
> > >>>>>> blocks (like 0). This fixes e.g. xfstests 614 which does
> > >>>>>>
> > >>>>>> 1) create a file and set its size to 64K
> > >>>>>> 2) mmap write 64K to the file
> > >>>>>> 3) stat -c %b for the file (to query the number of allocated blocks)
> > >>>>>>
> > >>>>>> It was failing because we returned 0 blocks. Even though we would
> > >>>>>> return the correct cached file size, we returned an impossible
> > >>>>>> allocation size.
> > >>>>>>
> > >>>>>> Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
> > >>>>>> CC: <stable@xxxxxxxxxxxxxxx>
> > >>>>>> ---
> > >>>>>> fs/cifs/inode.c | 12 ++++++++++--
> > >>>>>> 1 file changed, 10 insertions(+), 2 deletions(-)
> > >>>>>>
> > >>>>>> diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
> > >>>>>> index 7c61bc9573c0..17a2c87b811c 100644
> > >>>>>> --- a/fs/cifs/inode.c
> > >>>>>> +++ b/fs/cifs/inode.c
> > >>>>>> @@ -2395,7 +2395,7 @@ int cifs_getattr(struct user_namespace
> > >>>>>> *mnt_userns, const struct path *path,
> > >>>>>> * We need to be sure that all dirty pages are written and the server
> > >>>>>> * has actual ctime, mtime and file length.
> > >>>>>> */
> > >>>>>> - if ((request_mask & (STATX_CTIME | STATX_MTIME | STATX_SIZE)) &&
> > >>>>>> + if ((request_mask & (STATX_CTIME | STATX_MTIME | STATX_SIZE |
> > >>>>>> STATX_BLOCKS)) &&
> > >>>>>> !CIFS_CACHE_READ(CIFS_I(inode)) &&
> > >>>>>> inode->i_mapping && inode->i_mapping->nrpages != 0) {
> > >>>>>> rc = filemap_fdatawait(inode->i_mapping);
> > >>>>>> @@ -2585,6 +2585,14 @@ cifs_set_file_size(struct inode *inode, struct
> > >>>>>> iattr *attrs,
> > >>>>>> if (rc == 0) {
> > >>>>>> cifsInode->server_eof = attrs->ia_size;
> > >>>>>> cifs_setsize(inode, attrs->ia_size);
> > >>>>>> + /*
> > >>>>>> + * i_blocks is not related to (i_size / i_blksize),
> > >>>>>> + * but instead 512 byte (2**9) size is required for
> > >>>>>> + * calculating num blocks. Until we can query the
> > >>>>>> + * server for actual allocation size, this is best estimate
> > >>>>>> + * we have for the blocks allocated for this file
> > >>>>>> + */
> > >>>>>> + inode->i_blocks = (512 - 1 + attrs->ia_size) >> 9;
> > >>>>>
> > >>>>> I don't think 512 is a very robust choice, no server uses anything
> > >>>>> so small any more. MS-FSA requires the allocation quantum to be the
> > >>>>> volume cluster size. Is that value available locally?
> > >>>>>
> > >>>>> Tom.
> > >>>>>
> > >>>>>> /*
> > >>>>>> * The man page of truncate says if the size changed,
> > >>>>>> @@ -2912,7 +2920,7 @@ cifs_setattr_nounix(struct dentry *direntry,
> > >>>>>> struct iattr *attrs)
> > >>>>>> sys_utimes in which case we ought to fail the call back to
> > >>>>>> the user when the server rejects the call */
> > >>>>>> if ((rc) && (attrs->ia_valid &
> > >>>>>> - (ATTR_MODE | ATTR_GID | ATTR_UID | ATTR_SIZE)))
> > >>>>>> + (ATTR_MODE | ATTR_GID | ATTR_UID | ATTR_SIZE)))
> > >>>>>> rc = 0;
> > >>>>>> }
> > >>>>>>
> > >>>>
> > >>>>
> > >>>>
> > >>>> --
> > >>>> Thanks,
> > >>>>
> > >>>> Steve
> > >>>
> > >>>
> > >>>
> > >
> > >
> > >
> > > --
> > > Thanks,
> > >
> > > Steve
> > >
>
>
>
> --
> Thanks,
>
> Steve
--
Thanks,
Steve
