On 28 Jul 2016, at 16:03, Benjamin Coddington wrote:
> On 28 Jul 2016, at 14:47, Trond Myklebust wrote:
>
>> On Thu, 2016-07-28 at 14:41 -0400, Benjamin Coddington wrote:
>>> Block/SCSI layout write completion may add committable extents to the
>>> extent tree before updating the layout's last-written byte under the
>>> inode
>>> lock. If a sync happens before this value is updated, then
>>> prepare_layoutcommit may find and encode these extents which would
>>> produce
>>> a LAYOUTCOMMIT request whose encoded extents are larger than the
>>> request's
>>> loca_length.
>>>
>>> Fix this by updating the last_write_offset to match the currently
>>> encoded
>>> extents.
>>>
>>> Signed-off-by: Benjamin Coddington <bcodding@xxxxxxxxxx>
>>> ---
>>> fs/nfs/blocklayout/extent_tree.c | 6 ++++--
>>> 1 file changed, 4 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/fs/nfs/blocklayout/extent_tree.c
>>> b/fs/nfs/blocklayout/extent_tree.c
>>> index 992bcb19c11e..18ae1fd2175e 100644
>>> --- a/fs/nfs/blocklayout/extent_tree.c
>>> +++ b/fs/nfs/blocklayout/extent_tree.c
>>> @@ -518,7 +518,7 @@ static __be32 *encode_scsi_range(struct
>>> pnfs_block_extent *be, __be32 *p)
>>> }
>>>
>>> static int ext_tree_encode_commit(struct pnfs_block_layout *bl,
>>> __be32 *p,
>>> - size_t buffer_size, size_t *count)
>>> + size_t buffer_size, size_t *count, __u64 *lastbyte)
>>> {
>>> struct pnfs_block_extent *be;
>>> int ret = 0;
>>> @@ -541,6 +541,8 @@ static int ext_tree_encode_commit(struct
>>> pnfs_block_layout *bl, __be32 *p,
>>> else
>>> p = encode_block_extent(be, p);
>>> be->be_tag = EXTENT_COMMITTING;
>>> + if ((ext_f_end(be) << SECTOR_SHIFT) - 1 > *lastbyte)
>>> + *lastbyte = (ext_f_end(be) << SECTOR_SHIFT)
>>> - 1;
>>
>> Won't this cause the file size to be always sector aligned on the
>> server? I was assuming that we would have to store the lastbyte
>> atomically with setting up the commit in ext_tree_mark_written().
>
> You're right. It is incorrect. I'll fix it.
This turns out to be a little trickier than I thought, and so is taking me
longer than I have time at the moment. Due to travel, I'll have to come
back to this week after next. Thanks for catching my stupid mistake.
Ben
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