On 03/05/2013 02:26 AM, Gregory Farnum wrote:
> On Thu, Feb 28, 2013 at 10:46 PM, Yan, Zheng <zheng.z.yan@xxxxxxxxx> wrote:
>> From: "Yan, Zheng" <zheng.z.yan@xxxxxxxxx>
>>
>> ceph_aio_write() has an optimization that marks CEPH_CAP_FILE_WR
>> cap dirty before data is copied to page cache and inode size is
>> updated. The optimization avoids slow cap revocation caused by
>> balance_dirty_pages(), but introduces inode size update race. If
>> ceph_check_caps() flushes the dirty cap before the inode size is
>> updated, MDS can miss the new inode size. So just remove the
>> optimization.
>>
>> Signed-off-by: Yan, Zheng <zheng.z.yan@xxxxxxxxx>
>> ---
>> fs/ceph/file.c | 42 +++++++++++++++++-------------------------
>> 1 file changed, 17 insertions(+), 25 deletions(-)
>>
>> diff --git a/fs/ceph/file.c b/fs/ceph/file.c
>> index a949805..28ef273 100644
>> --- a/fs/ceph/file.c
>> +++ b/fs/ceph/file.c
>> @@ -724,9 +724,12 @@ static ssize_t ceph_aio_write(struct kiocb *iocb, const struct iovec *iov,
>> if (ceph_snap(inode) != CEPH_NOSNAP)
>> return -EROFS;
>>
>> + sb_start_write(inode->i_sb);
>> retry_snap:
>> - if (ceph_osdmap_flag(osdc->osdmap, CEPH_OSDMAP_FULL))
>> - return -ENOSPC;
>> + if (ceph_osdmap_flag(osdc->osdmap, CEPH_OSDMAP_FULL)) {
>> + ret = -ENOSPC;
>> + goto out;
>> + }
>> __ceph_do_pending_vmtruncate(inode);
>> dout("aio_write %p %llx.%llx %llu~%u getting caps. i_size %llu\n",
>> inode, ceph_vinop(inode), pos, (unsigned)iov->iov_len,
>> @@ -750,29 +753,10 @@ retry_snap:
>> ret = ceph_sync_write(file, iov->iov_base, iov->iov_len,
>> &iocb->ki_pos);
>> } else {
>> - /*
>> - * buffered write; drop Fw early to avoid slow
>> - * revocation if we get stuck on balance_dirty_pages
>> - */
>> - int dirty;
>> -
>> - spin_lock(&ci->i_ceph_lock);
>> - dirty = __ceph_mark_dirty_caps(ci, CEPH_CAP_FILE_WR);
>> - spin_unlock(&ci->i_ceph_lock);
>> - ceph_put_cap_refs(ci, got);
>> -
>> - ret = generic_file_aio_write(iocb, iov, nr_segs, pos);
>> - if ((ret >= 0 || ret == -EIOCBQUEUED) &&
>> - ((file->f_flags & O_SYNC) || IS_SYNC(file->f_mapping->host)
>> - || ceph_osdmap_flag(osdc->osdmap, CEPH_OSDMAP_NEARFULL))) {
>> - err = vfs_fsync_range(file, pos, pos + ret - 1, 1);
>> - if (err < 0)
>> - ret = err;
>> - }
>> -
>> - if (dirty)
>> - __mark_inode_dirty(inode, dirty);
>> - goto out;
>> + mutex_lock(&inode->i_mutex);
>> + ret = __generic_file_aio_write(iocb, iov, nr_segs,
>> + &iocb->ki_pos);
>> + mutex_unlock(&inode->i_mutex);
>
> Hmm, you're here passing in a different value than the removed
> generic_file_aio_write() call did — &iocb->ki_pos instead of pos.
> Everything else is using the pos parameter so I rather expect that
> should still be used here?
They always have the same value, see the BUG_ON in generic_file_aio_write()
> Also a quick skim of the interfaces makes me think that the two
> versions aren't interchangeable — __generic_file_aio_write() also
> handles O_SYNC in addition to grabbing i_mutex. Why'd you switch them?
ceph has its own code that handles O_SYNC case. I want to make sb_start_write()
covers ceph_sync_write(), that's the reason I use __generic_file_aio_write() here.
Regards
Yan, Zheng
> (I haven't checked deep enough to see if the unlocked version is
> correct or not, but it does say that's what most filesystems should
> use.)
> -Greg
>
>
>> }
>>
>> if (ret >= 0) {
>> @@ -790,12 +774,20 @@ out_put:
>> ceph_cap_string(got));
>> ceph_put_cap_refs(ci, got);
>>
>> + if (ret >= 0 &&
>> + ((file->f_flags & O_SYNC) || IS_SYNC(file->f_mapping->host) ||
>> + ceph_osdmap_flag(osdc->osdmap, CEPH_OSDMAP_NEARFULL))) {
>> + err = vfs_fsync_range(file, pos, pos + ret - 1, 1);
>> + if (err < 0)
>> + ret = err;
>> + }
>> out:
>> if (ret == -EOLDSNAPC) {
>> dout("aio_write %p %llx.%llx %llu~%u got EOLDSNAPC, retrying\n",
>> inode, ceph_vinop(inode), pos, (unsigned)iov->iov_len);
>> goto retry_snap;
>> }
>> + sb_end_write(inode->i_sb);
>>
>> return ret;
>> }
>> --
>> 1.7.11.7
>>
>> --
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