On 09/06/2013 08:46 AM, majianpeng wrote:
>> Hi,
>>
>> Thank you for the patch.
>>
>> On 09/03/2013 04:52 PM, majianpeng wrote:
>>> For writev/pwritev sync-operatoin, ceph only do the first iov.
>>> It don't think other iovs.Now implement this.
>>> I divided the write-sync-operation into two functions.One for
>>> direct-write,other for none-direct-sync-write.This is because for
>>> none-direct-sync-write we can merge iovs to one.But for direct-write,
>>> we can't merge iovs.
>>>
>>> Signed-off-by: Jianpeng Ma <majianpeng@xxxxxxxxx>
>>> ---
>>> fs/ceph/file.c | 328 +++++++++++++++++++++++++++++++++++++++++++--------------
>>> 1 file changed, 248 insertions(+), 80 deletions(-)
>>>
>>> diff --git a/fs/ceph/file.c b/fs/ceph/file.c
>>> index 7d6a3ee..42c97b3 100644
>>> --- a/fs/ceph/file.c
>>> +++ b/fs/ceph/file.c
>>> @@ -533,17 +533,19 @@ static void ceph_sync_write_unsafe(struct ceph_osd_request *req, bool unsafe)
>>> }
>>> }
>>>
>>> +
>>> /*
>>> - * Synchronous write, straight from __user pointer or user pages (if
>>> - * O_DIRECT).
>>> + * Synchronous write, straight from __user pointer or user pages.
>>> *
>>> * If write spans object boundary, just do multiple writes. (For a
>>> * correct atomic write, we should e.g. take write locks on all
>>> * objects, rollback on failure, etc.)
>>> */
>>> -static ssize_t ceph_sync_write(struct file *file, const char __user *data,
>>> - size_t left, loff_t pos, loff_t *ppos)
>>> +static ssize_t
>>> +ceph_sync_direct_write(struct kiocb *iocb, const struct iovec *iov,
>>> + unsigned long nr_segs, size_t count)
>>> {
>>> + struct file *file = iocb->ki_filp;
>>> struct inode *inode = file_inode(file);
>>> struct ceph_inode_info *ci = ceph_inode(inode);
>>> struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
>>> @@ -557,59 +559,55 @@ static ssize_t ceph_sync_write(struct file *file, const char __user *data,
>>> int written = 0;
>>> int flags;
>>> int check_caps = 0;
>>> - int page_align, io_align;
>>> - unsigned long buf_align;
>>> - int ret;
>>> + int page_align;
>>> + int ret, i;
>>> struct timespec mtime = CURRENT_TIME;
>>> - bool own_pages = false;
>>> + loff_t pos = iocb->ki_pos;
>>>
>>> if (ceph_snap(file_inode(file)) != CEPH_NOSNAP)
>>> return -EROFS;
>>>
>>> - dout("sync_write on file %p %lld~%u %s\n", file, pos,
>>> - (unsigned)left, (file->f_flags & O_DIRECT) ? "O_DIRECT" : "");
>>> + dout("sync_direct_write on file %p %lld~%u\n", file, pos,
>>> + (unsigned)count);
>>>
>>> - ret = filemap_write_and_wait_range(inode->i_mapping, pos, pos + left);
>>> + ret = filemap_write_and_wait_range(inode->i_mapping, pos, pos + count);
>>> if (ret < 0)
>>> return ret;
>>>
>>> ret = invalidate_inode_pages2_range(inode->i_mapping,
>>> pos >> PAGE_CACHE_SHIFT,
>>> - (pos + left) >> PAGE_CACHE_SHIFT);
>>> + (pos + count) >> PAGE_CACHE_SHIFT);
>>> if (ret < 0)
>>> dout("invalidate_inode_pages2_range returned %d\n", ret);
>>>
>>> flags = CEPH_OSD_FLAG_ORDERSNAP |
>>> CEPH_OSD_FLAG_ONDISK |
>>> CEPH_OSD_FLAG_WRITE;
>>> - if ((file->f_flags & (O_SYNC|O_DIRECT)) == 0)
>>> - flags |= CEPH_OSD_FLAG_ACK;
>>> - else
>>> - num_ops++; /* Also include a 'startsync' command. */
>>> + num_ops++; /* Also include a 'startsync' command. */
>>>
>>> - /*
>>> - * we may need to do multiple writes here if we span an object
>>> - * boundary. this isn't atomic, unfortunately. :(
>>> - */
>>> -more:
>>> - io_align = pos & ~PAGE_MASK;
>>> - buf_align = (unsigned long)data & ~PAGE_MASK;
>>> - len = left;
>>> + for (i = 0; i < nr_segs && count; i++) {
>>
>> POSIX requires that write syscall is atomic. I means we should allocate a single OSD request
>> for all buffer segments that belong to the same object.
>>
> I think we could not.
> For direct write, we use ceph_get_direct_page_vector to get pages.
> Given iov1 and iov2 are in the same object. But we can't make the pages of iov1/2 to join together.
> Because for ceph page_vector,it only record the offset of first page.
>
> Or am i missing something?
> Maybe we can use ceph pagelist but it will copy data.
>
I'm wrong with the direct IO case (ext4 doesn't guarantee atomicity in direct write). But please keep
buffered write atomic.
Regards
Yan, Zheng
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
