On Thu, Jan 31, 2013 at 05:50:55PM +0100, Jan Kara wrote:
> On Thu 31-01-13 13:17:53, Zheng Liu wrote:
> > From: Zheng Liu <wenqing.lz@xxxxxxxxxx>
> >
> > By recording the phycisal block and status, extent status tree is able
> > to track the status of every extents. When we call _map_blocks
> > functions to lookup an extent or create a new written/unwritten/delayed
> > extent, this extent will be inserted into extent status tree.
> >
> > We don't load all extents from disk in alloc_inode() because it costs
> > too much memory, and if a file is opened and closed frequently it will
> > takes too much time to load all extent information. So currently when
> > we create/lookup an extent, this extent will be inserted into extent
> > status tree. Hence, the extent status tree may not comprehensively
> > contain all of the extents found in the file.
> >
> > Signed-off-by: Zheng Liu <wenqing.lz@xxxxxxxxxx>
> > Cc: "Theodore Ts'o" <tytso@xxxxxxx>
> > ---
> > fs/ext4/extents.c | 5 +++-
> > fs/ext4/file.c | 6 +++--
> > fs/ext4/inode.c | 73 ++++++++++++++++++++++++++++++++++++-------------------
> > 3 files changed, 56 insertions(+), 28 deletions(-)
> >
> > diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> > index aa9a6d2..d23a654 100644
> > --- a/fs/ext4/extents.c
> > +++ b/fs/ext4/extents.c
> > @@ -2074,7 +2074,7 @@ static int ext4_fill_fiemap_extents(struct inode *inode,
> > }
> >
> > /* This is possible iff next == next_del == EXT_MAX_BLOCKS */
> > - if (next == next_del) {
> > + if (next == next_del && next_del == EXT_MAX_BLOCKS) {
> This doesn't seem to be related, does it?
ext4_ext_next_allocated_block() will return EXT_MAX_BLOCKS when it
reaches the end of file. ext4_find_delayed_extent() does the same
thing. Before tracking written/unwritten extent it is correct because
next never equals to next_del unless both of them equal to
EXT_MAX_BLOCKS. However, after that next is possible to equal to
next_del when they don't reach the end of file. So we need to make sure
next equals to next_del and both of them equal to EXT_MAX_BLOCKS. In
this condition it indicates that we reach the end of file. Am I miss
something?
>
> > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> > index e09c7cf..f0dda2a 100644
> > --- a/fs/ext4/inode.c
> > +++ b/fs/ext4/inode.c
> > @@ -615,18 +615,27 @@ int ext4_map_blocks(handle_t *handle, struct inode *inode,
> > (flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE))
> > ext4_da_update_reserve_space(inode, retval, 1);
> > }
> > - if (flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE) {
> > + if (flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE)
> > ext4_clear_inode_state(inode, EXT4_STATE_DELALLOC_RESERVED);
> >
> > - if (retval > 0 && map->m_flags & EXT4_MAP_MAPPED) {
> > - int ret;
> > -delayed_mapped:
> > - /* delayed allocation blocks has been allocated */
> > - ret = ext4_es_remove_extent(inode, map->m_lblk,
> > - map->m_len);
> > - if (ret < 0)
> > - retval = ret;
> > - }
> > + if (retval > 0) {
> > + int ret, status;
> > +
> > + if (flags & EXT4_GET_BLOCKS_PRE_IO)
> > + status = EXTENT_STATUS_UNWRITTEN;
> > + else if (flags & EXT4_GET_BLOCKS_CONVERT)
> > + status = EXTENT_STATUS_WRITTEN;
> > + else if (flags & EXT4_GET_BLOCKS_UNINIT_EXT)
> > + status = EXTENT_STATUS_UNWRITTEN;
> > + else if (flags & EXT4_GET_BLOCKS_CREATE)
> > + status = EXTENT_STATUS_WRITTEN;
> > + else
> > + BUG_ON(1);
> > +
> > + ret = ext4_es_insert_extent(inode, map->m_lblk, map->m_len,
> > + map->m_pblk, status);
> > + if (ret < 0)
> > + retval = ret;
> Hum, are you sure the extent status will be correct? Won't it be safer to
> just use whatever we have in 'map'?
Your meaning is that we need to ignore the error when we insert a extent
into the extent status tree, right? But that would causes an
inconsistency between status tree and extent tree. Further,
ext4_es_insert_extent() returns EINVAL or ENOMEM. I believe that
reporting an error is a better choice. What do you think?
Thanks,
- Zheng
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
