On Wed, 26 Sep 2012 15:07:14 +0200, Jan Kara <jack@xxxxxxx> wrote:
> On Mon 24-09-12 15:44:13, Dmitry Monakhov wrote:
> > ext4_set_io_unwritten_flag() will increment i_unwritten counter, so
> > once we mark end_io with END_IO_UNWRITTEN we have to revert it back
> ^^ EXT4_IO_END_UNWRITTEN
> > on error path.
> >
> > - add missed error checks to prevent counter leakage
> > - ext4_end_io_nolock() will clear END_IO_UNWRITTEN flag to signal
> ^^ EXT4_IO_END_UNWRITTEN
> > that conversion finished.
> > - add BUGON to free_end_io() to prevent similar leackage in future.
> ^^ BUG_ON ^^ext4_free_io_end() ^^ leakage
>
> > Visiable effect of this bug is that unaligned aio_stress may deadlock
> ^^ Visible
>
> Umm, and won't it be more foolproof it we just decrement i_unwritten in
> ext4_free_io_end() when we see EXT4_IO_END_UNWRITTEN set?
I'd like to consider BUG_ON inside ext4_free_io_end as a sanity check to
force all callers to perform all necessary error checks in known context.
>
> That still leaves the mess with EXT4_STATE_DIO_UNWRITTEN unhandled. But
> that's a separate issue. We seem to clear that flag only in
> ext4_ext_direct_IO() although it could be set even when buffered write
> converts extents. And error cases seem to be buggy as well.
No, each unwritten extent will be added to i_complete_io_list regardless
to it's origin (buffered or DIO), and will be completed via
ext4_end_io_nolock(). So assertion is correct.
>
> Honza
>
> > Signed-off-by: Dmitry Monakhov <dmonakhov@xxxxxxxxxx>
> > ---
> > fs/ext4/extents.c | 21 ++++++++++++++-------
> > fs/ext4/page-io.c | 6 +++++-
> > 2 files changed, 19 insertions(+), 8 deletions(-)
> >
> > diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> > index 6eb6b0c..739c21d 100644
> > --- a/fs/ext4/extents.c
> > +++ b/fs/ext4/extents.c
> > @@ -3660,6 +3660,8 @@ ext4_ext_handle_uninitialized_extents(handle_t *handle, struct inode *inode,
> > if ((flags & EXT4_GET_BLOCKS_PRE_IO)) {
> > ret = ext4_split_unwritten_extents(handle, inode, map,
> > path, flags);
> > + if (ret <= 0)
> > + goto out;
> > /*
> > * Flag the inode(non aio case) or end_io struct (aio case)
> > * that this IO needs to conversion to written when IO is
> > @@ -3905,6 +3907,7 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
> > struct ext4_allocation_request ar;
> > ext4_io_end_t *io = (ext4_io_end_t*) EXT4_CUR_AIO_DIO(inode);
> > ext4_lblk_t cluster_offset;
> > + int set_unwritten = 0;
> >
> > ext_debug("blocks %u/%u requested for inode %lu\n",
> > map->m_lblk, map->m_len, inode->i_ino);
> > @@ -4127,13 +4130,8 @@ got_allocated_blocks:
> > * For non asycn direct IO case, flag the inode state
> > * that we need to perform conversion when IO is done.
> > */
> > - if ((flags & EXT4_GET_BLOCKS_PRE_IO)) {
> > - if (io)
> > - ext4_set_io_unwritten_flag(inode, io);
> > - else
> > - ext4_set_inode_state(inode,
> > - EXT4_STATE_DIO_UNWRITTEN);
> > - }
> > + if ((flags & EXT4_GET_BLOCKS_PRE_IO))
> > + set_unwritten = 1;
> > if (ext4_should_dioread_nolock(inode))
> > map->m_flags |= EXT4_MAP_UNINIT;
> > }
> > @@ -4145,6 +4143,15 @@ got_allocated_blocks:
> > if (!err)
> > err = ext4_ext_insert_extent(handle, inode, path,
> > &newex, flags);
> > +
> > + if (!err && set_unwritten) {
> > + if (io)
> > + ext4_set_io_unwritten_flag(inode, io);
> > + else
> > + ext4_set_inode_state(inode,
> > + EXT4_STATE_DIO_UNWRITTEN);
> > + }
> > +
> > if (err && free_on_err) {
> > int fb_flags = flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE ?
> > EXT4_FREE_BLOCKS_NO_QUOT_UPDATE : 0;
> > diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
> > index de77e31..9970022 100644
> > --- a/fs/ext4/page-io.c
> > +++ b/fs/ext4/page-io.c
> > @@ -71,6 +71,8 @@ void ext4_free_io_end(ext4_io_end_t *io)
> > int i;
> >
> > BUG_ON(!io);
> > + BUG_ON(io->flag & EXT4_IO_END_UNWRITTEN);
> > +
> > if (io->page)
> > put_page(io->page);
> > for (i = 0; i < io->num_io_pages; i++)
> > @@ -94,6 +96,8 @@ int ext4_end_io_nolock(ext4_io_end_t *io)
> > ssize_t size = io->size;
> > int ret = 0;
> >
> > + BUG_ON(!(io->flag & EXT4_IO_END_UNWRITTEN));
> > +
> > ext4_debug("ext4_end_io_nolock: io 0x%p from inode %lu,list->next 0x%p,"
> > "list->prev 0x%p\n",
> > io, inode->i_ino, io->list.next, io->list.prev);
> > @@ -106,7 +110,7 @@ int ext4_end_io_nolock(ext4_io_end_t *io)
> > "(inode %lu, offset %llu, size %zd, error %d)",
> > inode->i_ino, offset, size, ret);
> > }
> > -
> > + io->flag &= ~EXT4_IO_END_UNWRITTEN;
> > if (io->iocb)
> > aio_complete(io->iocb, io->result, 0);
> >
> > --
> > 1.7.7.6
> >
> --
> Jan Kara <jack@xxxxxxx>
> SUSE Labs, CR
> --
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