On 8/16/11 2:06 AM, Tao Ma wrote: > From: Tao Ma <boyu.mt@xxxxxxxxxx> > > EXT4_IO_END_UNWRITTEN flag set and the increase of i_aiodio_unwritten should > be done simultaneously since ext4_end_io_nolock always clear the flag and > decrease the counter in the same time. > > We have found some bugs that the flag is set while leaving i_aiodio_unwritten > unchanged. So this patch just tries to creat a helper function to wrap them > to avoid any future bug. The idea is inspired by Eric. Although I like it a little less now that I see it in practice, sorry. ;) This: /* * Flag the inode(non aio case) or end_io struct (aio case) * that this IO needs to conversion to written when IO is * completed */ if (!ext4_set_io_unwritten_flag(inode, io)) ext4_set_inode_state(inode, EXT4_STATE_DIO_UNWRITTEN); just reads weirdly to me. It encapsulates all the steps, but it really isn't intuitive to read, I think. "If we (can't? don't?) set the io unwritten flag, set the dio unwritten flag on the inode." I wonder if changing "io" to "endio" would make it a little more obvious. I'm not sure, maybe it's ok. What do others think? I also wonder about this, but I get lost in this code. It was originally: if (io && !(io->flag & EXT4_IO_END_UNWRITTEN)) { io->flag = EXT4_IO_END_UNWRITTEN; atomic_inc(&EXT4_I(inode)->i_aiodio_unwritten); } else ext4_set_inode_state(inode, EXT4_STATE_DIO_UNWRITTEN); That means that if it is AIO ("if (io)"), but the flag is already set (io->flag & EXT4_IO_END_UNWRITTEN), we don't re-set the flag or increase the count, which is fine - but is it then correct to set the state on the inode? thanks, -Eric > Cc: Eric Sandeen <sandeen@xxxxxxxxxx> > Cc: "Theodore Ts'o" <tytso@xxxxxxx> > Signed-off-by: Tao Ma <boyu.mt@xxxxxxxxxx> > --- > Ted, > This patch is based on the patch with subject "ext4: Resolve the hang > of direct i/o read in handling EXT4_IO_END_UNWRITTEN.". I meant it for the next > merge window, but if you think it is also ok for 3.1, go ahead. > > fs/ext4/ext4.h | 11 +++++++++++ > fs/ext4/extents.c | 10 ++-------- > fs/ext4/inode.c | 5 +---- > fs/ext4/page-io.c | 6 ++---- > 4 files changed, 16 insertions(+), 16 deletions(-) > > diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h > index e717dfd..514f670 100644 > --- a/fs/ext4/ext4.h > +++ b/fs/ext4/ext4.h > @@ -1247,6 +1247,17 @@ static inline int ext4_valid_inum(struct super_block *sb, unsigned long ino) > ino <= le32_to_cpu(EXT4_SB(sb)->s_es->s_inodes_count)); > } > > +static inline int ext4_set_io_unwritten_flag(struct inode *inode, > + struct ext4_io_end *io_end) > +{ > + if (io_end && !(io_end->flag & EXT4_IO_END_UNWRITTEN)) { > + io_end->flag |= EXT4_IO_END_UNWRITTEN; > + atomic_inc(&EXT4_I(inode)->i_aiodio_unwritten); > + return 1; > + } > + > + return 0; > +} > /* > * Inode dynamic state flags > */ > diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c > index 57cf568..c0f8655 100644 > --- a/fs/ext4/extents.c > +++ b/fs/ext4/extents.c > @@ -3190,10 +3190,7 @@ ext4_ext_handle_uninitialized_extents(handle_t *handle, struct inode *inode, > * that this IO needs to conversion to written when IO is > * completed > */ > - if (io && !(io->flag & EXT4_IO_END_UNWRITTEN)) { > - io->flag = EXT4_IO_END_UNWRITTEN; > - atomic_inc(&EXT4_I(inode)->i_aiodio_unwritten); > - } else > + if (!ext4_set_io_unwritten_flag(inode, io)) > ext4_set_inode_state(inode, EXT4_STATE_DIO_UNWRITTEN); > if (ext4_should_dioread_nolock(inode)) > map->m_flags |= EXT4_MAP_UNINIT; > @@ -3572,10 +3569,7 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode, > * that we need to perform conversion when IO is done. > */ > if ((flags & EXT4_GET_BLOCKS_PRE_IO)) { > - if (io && !(io->flag & EXT4_IO_END_UNWRITTEN)) { > - io->flag = EXT4_IO_END_UNWRITTEN; > - atomic_inc(&EXT4_I(inode)->i_aiodio_unwritten); > - } else > + if (!ext4_set_io_unwritten_flag(inode, io)) > ext4_set_inode_state(inode, > EXT4_STATE_DIO_UNWRITTEN); > } > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c > index 40c0b10..128493b 100644 > --- a/fs/ext4/inode.c > +++ b/fs/ext4/inode.c > @@ -2673,10 +2673,7 @@ static void ext4_end_io_buffer_write(struct buffer_head *bh, int uptodate) > * but being more careful is always safe for the future change. > */ > inode = io_end->inode; > - if (!(io_end->flag & EXT4_IO_END_UNWRITTEN)) { > - io_end->flag |= EXT4_IO_END_UNWRITTEN; > - atomic_inc(&EXT4_I(inode)->i_aiodio_unwritten); > - } > + ext4_set_io_unwritten_flag(inode, io_end); > > /* Add the io_end to per-inode completed io list*/ > spin_lock_irqsave(&EXT4_I(inode)->i_completed_io_lock, flags); > diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c > index 78839af..edd2f7b 100644 > --- a/fs/ext4/page-io.c > +++ b/fs/ext4/page-io.c > @@ -334,10 +334,8 @@ submit_and_retry: > if ((io_end->num_io_pages >= MAX_IO_PAGES) && > (io_end->pages[io_end->num_io_pages-1] != io_page)) > goto submit_and_retry; > - if (buffer_uninit(bh) && !(io_end->flag & EXT4_IO_END_UNWRITTEN)) { > - io_end->flag |= EXT4_IO_END_UNWRITTEN; > - atomic_inc(&EXT4_I(inode)->i_aiodio_unwritten); > - } > + if (buffer_uninit(bh)) > + ext4_set_io_unwritten_flag(inode, io_end); > io->io_end->size += bh->b_size; > io->io_next_block++; > ret = bio_add_page(io->io_bio, bh->b_page, bh->b_size, bh_offset(bh)); -- 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