On 08/16/2011 10:04 PM, Eric Sandeen wrote: > 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. yeah, this also looks a little bit strange. Another possible way is that we just wrap the set of the flag and the inc of aiodio_unwritten while leave the check there. It should look more natural and good for the reader. > > 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? I will check it later. Thanks Tao > > 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