| Message ID | 1313476673-4866-1-git-send-email-tm@tao.ma |
|---|---|
| State | Accepted, archived |
| Headers | show |
On 8/16/11 1:37 AM, Tao Ma wrote: > From: Tao Ma <boyu.mt@taobao.com> > > 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 don't increase i_aiodio_unwritten when setting EXT4_IO_END_UNWRITTEN so > it will go nagative and causes some process to wait forever. > > Part of the patch came from Eric in his e-mail, but it doesn't fix the problem > met by Michael actually. > http://marc.info/?l=linux-ext4&m=131316851417460&w=2 > > Reported-and-Tested-by: Michael Tokarev<mjt@tls.msk.ru> > Signed-off-by: Eric Sandeen <sandeen@redhat.com> > Signed-off-by: Tao Ma <boyu.mt@taobao.com> Yes, this looks right to me. It's the patch I meant to send, but I missed one spot in my haste. ;) Thanks. -Eric > --- > Eric talked about creating a helper for this and I feel that it looks > like a new functionality not a bug fix and decided to leave it to the > next merge window. > > fs/ext4/inode.c | 9 ++++++++- > fs/ext4/page-io.c | 6 ++++-- > 2 files changed, 12 insertions(+), 3 deletions(-) > > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c > index d47264c..40c0b10 100644 > --- a/fs/ext4/inode.c > +++ b/fs/ext4/inode.c > @@ -2668,8 +2668,15 @@ static void ext4_end_io_buffer_write(struct buffer_head *bh, int uptodate) > goto out; > } > > - io_end->flag = EXT4_IO_END_UNWRITTEN; > + /* > + * It may be over-defensive here to check EXT4_IO_END_UNWRITTEN now, > + * 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); > + } > > /* 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 430c401..78839af 100644 > --- a/fs/ext4/page-io.c > +++ b/fs/ext4/page-io.c > @@ -334,8 +334,10 @@ 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->io_end->flag |= EXT4_IO_END_UNWRITTEN; > + 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); > + } > 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@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Aug 16, 2011 at 02:37:53PM +0800, Tao Ma wrote: > From: Tao Ma <boyu.mt@taobao.com> > > 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 don't increase i_aiodio_unwritten when setting EXT4_IO_END_UNWRITTEN so > it will go nagative and causes some process to wait forever. > > Part of the patch came from Eric in his e-mail, but it doesn't fix the problem > met by Michael actually. > http://marc.info/?l=linux-ext4&m=131316851417460&w=2 > > Reported-and-Tested-by: Michael Tokarev<mjt@tls.msk.ru> > Signed-off-by: Eric Sandeen <sandeen@redhat.com> > Signed-off-by: Tao Ma <boyu.mt@taobao.com> Thanks I've taken this into the ext4 tree. I am a bit worried this will trigger a GCC warning: + /* + * It may be over-defensive here to check EXT4_IO_END_UNWRITTEN now, + * 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); + } /* Add the io_end to per-inode completed io list*/ spin_lock_irqsave(&EXT4_I(inode)->i_completed_io_lock, flags); ... since in Google we've been compiling with -Werror, but it's not causing an error on gcc 4.4, which is what I still have on my laptop. It may be that newer versions of GCC are smart enough to notice tha the above is dead code, and then complain with a warning. - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 08/17/2011 02:29 AM, Ted Ts'o wrote: > On Tue, Aug 16, 2011 at 02:37:53PM +0800, Tao Ma wrote: >> From: Tao Ma <boyu.mt@taobao.com> >> >> 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 don't increase i_aiodio_unwritten when setting EXT4_IO_END_UNWRITTEN so >> it will go nagative and causes some process to wait forever. >> >> Part of the patch came from Eric in his e-mail, but it doesn't fix the problem >> met by Michael actually. >> http://marc.info/?l=linux-ext4&m=131316851417460&w=2 >> >> Reported-and-Tested-by: Michael Tokarev<mjt@tls.msk.ru> >> Signed-off-by: Eric Sandeen <sandeen@redhat.com> >> Signed-off-by: Tao Ma <boyu.mt@taobao.com> > > Thanks I've taken this into the ext4 tree. I am a bit worried this > will trigger a GCC warning: > > + /* > + * It may be over-defensive here to check EXT4_IO_END_UNWRITTEN now, > + * 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); > + } > > /* Add the io_end to per-inode completed io list*/ > spin_lock_irqsave(&EXT4_I(inode)->i_completed_io_lock, flags); > > ... since in Google we've been compiling with -Werror, but it's not > causing an error on gcc 4.4, which is what I still have on my laptop. > It may be that newer versions of GCC are smart enough to notice tha > the above is dead code, and then complain with a warning. Sorry for my bluntness. But where is the 'dead code' you mean? Thanks Tao -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index d47264c..40c0b10 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -2668,8 +2668,15 @@ static void ext4_end_io_buffer_write(struct buffer_head *bh, int uptodate) goto out; } - io_end->flag = EXT4_IO_END_UNWRITTEN; + /* + * It may be over-defensive here to check EXT4_IO_END_UNWRITTEN now, + * 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); + } /* 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 430c401..78839af 100644 --- a/fs/ext4/page-io.c +++ b/fs/ext4/page-io.c @@ -334,8 +334,10 @@ 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->io_end->flag |= EXT4_IO_END_UNWRITTEN; + 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); + } 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));