On Thu, May 22, 2008 at 11:10:17AM -0700, Mingming wrote:
>
> On Wed, 2008-05-21 at 23:14 +0530, Aneesh Kumar K.V wrote:
> > Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
> > ---
> > fs/ext4/inode.c | 10 +++++++---
> > 1 files changed, 7 insertions(+), 3 deletions(-)
> >
> > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> > index 46cc610..076d00f 100644
> > --- a/fs/ext4/inode.c
> > +++ b/fs/ext4/inode.c
> > @@ -1571,13 +1571,17 @@ static int ext4_da_writepages(struct address_space *mapping,
> > */
> > if (wbc->nr_to_write > EXT4_MAX_WRITEBACK_PAGES)
> > wbc->nr_to_write = EXT4_MAX_WRITEBACK_PAGES;
> > - to_write -= wbc->nr_to_write;
> >
> > + to_write -= wbc->nr_to_write;
> > ret = mpage_da_writepages(mapping, wbc, ext4_da_get_block_write);
> > ext4_journal_stop(handle);
> > - to_write +=wbc->nr_to_write;
> > + if (wbc->nr_to_write) {
> > + /* We failed to write what we requested for */
> > + to_write += wbc->nr_to_write;
> > + break;
> > + }
>
> Not sure about the break here...
> > + wbc->nr_to_write = to_write;
>
> Looks right. thanks.
>
> > }
> > -
> > out_writepages:
> > wbc->nr_to_write = to_write;
> > wbc->range_cyclic = range_cyclic;
>
The call chain that made me look at this was
#0 ext4_da_writepages (mapping=0xc76dc244, wbc=0xc790bf70) at fs/ext4/inode.c:1557
#1 0xc0150176 in do_writepages (mapping=0xc76dc244, wbc=0xc790bf70) at mm/page-writeback.c:1004
#2 0xc0180fe6 in __writeback_single_inode (inode=0xc76dc11c, wbc=0xc790bf70) at fs/fs-writeback.c:285
#3 0xc018146c in sync_sb_inodes (sb=0xc7abac00, wbc=0xc790bf70) at fs/fs-writeback.c:502
#4 0xc0181701 in writeback_inodes (wbc=0xc790bf70) at fs/fs-writeback.c:570
#5 0xc01509f8 in background_writeout (_min_pages=<value optimized out>) at mm/page-writeback.c:639
#6 0xc0150f57 in pdflush (dummy=<value optimized out>) at mm/pdflush.c:127
#7 0xc01324af in kthread (_create=<value optimized out>) at kernel/kthread.c:79
#8 0xc0104633 in kernel_thread_helper () at include/asm/string_32.h:238
ext4_da_writepages gets called with nr_to_write MAX_WRITEBACK_PAGES. the
file size is only 4K. ie there is only one page to write. With these
value we get stuck in the above loop because to_write will never decrement
below 1023.
-aneesh
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