在 2008-08-29五的 09:44 +0530，Aneesh Kumar K.V写道：
> On Fri, Aug 29, 2008 at 09:14:51AM +0530, Aneesh Kumar K.V wrote:
> > On Thu, Aug 28, 2008 at 02:57:49PM -0700, Mingming Cao wrote:
> > >
> > > From: Mingming Cao <cmm@xxxxxxxxxx>
> > >
> > > ext4: Fix ext4 nomballoc allocator for ENOSPC
> > >
> > > We run into ENOSPC error on nonmballoc ext4, even when there is free blocks
> > > on the filesystem.
> > >
> > > The problem is triggered in the case the goal block group has 0 free blocks
> > > , and the rest block groups are skipped due to the check of "free_blocks
> > > < windowsz/2".
> >
> > The goal block group had free blocks < windowsz .
> >
> >
>
> Ok how about this. The Final change is same to what you have done.
> But it make the code easier to understand. I also added a comment
> explaining the details
>
Fine with me, I will update the patch in the ext4 patch queue with
additional comment. But Andrew has already took ext2/3 version to mm
tree, I am not sure if it worth to resend with an patch against original
patch.
> commit 0216ee1ac13270c1ab7b7517d41775727f7da02d
> Author: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
> Date: Fri Aug 29 09:35:15 2008 +0530
>
> ext4: Fix ext4 nomballoc allocator for ENOSPC
>
> We run into ENOSPC error on nonmballoc ext4, even when there is free blocks
> on the filesystem.
>
> The patch include two changes
>
> a) Set reservation to NULL if we trying to allocate near group_target_block
> from the goal group if the free block in the group is less than windowsz.
> This should give us a better chance to allocate near group_target_block.
> This also ensures that if we are not allocating near group_target_block
> then we don't trun off reservation. This should enable us to allocate
> with reservation from other groups that have large free blocks count.
>
> b) we don't need to check the window size if the block reservation is off.
>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Mingming Cao <cmm@xxxxxxxxxx>
>
> diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
> index cfe01b4..399bec5 100644
> --- a/fs/ext4/balloc.c
> +++ b/fs/ext4/balloc.c
> @@ -1802,15 +1802,17 @@ ext4_fsblk_t ext4_old_new_blocks(handle_t *handle, struct inode *inode,
> goto io_error;
>
> free_blocks = le16_to_cpu(gdp->bg_free_blocks_count);
> - /*
> - * if there is not enough free blocks to make a new resevation
> - * turn off reservation for this allocation
> - */
> - if (my_rsv && (free_blocks < windowsz)
> - && (rsv_is_empty(&my_rsv->rsv_window)))
> - my_rsv = NULL;
>
> if (free_blocks > 0) {
> + /*
> + * try to allocate with group target block
> + * in the goal group. If we have low free_blocks
> + * count turn off reservation
> + */
> + if (my_rsv && (free_blocks < windowsz)
> + && (rsv_is_empty(&my_rsv->rsv_window)))
> + my_rsv = NULL;
> +
> bitmap_bh = ext4_read_block_bitmap(sb, group_no);
> if (!bitmap_bh)
> goto io_error;
> @@ -1843,7 +1845,7 @@ ext4_fsblk_t ext4_old_new_blocks(handle_t *handle, struct inode *inode,
> * free blocks is less than half of the reservation
> * window size.
> */
> - if (free_blocks <= (windowsz/2))
> + if (my_rsv && (free_blocks <= (windowsz/2)))
> continue;
>
> brelse(bitmap_bh);
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