On Wed, Apr 17, 2024 at 08:07:35PM +0800, alexjlzheng@xxxxxxxxx wrote:
> From: Jinliang Zheng <alexjlzheng@xxxxxxxxxxx>
>
> Historically, when generic percpu counters were introduced in xfs for
> free block counters by commit 0d485ada404b ("xfs: use generic percpu
> counters for free block counter"), the counters used a custom batch
> size. In xfs_mod_freecounter(), originally named xfs_mod_fdblocks(),
> this patch attempted to serialize the program using a smaller batch size
> as parameter to the addition function as the counter approaches 0.
>
> Commit 8c1903d3081a ("xfs: inode and free block counters need to use
> __percpu_counter_compare") pointed out the error in commit 0d485ada404b
> ("xfs: use generic percpu counters for free block counter") mentioned
> above and said that "Because the counters use a custom batch size, the
> comparison functions need to be aware of that batch size otherwise the
> comparison does not work correctly". Then percpu_counter_compare() was
> replaced with __percpu_counter_compare() with parameter
> XFS_FDBLOCKS_BATCH.
>
> After commit 8c1903d3081a ("xfs: inode and free block counters need to
> use __percpu_counter_compare"), the existence of the batch variable is
> no longer necessary, so this patch is proposed to simplify the code by
> removing it.
>
> Signed-off-by: Jinliang Zheng <alexjlzheng@xxxxxxxxxxx>
> ---
> Changelog:
>
> v3: Resend for the second time
>
> v2: https://lore.kernel.org/linux-xfs/20230918043344.890817-1-alexjlzheng@xxxxxxxxxxx/
>
> v1: https://lore.kernel.org/linux-xfs/20230908235713.GP28202@frogsfrogsfrogs/T/#t
...you still haven't answered my question from V1: What problem are you
solving with this patch?
--D
> ---
> fs/xfs/xfs_mount.c | 17 +----------------
> 1 file changed, 1 insertion(+), 16 deletions(-)
>
> diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
> index aed5be5508fe..8e47a3040893 100644
> --- a/fs/xfs/xfs_mount.c
> +++ b/fs/xfs/xfs_mount.c
> @@ -1144,7 +1144,6 @@ xfs_mod_freecounter(
> int64_t lcounter;
> long long res_used;
> uint64_t set_aside = 0;
> - s32 batch;
> bool has_resv_pool;
>
> ASSERT(counter == &mp->m_fdblocks || counter == &mp->m_frextents);
> @@ -1177,20 +1176,6 @@ xfs_mod_freecounter(
> return 0;
> }
>
> - /*
> - * Taking blocks away, need to be more accurate the closer we
> - * are to zero.
> - *
> - * If the counter has a value of less than 2 * max batch size,
> - * then make everything serialise as we are real close to
> - * ENOSPC.
> - */
> - if (__percpu_counter_compare(counter, 2 * XFS_FDBLOCKS_BATCH,
> - XFS_FDBLOCKS_BATCH) < 0)
> - batch = 1;
> - else
> - batch = XFS_FDBLOCKS_BATCH;
> -
> /*
> * Set aside allocbt blocks because these blocks are tracked as free
> * space but not available for allocation. Technically this means that a
> @@ -1204,7 +1189,7 @@ xfs_mod_freecounter(
> */
> if (has_resv_pool)
> set_aside = xfs_fdblocks_unavailable(mp);
> - percpu_counter_add_batch(counter, delta, batch);
> + percpu_counter_add_batch(counter, delta, XFS_FDBLOCKS_BATCH);
> if (__percpu_counter_compare(counter, set_aside,
> XFS_FDBLOCKS_BATCH) >= 0) {
> /* we had space! */
> --
> 2.39.3
>
>
