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Re: [PATCH] xfs: improve kmem_realloc

To: Christoph Hellwig <hch@xxxxxx>
Subject: Re: [PATCH] xfs: improve kmem_realloc
From: Brian Foster <bfoster@xxxxxxxxxx>
Date: Mon, 28 Mar 2016 06:46:55 -0400
Cc: xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1458740836-31211-1-git-send-email-hch@xxxxxx>
References: <1458740836-31211-1-git-send-email-hch@xxxxxx>
User-agent: Mutt/1.5.24 (2015-08-30)
On Wed, Mar 23, 2016 at 02:47:16PM +0100, Christoph Hellwig wrote:
> Use krealloc to implement our realloc function.  This helps to avoid
> new allocations if we are still in the slab bucket.  At least for the
> bmap btree root that's actually the common case.
> 
> This also allows removing the now unused oldsize argument.
> 
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---

Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>

>  fs/xfs/kmem.c                  | 26 +++++++++++++++-----------
>  fs/xfs/kmem.h                  |  2 +-
>  fs/xfs/libxfs/xfs_inode_fork.c | 10 +++-------
>  fs/xfs/xfs_log_recover.c       |  2 +-
>  fs/xfs/xfs_mount.c             |  1 -
>  5 files changed, 20 insertions(+), 21 deletions(-)
> 
> diff --git a/fs/xfs/kmem.c b/fs/xfs/kmem.c
> index 686ba6f..339c696 100644
> --- a/fs/xfs/kmem.c
> +++ b/fs/xfs/kmem.c
> @@ -93,19 +93,23 @@ kmem_zalloc_large(size_t size, xfs_km_flags_t flags)
>  }
>  
>  void *
> -kmem_realloc(const void *ptr, size_t newsize, size_t oldsize,
> -          xfs_km_flags_t flags)
> +kmem_realloc(const void *old, size_t newsize, xfs_km_flags_t flags)
>  {
> -     void    *new;
> +     int     retries = 0;
> +     gfp_t   lflags = kmem_flags_convert(flags);
> +     void    *ptr;
>  
> -     new = kmem_alloc(newsize, flags);
> -     if (ptr) {
> -             if (new)
> -                     memcpy(new, ptr,
> -                             ((oldsize < newsize) ? oldsize : newsize));
> -             kmem_free(ptr);
> -     }
> -     return new;
> +     do {
> +             ptr = krealloc(old, newsize, lflags);
> +             if (ptr || (flags & (KM_MAYFAIL|KM_NOSLEEP)))
> +                     return ptr;
> +             if (!(++retries % 100))
> +                     xfs_err(NULL,
> +     "%s(%u) possible memory allocation deadlock size %zu in %s (mode:0x%x)",
> +                             current->comm, current->pid,
> +                             newsize, __func__, lflags);
> +             congestion_wait(BLK_RW_ASYNC, HZ/50);
> +     } while (1);
>  }
>  
>  void *
> diff --git a/fs/xfs/kmem.h b/fs/xfs/kmem.h
> index d1c66e4..689f746 100644
> --- a/fs/xfs/kmem.h
> +++ b/fs/xfs/kmem.h
> @@ -62,7 +62,7 @@ kmem_flags_convert(xfs_km_flags_t flags)
>  
>  extern void *kmem_alloc(size_t, xfs_km_flags_t);
>  extern void *kmem_zalloc_large(size_t size, xfs_km_flags_t);
> -extern void *kmem_realloc(const void *, size_t, size_t, xfs_km_flags_t);
> +extern void *kmem_realloc(const void *, size_t, xfs_km_flags_t);
>  static inline void  kmem_free(const void *ptr)
>  {
>       kvfree(ptr);
> diff --git a/fs/xfs/libxfs/xfs_inode_fork.c b/fs/xfs/libxfs/xfs_inode_fork.c
> index 4fbe226..d3d1477 100644
> --- a/fs/xfs/libxfs/xfs_inode_fork.c
> +++ b/fs/xfs/libxfs/xfs_inode_fork.c
> @@ -542,7 +542,6 @@ xfs_iroot_realloc(
>               new_max = cur_max + rec_diff;
>               new_size = XFS_BMAP_BROOT_SPACE_CALC(mp, new_max);
>               ifp->if_broot = kmem_realloc(ifp->if_broot, new_size,
> -                             XFS_BMAP_BROOT_SPACE_CALC(mp, cur_max),
>                               KM_SLEEP | KM_NOFS);
>               op = (char *)XFS_BMAP_BROOT_PTR_ADDR(mp, ifp->if_broot, 1,
>                                                    ifp->if_broot_bytes);
> @@ -686,7 +685,6 @@ xfs_idata_realloc(
>                               ifp->if_u1.if_data =
>                                       kmem_realloc(ifp->if_u1.if_data,
>                                                       real_size,
> -                                                     ifp->if_real_bytes,
>                                                       KM_SLEEP | KM_NOFS);
>                       }
>               } else {
> @@ -1402,8 +1400,7 @@ xfs_iext_realloc_direct(
>               if (rnew_size != ifp->if_real_bytes) {
>                       ifp->if_u1.if_extents =
>                               kmem_realloc(ifp->if_u1.if_extents,
> -                                             rnew_size,
> -                                             ifp->if_real_bytes, KM_NOFS);
> +                                             rnew_size, KM_NOFS);
>               }
>               if (rnew_size > ifp->if_real_bytes) {
>                       memset(&ifp->if_u1.if_extents[ifp->if_bytes /
> @@ -1487,9 +1484,8 @@ xfs_iext_realloc_indirect(
>       if (new_size == 0) {
>               xfs_iext_destroy(ifp);
>       } else {
> -             ifp->if_u1.if_ext_irec = (xfs_ext_irec_t *)
> -                     kmem_realloc(ifp->if_u1.if_ext_irec,
> -                             new_size, size, KM_NOFS);
> +             ifp->if_u1.if_ext_irec =
> +                     kmem_realloc(ifp->if_u1.if_ext_irec, new_size, KM_NOFS);
>       }
>  }
>  
> diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
> index 396565f..bf6e807 100644
> --- a/fs/xfs/xfs_log_recover.c
> +++ b/fs/xfs/xfs_log_recover.c
> @@ -3843,7 +3843,7 @@ xlog_recover_add_to_cont_trans(
>       old_ptr = item->ri_buf[item->ri_cnt-1].i_addr;
>       old_len = item->ri_buf[item->ri_cnt-1].i_len;
>  
> -     ptr = kmem_realloc(old_ptr, len+old_len, old_len, KM_SLEEP);
> +     ptr = kmem_realloc(old_ptr, len + old_len, KM_SLEEP);
>       memcpy(&ptr[old_len], dp, len);
>       item->ri_buf[item->ri_cnt-1].i_len += len;
>       item->ri_buf[item->ri_cnt-1].i_addr = ptr;
> diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
> index 536a0ee..654799f 100644
> --- a/fs/xfs/xfs_mount.c
> +++ b/fs/xfs/xfs_mount.c
> @@ -89,7 +89,6 @@ xfs_uuid_mount(
>       if (hole < 0) {
>               xfs_uuid_table = kmem_realloc(xfs_uuid_table,
>                       (xfs_uuid_table_size + 1) * sizeof(*xfs_uuid_table),
> -                     xfs_uuid_table_size  * sizeof(*xfs_uuid_table),
>                       KM_SLEEP);
>               hole = xfs_uuid_table_size++;
>       }
> -- 
> 2.1.4
> 
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