On 4/23/20 2:34 PM, Eric Sandeen wrote:
> This scenario is the source of much confusion for admins and
> support folks alike:
>
> # touch mnt/newfile
> touch: cannot touch ‘mnt/newfile’: No space left on device
> # df -h mnt
> Filesystem Size Used Avail Use% Mounted on
> /dev/loop0 196M 137M 59M 71% /tmp/mnt
> # df -i mnt/
> Filesystem Inodes IUsed IFree IUse% Mounted on
> /dev/loop0 102400 64256 38144 63% /tmp/mnt
>
> because it appears that there is plenty of space available, yet ENOSPC
> is returned.
>
> Track this case in the allocation args structure, and when an allocation
> fails due to alignment constraints, leave a clue in the kernel logs:
>
> XFS (loop0): Failed metadata allocation due to 4-block alignment constraint
Welp, I always realize what's wrong with the patch right after I send it;
I think this reports the failure on each AG that fails, even if a later
AG succeeds so I need to get the result up to a higher level.
Still, can see what people think of the idea in general?
Thanks,
-Eric
> Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
> ---
>
> Right now this depends on my "printk_once" patch but you can change
> xfs_warn_once to xfs_warn or xfs_warn_ratelimited for testing.
>
> Perhaps a 2nd patch to log a similar message if alignment failed due to
> /contiguous/ free space constraints would be good as well?
>
> diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
> index 203e74fa64aa..10f32797e5ca 100644
> --- a/fs/xfs/libxfs/xfs_alloc.c
> +++ b/fs/xfs/libxfs/xfs_alloc.c
> @@ -2303,8 +2303,12 @@ xfs_alloc_space_available(
> /* do we have enough contiguous free space for the allocation? */
> alloc_len = args->minlen + (args->alignment - 1) + args->minalignslop;
> longest = xfs_alloc_longest_free_extent(pag, min_free, reservation);
> - if (longest < alloc_len)
> + if (longest < alloc_len) {
> + /* Did we fail only due to alignment? */
> + if (longest >= args->minlen)
> + args->alignfail = 1;
> return false;
> + }
>
> /*
> * Do we have enough free space remaining for the allocation? Don't
> @@ -3067,8 +3071,10 @@ xfs_alloc_vextent(
> agsize = mp->m_sb.sb_agblocks;
> if (args->maxlen > agsize)
> args->maxlen = agsize;
> - if (args->alignment == 0)
> + if (args->alignment == 0) {
> args->alignment = 1;
> + args->alignfail = 0;
> + }
> ASSERT(XFS_FSB_TO_AGNO(mp, args->fsbno) < mp->m_sb.sb_agcount);
> ASSERT(XFS_FSB_TO_AGBNO(mp, args->fsbno) < agsize);
> ASSERT(args->minlen <= args->maxlen);
> @@ -3227,6 +3233,13 @@ xfs_alloc_vextent(
>
> }
> xfs_perag_put(args->pag);
> + if (!args->agbp && args->alignment > 1 && args->alignfail) {
> + xfs_warn_once(args->mp,
> +"Failed %s allocation due to %u-block alignment constraint",
> + XFS_RMAP_NON_INODE_OWNER(args->oinfo.oi_owner) ?
> + "metadata" : "data",
> + args->alignment);
> + }
> return 0;
> error0:
> xfs_perag_put(args->pag);
> diff --git a/fs/xfs/libxfs/xfs_alloc.h b/fs/xfs/libxfs/xfs_alloc.h
> index a851bf77f17b..29d13cd5c9ac 100644
> --- a/fs/xfs/libxfs/xfs_alloc.h
> +++ b/fs/xfs/libxfs/xfs_alloc.h
> @@ -73,6 +73,7 @@ typedef struct xfs_alloc_arg {
> int datatype; /* mask defining data type treatment */
> char wasdel; /* set if allocation was prev delayed */
> char wasfromfl; /* set if allocation is from freelist */
> + char alignfail; /* set if alloc failed due to alignmt */
> struct xfs_owner_info oinfo; /* owner of blocks being allocated */
> enum xfs_ag_resv_type resv; /* block reservation to use */
> } xfs_alloc_arg_t;
> diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
> index fda13cd7add0..808060649cad 100644
> --- a/fs/xfs/libxfs/xfs_bmap.c
> +++ b/fs/xfs/libxfs/xfs_bmap.c
> @@ -3563,6 +3563,7 @@ xfs_bmap_btalloc(
> args.mp = mp;
> args.fsbno = ap->blkno;
> args.oinfo = XFS_RMAP_OINFO_SKIP_UPDATE;
> + args.alignfail = 0;
>
> /* Trim the allocation back to the maximum an AG can fit. */
> args.maxlen = min(ap->length, mp->m_ag_max_usable);
> diff --git a/fs/xfs/libxfs/xfs_ialloc.c b/fs/xfs/libxfs/xfs_ialloc.c
> index 7fcf62b324b0..e98dcb8e65eb 100644
> --- a/fs/xfs/libxfs/xfs_ialloc.c
> +++ b/fs/xfs/libxfs/xfs_ialloc.c
> @@ -685,6 +685,7 @@ xfs_ialloc_ag_alloc(
> * but not to use them in the actual exact allocation.
> */
> args.alignment = 1;
> + args.alignfail = 0;
> args.minalignslop = igeo->cluster_align - 1;
>
> /* Allow space for the inode btree to split. */
>
