linux-kernel - Re: [PATCH] ceph: only allow punch hole mode in fallocate

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Date:   Wed, 10 Oct 2018 12:20:57 +0800
From:   "Yan, Zheng" <ukernel@...il.com>
To:     Luis Henriques <lhenriques@...e.com>
Cc:     Zheng Yan <zyan@...hat.com>, Sage Weil <sage@...hat.com>,
        Ilya Dryomov <idryomov@...il.com>,
        ceph-devel <ceph-devel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ceph: only allow punch hole mode in fallocate

On Wed, Oct 10, 2018 at 1:54 AM Luis Henriques <lhenriques@...e.com> wrote:
>
> Current implementation of cephfs fallocate isn't correct as it doesn't
> really reserve the space in the cluster, which means that a subsequent
> call to a write may actually fail due to lack of space.  In fact, it is
> currently possible to fallocate an amount space that is larger than the
> free space in the cluster.
>
> Since there's no easy solution to fix this at the moment, this patch
> simply removes support for all fallocate operations but
> FALLOC_FL_PUNCH_HOLE (which implies FALLOC_FL_KEEP_SIZE).
>
> Link: https://tracker.ceph.com/issues/36317
> Cc: stable@...r.kernel.org
> Fixes: ad7a60de882a ("ceph: punch hole support")
> Signed-off-by: Luis Henriques <lhenriques@...e.com>
> ---
>  fs/ceph/file.c | 45 +++++++++------------------------------------
>  1 file changed, 9 insertions(+), 36 deletions(-)
>
> diff --git a/fs/ceph/file.c b/fs/ceph/file.c
> index 92ab20433682..91a7ad259bcf 100644
> --- a/fs/ceph/file.c
> +++ b/fs/ceph/file.c
> @@ -1735,7 +1735,6 @@ static long ceph_fallocate(struct file *file, int mode,
>         struct ceph_file_info *fi = file->private_data;
>         struct inode *inode = file_inode(file);
>         struct ceph_inode_info *ci = ceph_inode(inode);
> -       struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
>         struct ceph_cap_flush *prealloc_cf;
>         int want, got = 0;
>         int dirty;
> @@ -1743,10 +1742,7 @@ static long ceph_fallocate(struct file *file, int mode,
>         loff_t endoff = 0;
>         loff_t size;
>
> -       if ((offset + length) > max(i_size_read(inode), fsc->max_file_size))
> -               return -EFBIG;
> -
> -       if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
> +       if (mode != (FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
>                 return -EOPNOTSUPP;
>
>         if (!S_ISREG(inode->i_mode))
> @@ -1763,18 +1759,6 @@ static long ceph_fallocate(struct file *file, int mode,
>                 goto unlock;
>         }
>
> -       if (!(mode & (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE)) &&
> -           ceph_quota_is_max_bytes_exceeded(inode, offset + length)) {
> -               ret = -EDQUOT;
> -               goto unlock;
> -       }
> -
> -       if (ceph_osdmap_flag(&fsc->client->osdc, CEPH_OSDMAP_FULL) &&
> -           !(mode & FALLOC_FL_PUNCH_HOLE)) {
> -               ret = -ENOSPC;
> -               goto unlock;
> -       }
> -
>         if (ci->i_inline_version != CEPH_INLINE_NONE) {
>                 ret = ceph_uninline_data(file, NULL);
>                 if (ret < 0)
> @@ -1782,12 +1766,12 @@ static long ceph_fallocate(struct file *file, int mode,
>         }
>
>         size = i_size_read(inode);
> -       if (!(mode & FALLOC_FL_KEEP_SIZE)) {
> -               endoff = offset + length;
> -               ret = inode_newsize_ok(inode, endoff);
> -               if (ret)
> -                       goto unlock;
> -       }
> +
> +       /* Are we punching a hole beyond EOF? */
> +       if (offset >= size)
> +               goto unlock;
> +       if ((offset + length) > size)
> +               length = size - offset;
>
>         if (fi->fmode & CEPH_FILE_MODE_LAZY)
>                 want = CEPH_CAP_FILE_BUFFER | CEPH_CAP_FILE_LAZYIO;
> @@ -1798,16 +1782,8 @@ static long ceph_fallocate(struct file *file, int mode,
>         if (ret < 0)
>                 goto unlock;
>
> -       if (mode & FALLOC_FL_PUNCH_HOLE) {
> -               if (offset < size)
> -                       ceph_zero_pagecache_range(inode, offset, length);
> -               ret = ceph_zero_objects(inode, offset, length);
> -       } else if (endoff > size) {
> -               truncate_pagecache_range(inode, size, -1);
> -               if (ceph_inode_set_size(inode, endoff))
> -                       ceph_check_caps(ceph_inode(inode),
> -                               CHECK_CAPS_AUTHONLY, NULL);
> -       }
> +       ceph_zero_pagecache_range(inode, offset, length);
> +       ret = ceph_zero_objects(inode, offset, length);
>
>         if (!ret) {
>                 spin_lock(&ci->i_ceph_lock);
> @@ -1817,9 +1793,6 @@ static long ceph_fallocate(struct file *file, int mode,
>                 spin_unlock(&ci->i_ceph_lock);
>                 if (dirty)
>                         __mark_inode_dirty(inode, dirty);
> -               if ((endoff > size) &&
> -                   ceph_quota_is_max_bytes_approaching(inode, endoff))
> -                       ceph_check_caps(ci, CHECK_CAPS_NODELAY, NULL);
>         }
>
>         ceph_put_cap_refs(ci, got);

Applied, thanks

Yan, Zheng