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SubjectRe: [PATCH 4/6] Ext4: fail if we try to use hole punch
On 15/11/10 17:05, Josef Bacik wrote:
> Ext4 doesn't have the ability to punch holes yet, so make sure we return
> EOPNOTSUPP if we try to use hole punching through fallocate. This support can
> be added later. Thanks,
>
> Signed-off-by: Josef Bacik <josef@redhat.com>
> ---
> fs/ext4/extents.c | 4 ++++
> 1 files changed, 4 insertions(+), 0 deletions(-)
>
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index 0554c48..35bca73 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -3622,6 +3622,10 @@ long ext4_fallocate(struct inode *inode, int mode, loff_t offset, loff_t len)
> struct ext4_map_blocks map;
> unsigned int credits, blkbits = inode->i_blkbits;
>
> + /* We only support the FALLOC_FL_KEEP_SIZE mode */
> + if (mode && (mode != FALLOC_FL_KEEP_SIZE))
> + return -EOPNOTSUPP;
> +
> /*
> * currently supporting (pre)allocate mode for extent-based
> * files _only_

So for older versions of ext4 or other filesystems, how do we know
that fallocate(...,FALLOC_FL_PUNCH_HOLE) is not supported.
I.E. how do we detect at runtime that the call succeeded
and didn't just do a normal fallocate()?

cheers,
Pádraig.
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