On 2011-06-28, at 9:33 AM, Josef Bacik wrote:
> Since Ext4 has its own lseek we need to make sure it handles
> SEEK_HOLE/SEEK_DATA. For now just do the same thing that is done in the generic
> case, somebody else can come along and make it do fancy things later. Thanks,
Josef,
are you planning to add an ext4-based version of this in the future?
Another possibility is to have a generic SEEK_{DATA,HOLE} -> FIEMAP
converter, since there are several filesystems that already support
FIEMAP (ext3, ext4, etc).
> Signed-off-by: Josef Bacik <[email protected]>
> ---
> fs/ext4/file.c | 21 +++++++++++++++++++++
> 1 files changed, 21 insertions(+), 0 deletions(-)
>
> diff --git a/fs/ext4/file.c b/fs/ext4/file.c
> index 2c09723..ce766f9 100644
> --- a/fs/ext4/file.c
> +++ b/fs/ext4/file.c
> @@ -236,6 +236,27 @@ loff_t ext4_llseek(struct file *file, loff_t offset, int origin)
> }
> offset += file->f_pos;
> break;
> + case SEEK_DATA:
> + /*
> + * In the generic case the entire file is data, so as long as
> + * offset isn't at the end of the file then the offset is data.
> + */
> + if (offset >= inode->i_size) {
> + mutex_unlock(&inode->i_mutex);
> + return -ENXIO;
> + }
> + break;
> + case SEEK_HOLE:
> + /*
> + * There is a virtual hole at the end of the file, so as long as
> + * offset isn't i_size or larger, return i_size.
> + */
> + if (offset >= inode->i_size) {
> + mutex_unlock(&inode->i_mutex);
> + return -ENXIO;
> + }
> + offset = inode->i_size;
> + break;
> }
>
> if (offset < 0 || offset > maxbytes) {
> --
> 1.7.5.2
>
> --
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Cheers, Andreas
On 06/28/2011 12:29 PM, Andreas Dilger wrote:
> On 2011-06-28, at 9:33 AM, Josef Bacik wrote:
>> Since Ext4 has its own lseek we need to make sure it handles
>> SEEK_HOLE/SEEK_DATA. For now just do the same thing that is done in the generic
>> case, somebody else can come along and make it do fancy things later. Thanks,
>
> Josef,
> are you planning to add an ext4-based version of this in the future?
> Another possibility is to have a generic SEEK_{DATA,HOLE} -> FIEMAP
> converter, since there are several filesystems that already support
> FIEMAP (ext3, ext4, etc).
Probably not, I'm pretty tied up in Btrfs work. I had thought about
doing a generic one that used fiemap but that's a lot of work and I'm
lazy :). Plus everybody who does fiemap all have different answers on
what is a hole. For example btrfs can safely say prealloc'ed space is a
hole, but xfs can't (and I *think* ext4 can't either but I'm not sure).
So I figured just leaving it up to each individual fs'es instead of
hobbling together a generic fiemap->seek_hole/data translator was more
prudent, especially since everybody will eventually want to do their own
thing. Thanks,
Josef