On Wed, 26 Feb 2014, jon ernst wrote:
> Date: Wed, 26 Feb 2014 23:41:15 -0500
> From: jon ernst <jonernst07@xxxxxxxxx>
> To: Lukas Czerner <lczerner@xxxxxxxxxx>
> Cc: "linux-ext4@xxxxxxxxxxxxxxx List" <linux-ext4@xxxxxxxxxxxxxxx>,
> Theodore Ts'o <tytso@xxxxxxx>, linux-fsdevel@xxxxxxxxxxxxxxx,
> xfs@xxxxxxxxxxx
> Subject: Re: [PATCH 5/6 v2] ext4: Introduce FALLOC_FL_ZERO_RANGE flag for
> fallocate
>
> On Wed, Feb 26, 2014 at 1:00 AM, jon ernst <jonernst07@xxxxxxxxx> wrote:
> > On Tue, Feb 25, 2014 at 2:14 PM, Lukas Czerner <lczerner@xxxxxxxxxx> wrote:
> >> Introduce new FALLOC_FL_ZERO_RANGE flag for fallocate. This has the same
> >> functionality as xfs ioctl XFS_IOC_ZERO_RANGE.
> >>
> >> It can be used to convert a range of file to zeros preferably without
> >> issuing data IO. Blocks should be preallocated for the regions that span
> >> holes in the file, and the entire range is preferable converted to
> >> unwritten extents
> >>
> >> This can be also used to preallocate blocks past EOF in the same way as
> >> with fallocate. Flag FALLOC_FL_KEEP_SIZE which should cause the inode
> >> size to remain the same.
> >>
> >> Also add appropriate tracepoints.
> >>
> >> Signed-off-by: Lukas Czerner <lczerner@xxxxxxxxxx>
> >> ---
> >> fs/ext4/ext4.h | 2 +
> >> fs/ext4/extents.c | 270 +++++++++++++++++++++++++++++++++++++++++---
> >> fs/ext4/inode.c | 17 ++-
> >> include/trace/events/ext4.h | 64 +++++------
>
> >> static int
> >> +ext4_ext_convert_initialized_extent(handle_t *handle, struct inode *inode,
> >> + struct ext4_map_blocks *map,
> >> + struct ext4_ext_path *path, int flags,
> >> + unsigned int allocated, ext4_fsblk_t newblock)
> >> +{
> >> + int ret = 0;
> >> + int err = 0;
> >> +
> >> + /*
> >> + * Make sure that the extent is no bigger than we support with
> >> + * uninitialized extent
> >> + */
> >> + if (map->m_len > EXT_UNINIT_MAX_LEN)
> >> + map->m_len = EXT_UNINIT_MAX_LEN / 2;
> >
> Pardon my possible dumb question. Why do you use
> "EXT_UNINIT_MAX_LEN/ 2;" here instead of "EXT_UNINIT_MAX_LEN"
> I don't see the reason why we can't use EXT_UNINIT_MAX_LEN here.
>
>
> (resend, Ping on this question, thank you!)
Wow, that's an early ping :) I am sorry to disappoint you, my answer
is not going to be that exciting :)
Yes, we can just use EXT_UNINIT_MAX_LEN here. But
EXT_UNINIT_MAX_LEN/2 would make it much more evenly spread out.
I do not think there is any real world advantage to this and the
behaviour should be the same in both cases.
Thanks!
-Lukas
>
> Thanks!
> Jon
>
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