Re: [Qemu-trivial] [Nbd] [Qemu-devel] [PATCH] nbd: fix trim/discard commands with a length bigger than NBD_MAX_BUFFER_SIZE

[Alex Bligh]

On 10 May 2016, at 16:46, Eric Blake <address@hidden> wrote:

> Does anyone have an easy way to cause the kernel to request a trim
> operation that large on a > 4G export?  I'm not familiar enough with
> EXT4 operation to know what file system operations you can run to
> ultimately indirectly create a file system trim operation that large.
> But maybe there is something simpler - does the kernel let you use the
> fallocate(2) syscall operation with FALLOC_FL_PUNCH_HOLE or
> FALLOC_FL_ZERO_RANGE on an fd backed by an NBD device?

Not tried it, but fallocate(1) with -p ?

http://man7.org/linux/man-pages/man1/fallocate.1.html

As it takes length and offset in TB, PB, EB, ZB and YB, it
seems to be 64 bit aware :-)

--
Alex Bligh

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