vmsplice: relax alignement requirements for SPLICE_F_GIFT
vmsplice: relax alignement requirements for SPLICE_F_GIFT

It seems there is no fundamental reason to limit vmsplice()
SPLICE_F_GIFT to page aligned chunks.

All helpers are prepared to cope with offsets in page.

This limitation makes vmsplice() API very impractical in the zero-copy
land.

Signed-off-by: Eric Dumazet <a0baddf32b28d2f9429941ed4af2fe636e210591@gmail.com>
Cc: Tom Herbert <0786393240831fc3b5d6ed63658cfb1f3b1e6c40@google.com>
Cc: Jens Axboe <cd8c6775e60d6f67a6984377324e5290df3d5358@kernel.dk>
Cc: Andrew Morton <5c1e68b099950c134891f0b6e179498a8ebe9cf9@linux-foundation.org>
Cc: David Miller <fe08d3c717adf2ae63592e4c9aec6e3e404d8e3e@davemloft.net>
Cc: Al Viro <de609eb4d5d70b1d38ec6642adbfc33a2781f63c@zeniv.linux.org.uk>
Cc: Hugh Dickins <d3abdf3e2800e6cb849f11b81e6eb50b34d96431@google.com>
Cc: Changli Gao <e0c990ad75746f704921cca52caa8fdda39c56b7@gmail.com>
Cc: Miklos Szeredi <84cd5483a2f9acd1c37251cba7c2908448f221b8@suse.cz>
Signed-off-by: Jens Axboe <cd8c6775e60d6f67a6984377324e5290df3d5358@kernel.dk>

TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas