mm: implement find_get_pages_range_tag()

mm: implement find_get_pages_range_tag()

Patch series "Ranged pagevec tagged lookup", v3.

In this series I provide a ranged variant of pagevec_lookup_tag() and
use it in places where it makes sense.  This series removes some common
code and it also has a potential for speeding up some operations
similarly as for pagevec_lookup_range() (but for now I can think of only
artificial cases where this happens).

This patch (of 16):

Implement a variant of find_get_pages_tag() that stops iterating at
given index.  Lots of users of this function (through pagevec_lookup())
actually want a range lookup and all of them are currently open-coding
this.

Also create corresponding pagevec_lookup_range_tag() function.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Jan Kara <[email protected]>
Reviewed-by: Daniel Jordan <[email protected]>
Cc: Bob Peterson <[email protected]>
Cc: Chao Yu <[email protected]>
Cc: David Howells <[email protected]>
Cc: David Sterba <[email protected]>
Cc: Ilya Dryomov <[email protected]>
Cc: Jaegeuk Kim <[email protected]>
Cc: Ryusuke Konishi <[email protected]>
Cc: Steve French <[email protected]>
Cc: "Theodore Ts'o" <[email protected]>
Cc: "Yan, Zheng" <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>