fs/ntfs/aops.c: don't disable interrupts during kmap_atomic()

ntfs_end_buffer_async_read() disables interrupts around kmap_atomic().
This is a leftover from the old kmap_atomic() implementation which
relied on fixed mapping slots, so the caller had to make sure that the
same slot could not be reused from an interrupting context.

kmap_atomic() was changed to dynamic slots long ago and commit
1ec9c5ddc1 ("include/linux/highmem.h: remove the second argument of
k[un]map_atomic()") removed the slot assignements, but the callers were
not checked for now redundant interrupt disabling.

Remove the conditional interrupt disable.

Link: http://lkml.kernel.org/r/20180611144913.gln5mklhqcrfsoom@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Anton Altaparmakov <anton@tuxera.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/ntfs/aops.c

@@ -93,13 +93,11 @@ static void ntfs_end_buffer_async_read(struct buffer_head *bh, int uptodate)
 			ofs = 0;
 			if (file_ofs < init_size)
 				ofs = init_size - file_ofs;
-			local_irq_save(flags);
 			kaddr = kmap_atomic(page);
 			memset(kaddr + bh_offset(bh) + ofs, 0,
 					bh->b_size - ofs);
 			flush_dcache_page(page);
 			kunmap_atomic(kaddr);
-			local_irq_restore(flags);
 		}
 	} else {
 		clear_buffer_uptodate(bh);
@@ -146,13 +144,11 @@ static void ntfs_end_buffer_async_read(struct buffer_head *bh, int uptodate)
 		recs = PAGE_SIZE / rec_size;
 		/* Should have been verified before we got here... */
 		BUG_ON(!recs);
-		local_irq_save(flags);
 		kaddr = kmap_atomic(page);
 		for (i = 0; i < recs; i++)
 			post_read_mst_fixup((NTFS_RECORD*)(kaddr +
 					i * rec_size), rec_size);
 		kunmap_atomic(kaddr);
-		local_irq_restore(flags);
 		flush_dcache_page(page);
 		if (likely(page_uptodate && !PageError(page)))
 			SetPageUptodate(page);