[PATCH] loop 1/9 file use highmem

[Hugh Dickins]

Here's the first of nine small patches to the loop driver,
mostly to reduce its pressure on zone normal when there's highmem.

I don't pretend these fix every loop hang I see and you not,
nor have I completed reinvestigating those against latest kernel.
These patches just remove what I hope we'll agree is silliness,
setting a base for further work.

(Some could conceivably make some loads worse: making better use of
highmem for data could in theory expose kmap deadlocks, I've never seen,
or permit so much more data in transit that mempool exhaustion wins:
if so, we fix those issues, rather than depending on mistakes.)

Based on 2.5.70-mm7.  Aggregate diffstat is:

 drivers/block/loop.c |   71 +++++++++++++++++++++++++++------------------
 fs/bio.c             |   79 ---------------------------------------------------
 include/linux/bio.h  |    1 
 include/linux/loop.h |    1 
 4 files changed, 43 insertions(+), 109 deletions(-)

loop 1/9 file use highmem

When loop restricts underlying file's allocation mask to avoid
deadlock, it unintentionally masks out its highmem capability,
making failures at the underlying level much more likely.

--- 2.5.70-mm7/drivers/block/loop.c	Mon Jun  9 10:14:55 2003
+++ loop1/drivers/block/loop.c	Mon Jun  9 10:29:01 2003
@@ -714,7 +714,7 @@
 		goto out_putf;
 	}
 	lo->old_gfp_mask = inode->i_mapping->gfp_mask;
-	inode->i_mapping->gfp_mask = GFP_NOIO;
+	inode->i_mapping->gfp_mask &= ~(__GFP_IO|__GFP_FS);
 
 	set_blocksize(bdev, lo_blocksize);