[to-be-updated] zram-handle-multiple-pages-attached-bios-bvec.patch removed from -mm tree

[to-be-updated] zram-handle-multiple-pages-attached-bios-bvec.patch removed from -mm tree

[akpm]

The patch titled
     Subject: zram: handle multiple pages attached to bio's bvec
has been removed from the -mm tree.  Its filename was
     zram-handle-multiple-pages-attached-bios-bvec.patch

This patch was dropped because an updated version will be merged

------------------------------------------------------
From: Minchan Kim <minchan@kernel.org>
Subject: zram: handle multiple pages attached to bio's bvec

Johannes Thumshirn reported system goes the panic when using NVMe over
Fabrics loopback target with zram.

The reason is zram expects each bvec in bio contains a single page but
nvme can attach a huge bulk of pages attached to the bio's bvec so that
zram's index arithmetic could be wrong so that out-of-bound access makes
panic.

It was solved by limiting max_sectors with SECTORS_PER_PAGE in
0bc315381fe9 ("zram: set physical queue limits to avoid array out of
bounds accesses") but that makes zram slow because a bio should split
with each pages.  So this patch makes zram aware of multiple pages in a
bvec so it can solve the panic without causing any performance
regression.

Link: http://lkml.kernel.org/r/1491196653-7388-2-git-send-email-minchan@kernel.org
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Minchan Kim <minchan@kernel.org>
Reported-by: Johannes Thumshirn <jthumshirn@suse.de>
Tested-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Mika Penttil <mika.penttila@nextfour.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 drivers/block/zram/zram_drv.c |   39 ++++++++------------------------
 1 file changed, 10 insertions(+), 29 deletions(-)

diff -puN drivers/block/zram/zram_drv.c~zram-handle-multiple-pages-attached-bios-bvec drivers/block/zram/zram_drv.c
--- a/drivers/block/zram/zram_drv.c~zram-handle-multiple-pages-attached-bios-bvec
+++ a/drivers/block/zram/zram_drv.c
@@ -137,8 +137,7 @@ static inline bool valid_io_request(stru
 
 static void update_position(u32 *index, int *offset, struct bio_vec *bvec)
 {
-	if (*offset + bvec->bv_len >= PAGE_SIZE)
-		(*index)++;
+	*index  += (*offset + bvec->bv_len) / PAGE_SIZE;
 	*offset = (*offset + bvec->bv_len) % PAGE_SIZE;
 }
 
@@ -838,34 +837,20 @@ static void __zram_make_request(struct z
 	}
 
 	bio_for_each_segment(bvec, bio, iter) {
-		int max_transfer_size = PAGE_SIZE - offset;
-
-		if (bvec.bv_len > max_transfer_size) {
-			/*
-			 * zram_bvec_rw() can only make operation on a single
-			 * zram page. Split the bio vector.
-			 */
-			struct bio_vec bv;
-
-			bv.bv_page = bvec.bv_page;
-			bv.bv_len = max_transfer_size;
-			bv.bv_offset = bvec.bv_offset;
+		struct bio_vec bv = bvec;
+		unsigned int remained = bvec.bv_len;
 
+		do {
+			bv.bv_len = min_t(unsigned int, PAGE_SIZE, remained);
 			if (zram_bvec_rw(zram, &bv, index, offset,
-					 op_is_write(bio_op(bio))) < 0)
+					op_is_write(bio_op(bio))) < 0)
 				goto out;
 
-			bv.bv_len = bvec.bv_len - max_transfer_size;
-			bv.bv_offset += max_transfer_size;
-			if (zram_bvec_rw(zram, &bv, index + 1, 0,
-					 op_is_write(bio_op(bio))) < 0)
-				goto out;
-		} else
-			if (zram_bvec_rw(zram, &bvec, index, offset,
-					 op_is_write(bio_op(bio))) < 0)
-				goto out;
+			bv.bv_offset += bv.bv_len;
+			remained -= bv.bv_len;
 
-		update_position(&index, &offset, &bvec);
+			update_position(&index, &offset, &bv);
+		} while (remained);
 	}
 
 	bio_endio(bio);
@@ -882,8 +867,6 @@ static blk_qc_t zram_make_request(struct
 {
 	struct zram *zram = queue->queuedata;
 
-	blk_queue_split(queue, &bio, queue->bio_split);
-
 	if (!valid_io_request(zram, bio->bi_iter.bi_sector,
 					bio->bi_iter.bi_size)) {
 		atomic64_inc(&zram->stats.invalid_io);
@@ -1191,8 +1174,6 @@ static int zram_add(void)
 	blk_queue_io_min(zram->disk->queue, PAGE_SIZE);
 	blk_queue_io_opt(zram->disk->queue, PAGE_SIZE);
 	zram->disk->queue->limits.discard_granularity = PAGE_SIZE;
-	zram->disk->queue->limits.max_sectors = SECTORS_PER_PAGE;
-	zram->disk->queue->limits.chunk_sectors = 0;
 	blk_queue_max_discard_sectors(zram->disk->queue, UINT_MAX);
 	/*
 	 * zram_bio_discard() will clear all logical blocks if logical block
_

Patches currently in -mm which might be from minchan@kernel.org are

mm-reclaim-madv_free-pages-fix.patch
mm-fix-lazyfree-bug-on-check-in-try_to_unmap_one.patch
mm-fix-lazyfree-bug-on-check-in-try_to_unmap_one-fix.patch
mm-do-not-use-double-negation-for-testing-page-flags.patch
mm-remove-unncessary-ret-in-page_referenced.patch
mm-remove-swap_dirty-in-ttu.patch
mm-remove-swap_mlock-check-for-swap_success-in-ttu.patch
mm-make-the-try_to_munlock-void-function.patch
mm-remove-swap_mlock-in-ttu.patch
mm-remove-swap_again-in-ttu.patch
mm-make-ttus-return-boolean.patch
mm-make-rmap_walk-void-function.patch
mm-make-rmap_one-boolean-function.patch
mm-remove-swap_.patch
mm-remove-swap_-fix.patch
zram-partial-io-refactoring.patch
zram-use-zram_slot_lock-instead-of-raw-bit_spin_lock-op.patch
zram-remove-zram_meta-structure.patch
zram-introduce-zram-data-accessor.patch