Commit 38515c73 authored by Weijie Yang's avatar Weijie Yang Committed by Linus Torvalds

zram: correct offset usage in zram_bio_discard

We want to skip the physical block(PAGE_SIZE) which is partially covered
by the discard bio, so we check the remaining size and subtract it if
there is a need to goto the next physical block.

The current offset usage in zram_bio_discard is incorrect, it will cause
its upper filesystem breakdown.  Consider the following scenario:

On some architecture or config, PAGE_SIZE is 64K for example, filesystem
is set up on zram disk without PAGE_SIZE aligned, a discard bio leads to a
offset = 4K and size=72K, normally, it should not really discard any
physical block as it partially cover two physical blocks.  However, with
the current offset usage, it will discard the second physical block and
free its memory, which will cause filesystem breakdown.

This patch corrects the offset usage in zram_bio_discard.
Signed-off-by: default avatarWeijie Yang <>
Cc: Minchan Kim <>
Cc: Nitin Gupta <>
Acked-by: default avatarJoonsoo Kim <>
Cc: Sergey Senozhatsky <>
Cc: Bob Liu <>
Cc: <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 2a7a0e0f
......@@ -572,10 +572,10 @@ static void zram_bio_discard(struct zram *zram, u32 index,
* skipping this logical block is appropriate here.
if (offset) {
if (n < offset)
if (n <= (PAGE_SIZE - offset))
n -= offset;
n -= (PAGE_SIZE - offset);
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