--- /dev/null
+From 37887783b3fef877bf34b8992c9199864da4afcb Mon Sep 17 00:00:00 2001
+From: Jiri Slaby <jslaby@suse.cz>
+Date: Wed, 10 Aug 2022 09:06:09 +0200
+Subject: Revert "zram: remove double compression logic"
+
+From: Jiri Slaby <jslaby@suse.cz>
+
+commit 37887783b3fef877bf34b8992c9199864da4afcb upstream.
+
+This reverts commit e7be8d1dd983156b ("zram: remove double compression
+logic") as it causes zram failures. It does not revert cleanly, PTR_ERR
+handling was introduced in the meantime. This is handled by appropriate
+IS_ERR.
+
+When under memory pressure, zs_malloc() can fail. Before the above
+commit, the allocation was retried with direct reclaim enabled (GFP_NOIO).
+After the commit, it is not -- only __GFP_KSWAPD_RECLAIM is tried.
+
+So when the failure occurs under memory pressure, the overlaying
+filesystem such as ext2 (mounted by ext4 module in this case) can emit
+failures, making the (file)system unusable:
+ EXT4-fs warning (device zram0): ext4_end_bio:343: I/O error 10 writing to inode 16386 starting block 159744)
+ Buffer I/O error on device zram0, logical block 159744
+
+With direct reclaim, memory is really reclaimed and allocation succeeds,
+eventually. In the worst case, the oom killer is invoked, which is proper
+outcome if user sets up zram too large (in comparison to available RAM).
+
+This very diff doesn't apply to 5.19 (stable) cleanly (see PTR_ERR note
+above). Use revert of e7be8d1dd983 directly.
+
+Link: https://bugzilla.suse.com/show_bug.cgi?id=1202203
+Link: https://lkml.kernel.org/r/20220810070609.14402-1-jslaby@suse.cz
+Fixes: e7be8d1dd983 ("zram: remove double compression logic")
+Signed-off-by: Jiri Slaby <jslaby@suse.cz>
+Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
+Cc: Minchan Kim <minchan@kernel.org>
+Cc: Nitin Gupta <ngupta@vflare.org>
+Cc: Alexey Romanov <avromanov@sberdevices.ru>
+Cc: Dmitry Rokosov <ddrokosov@sberdevices.ru>
+Cc: Lukas Czerner <lczerner@redhat.com>
+Cc: <stable@vger.kernel.org> [5.19]
+Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ drivers/block/zram/zram_drv.c | 42 ++++++++++++++++++++++++++++++++----------
+ drivers/block/zram/zram_drv.h | 1 +
+ 2 files changed, 33 insertions(+), 10 deletions(-)
+
+--- a/drivers/block/zram/zram_drv.c
++++ b/drivers/block/zram/zram_drv.c
+@@ -1144,14 +1144,15 @@ static ssize_t bd_stat_show(struct devic
+ static ssize_t debug_stat_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+ {
+- int version = 2;
++ int version = 1;
+ struct zram *zram = dev_to_zram(dev);
+ ssize_t ret;
+
+ down_read(&zram->init_lock);
+ ret = scnprintf(buf, PAGE_SIZE,
+- "version: %d\n%8llu\n",
++ "version: %d\n%8llu %8llu\n",
+ version,
++ (u64)atomic64_read(&zram->stats.writestall),
+ (u64)atomic64_read(&zram->stats.miss_free));
+ up_read(&zram->init_lock);
+
+@@ -1367,6 +1368,7 @@ static int __zram_bvec_write(struct zram
+ }
+ kunmap_atomic(mem);
+
++compress_again:
+ zstrm = zcomp_stream_get(zram->comp);
+ src = kmap_atomic(page);
+ ret = zcomp_compress(zstrm, src, &comp_len);
+@@ -1375,20 +1377,39 @@ static int __zram_bvec_write(struct zram
+ if (unlikely(ret)) {
+ zcomp_stream_put(zram->comp);
+ pr_err("Compression failed! err=%d\n", ret);
++ zs_free(zram->mem_pool, handle);
+ return ret;
+ }
+
+ if (comp_len >= huge_class_size)
+ comp_len = PAGE_SIZE;
+-
+- handle = zs_malloc(zram->mem_pool, comp_len,
+- __GFP_KSWAPD_RECLAIM |
+- __GFP_NOWARN |
+- __GFP_HIGHMEM |
+- __GFP_MOVABLE);
+-
+- if (unlikely(!handle)) {
++ /*
++ * handle allocation has 2 paths:
++ * a) fast path is executed with preemption disabled (for
++ * per-cpu streams) and has __GFP_DIRECT_RECLAIM bit clear,
++ * since we can't sleep;
++ * b) slow path enables preemption and attempts to allocate
++ * the page with __GFP_DIRECT_RECLAIM bit set. we have to
++ * put per-cpu compression stream and, thus, to re-do
++ * the compression once handle is allocated.
++ *
++ * if we have a 'non-null' handle here then we are coming
++ * from the slow path and handle has already been allocated.
++ */
++ if (!handle)
++ handle = zs_malloc(zram->mem_pool, comp_len,
++ __GFP_KSWAPD_RECLAIM |
++ __GFP_NOWARN |
++ __GFP_HIGHMEM |
++ __GFP_MOVABLE);
++ if (!handle) {
+ zcomp_stream_put(zram->comp);
++ atomic64_inc(&zram->stats.writestall);
++ handle = zs_malloc(zram->mem_pool, comp_len,
++ GFP_NOIO | __GFP_HIGHMEM |
++ __GFP_MOVABLE);
++ if (handle)
++ goto compress_again;
+ return -ENOMEM;
+ }
+
+@@ -1946,6 +1967,7 @@ static int zram_add(void)
+ if (ZRAM_LOGICAL_BLOCK_SIZE == PAGE_SIZE)
+ blk_queue_max_write_zeroes_sectors(zram->disk->queue, UINT_MAX);
+
++ blk_queue_flag_set(QUEUE_FLAG_STABLE_WRITES, zram->disk->queue);
+ ret = device_add_disk(NULL, zram->disk, zram_disk_groups);
+ if (ret)
+ goto out_cleanup_disk;
+--- a/drivers/block/zram/zram_drv.h
++++ b/drivers/block/zram/zram_drv.h
+@@ -81,6 +81,7 @@ struct zram_stats {
+ atomic64_t huge_pages_since; /* no. of huge pages since zram set up */
+ atomic64_t pages_stored; /* no. of pages currently stored */
+ atomic_long_t max_used_pages; /* no. of maximum pages stored */
++ atomic64_t writestall; /* no. of write slow paths */
+ atomic64_t miss_free; /* no. of missed free */
+ #ifdef CONFIG_ZRAM_WRITEBACK
+ atomic64_t bd_count; /* no. of pages in backing device */
projects / thirdparty / kernel / stable-queue.git / commitdiff
