+ zram-drop-num_active_comps.patch added to mm-new branch

+ zram-drop-num_active_comps.patch added to mm-new branch

[Andrew Morton]

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The patch titled
     Subject: zram: drop ->num_active_comps
has been added to the -mm mm-new branch.  Its filename is
     zram-drop-num_active_comps.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/zram-drop-num_active_comps.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

The mm-new branch of mm.git is not included in linux-next

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------------------------------------------------------
From: Sergey Senozhatsky <senozhatsky@chromium.org>
Subject: zram: drop ->num_active_comps
Date: Fri, 27 Feb 2026 17:21:08 +0900

It's not entirely correct to use ->num_active_comps for max-prio limit, as
->num_active_comps just tells the number of configured algorithms, not the
max configured priority.  For instance, in the following theoretical
example:

    [lz4] [nil] [nil] [deflate]

->num_active_comps is 2, while the actual max-prio is 3.

Drop ->num_active_comps and use ZRAM_MAX_COMPS instead.

Link: https://lkml.kernel.org/r/eb7cd3ca578320be9aff13e71298fc36e110af41.1772180459.git.senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Suggested-by: Minchan Kim <minchan@kernel.org>
Cc: Brian Geffon <bgeffon@google.com>
Cc: "Christoph Böhmwalder" <christoph.boehmwalder@linbit.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Lars Ellenberg <lars.ellenberg@linbit.com>
Cc: Philipp Reisner <philipp.reisner@linbit.com>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 drivers/block/zram/zram_drv.c |   29 ++++++++++++++++-------------
 drivers/block/zram/zram_drv.h |    1 -
 2 files changed, 16 insertions(+), 14 deletions(-)

--- a/drivers/block/zram/zram_drv.c~zram-drop-num_active_comps
+++ a/drivers/block/zram/zram_drv.c
@@ -2371,6 +2371,18 @@ next:
 	return 0;
 }
 
+static bool highest_priority_algorithm(struct zram *zram, u32 prio)
+{
+	u32 p;
+
+	for (p = prio + 1; p < ZRAM_MAX_COMPS; p++) {
+		if (zram->comp_algs[p])
+			return false;
+	}
+
+	return true;
+}
+
 /*
  * This function will decompress (unless it's ZRAM_HUGE) the page and then
  * attempt to compress it using provided compression algorithm priority
@@ -2478,12 +2490,11 @@ static int recompress_slot(struct zram *
 		 * Secondary algorithms failed to re-compress the page
 		 * in a way that would save memory.
 		 *
-		 * Mark the object incompressible if the max-priority
-		 * algorithm couldn't re-compress it.
+		 * Mark the object incompressible if the max-priority (the
+		 * last configured one) algorithm couldn't re-compress it.
 		 */
-		if (prio < zram->num_active_comps)
-			return 0;
-		set_slot_flag(zram, index, ZRAM_INCOMPRESSIBLE);
+		if (highest_priority_algorithm(zram, prio))
+			set_slot_flag(zram, index, ZRAM_INCOMPRESSIBLE);
 		return 0;
 	}
 
@@ -2615,12 +2626,6 @@ static ssize_t recompress_store(struct d
 		}
 	}
 
-	prio_max = min(prio_max, (u32)zram->num_active_comps);
-	if (prio >= prio_max) {
-		ret = -EINVAL;
-		goto out;
-	}
-
 	if (prio < ZRAM_SECONDARY_COMP || prio >= ZRAM_MAX_COMPS) {
 		ret = -EINVAL;
 		goto out;
@@ -2833,7 +2838,6 @@ static void zram_destroy_comps(struct zr
 		if (!comp)
 			continue;
 		zcomp_destroy(comp);
-		zram->num_active_comps--;
 	}
 
 	for (prio = ZRAM_PRIMARY_COMP; prio < ZRAM_MAX_COMPS; prio++)
@@ -2898,7 +2902,6 @@ static ssize_t disksize_store(struct dev
 		}
 
 		zram->comps[prio] = comp;
-		zram->num_active_comps++;
 	}
 	zram->disksize = disksize;
 	set_capacity_and_notify(zram->disk, zram->disksize >> SECTOR_SHIFT);
--- a/drivers/block/zram/zram_drv.h~zram-drop-num_active_comps
+++ a/drivers/block/zram/zram_drv.h
@@ -125,7 +125,6 @@ struct zram {
 	 */
 	u64 disksize;	/* bytes */
 	const char *comp_algs[ZRAM_MAX_COMPS];
-	s8 num_active_comps;
 	/*
 	 * zram is claimed so open request will be failed
 	 */
_

Patches currently in -mm which might be from senozhatsky@chromium.org are

zram-rename-writeback_compressed-device-attr.patch
zram-do-not-autocorrect-bad-recompression-parameters.patch
zram-drop-num_active_comps.patch
zram-recompression-priority-param-should-override-algo.patch
zram-update-recompression-documentation.patch
zram-remove-chained-recompression.patch