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Patch "dm bufio: make the parameter "retain_bytes" unsigned long" has been added to the 4.9-stable tree

PATCH [email protected] 1 participant 1 message May 22, 2017

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This is a note to let you know that I've just added the patch titled

dm bufio: make the parameter "retain_bytes" unsigned long

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
dm-bufio-make-the-parameter-retain_bytes-unsigned-long.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From 13840d38016203f0095cd547b90352812d24b787 Mon Sep 17 00:00:00 2001

From: Mikulas Patocka <[email protected]>
Date: Sun, 30 Apr 2017 17:32:28 -0400
Subject: dm bufio: make the parameter "retain_bytes" unsigned long

From: Mikulas Patocka <[email protected]>

commit 13840d38016203f0095cd547b90352812d24b787 upstream.

Change the type of the parameter "retain_bytes" from unsigned to unsigned long, so that on 64-bit machines the user can set more than 4GiB of data to be retained.

Also, change the type of the variable "count" in the function "__evict_old_buffers" to unsigned long. The assignment "count = c->n_buffers[LIST_CLEAN] + c->n_buffers[LIST_DIRTY];" could result in unsigned long to unsigned overflow and that could result in buffers not being freed when they should.

While at it, avoid division in get_retain_buffers(). Division is slow, we can change it to shift because we have precalculated the log2 of block size.

Signed-off-by Mikulas Patocka <[email protected]>
Signed-off-by Mike Snitzer <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 drivers/md/dm-bufio.c |   16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)
drivers/md/dm-bufio.c +8 -8
@@ -215,7 +215,7 @@ static DEFINE_SPINLOCK(param_spinlock);
  * Buffers are freed after this timeout
  */
 static unsigned dm_bufio_max_age = DM_BUFIO_DEFAULT_AGE_SECS;
-static unsigned dm_bufio_retain_bytes = DM_BUFIO_DEFAULT_RETAIN_BYTES;
+static unsigned long dm_bufio_retain_bytes = DM_BUFIO_DEFAULT_RETAIN_BYTES;
 
 static unsigned long dm_bufio_peak_allocated;
 static unsigned long dm_bufio_allocated_kmem_cache;

@@ -1541,10 +1541,10 @@ static bool __try_evict_buffer(struct dm
 	return true;
 }
 
-static unsigned get_retain_buffers(struct dm_bufio_client *c)
+static unsigned long get_retain_buffers(struct dm_bufio_client *c)
 {
-        unsigned retain_bytes = ACCESS_ONCE(dm_bufio_retain_bytes);
-        return retain_bytes / c->block_size;
+        unsigned long retain_bytes = ACCESS_ONCE(dm_bufio_retain_bytes);
+        return retain_bytes >> (c->sectors_per_block_bits + SECTOR_SHIFT);
 }
 
 static unsigned long __scan(struct dm_bufio_client *c, unsigned long nr_to_scan,

@@ -1554,7 +1554,7 @@ static unsigned long __scan(struct dm_bu
 	struct dm_buffer *b, *tmp;
 	unsigned long freed = 0;
 	unsigned long count = nr_to_scan;
-	unsigned retain_target = get_retain_buffers(c);
+	unsigned long retain_target = get_retain_buffers(c);
 
 	for (l = 0; l < LIST_SIZE; l++) {
 		list_for_each_entry_safe_reverse(b, tmp, &c->lru[l], lru_list) {

@@ -1780,8 +1780,8 @@ static bool older_than(struct dm_buffer
 static void __evict_old_buffers(struct dm_bufio_client *c, unsigned long age_hz)
 {
 	struct dm_buffer *b, *tmp;
-	unsigned retain_target = get_retain_buffers(c);
-	unsigned count;
+	unsigned long retain_target = get_retain_buffers(c);
+	unsigned long count;
 	LIST_HEAD(write_list);
 
 	dm_bufio_lock(c);

@@ -1941,7 +1941,7 @@ MODULE_PARM_DESC(max_cache_size_bytes, "
 module_param_named(max_age_seconds, dm_bufio_max_age, uint, S_IRUGO | S_IWUSR);
 MODULE_PARM_DESC(max_age_seconds, "Max age of a buffer in seconds");
 
-module_param_named(retain_bytes, dm_bufio_retain_bytes, uint, S_IRUGO | S_IWUSR);
+module_param_named(retain_bytes, dm_bufio_retain_bytes, ulong, S_IRUGO | S_IWUSR);
 MODULE_PARM_DESC(retain_bytes, "Try to keep at least this many bytes cached in memory");
 
 module_param_named(peak_allocated_bytes, dm_bufio_peak_allocated, ulong, S_IRUGO | S_IWUSR);

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/dm-bufio-avoid-a-possible-abba-deadlock.patch queue-4.9/dm-cache-metadata-fail-operations-if-fail_io-mode-has-been-established.patch queue-4.9/dm-raid-select-the-kconfig-option-config_md_raid0.patch queue-4.9/dm-bufio-make-the-parameter-retain_bytes-unsigned-long.patch queue-4.9/dm-bufio-check-new-buffer-allocation-watermark-every-30-seconds.patch