lib/commands/toolcontext.c   |  2 ++

 lib/config/config_settings.h |  8 ++++++++

 lib/config/defaults.h        |  2 ++

 lib/label/label.c            | 40 ++++++++++++++++++++--------------------

 lib/misc/lvm-globals.c       | 10 ++++++++++

 lib/misc/lvm-globals.h       |  3 +++

 6 files changed, 45 insertions(+), 20 deletions(-)

diff --git a/lib/commands/toolcontext.c b/lib/commands/toolcontext.c

index 4d3f744..95b2317 100644

--- a/lib/commands/toolcontext.c

+++ b/lib/commands/toolcontext.c

@@ -693,6 +693,8 @@ static int _process_config(struct cmd_context *cmd)

 	if (!_init_system_id(cmd))

 		return_0;

+	init_io_memory_size(find_config_tree_int(cmd, global_io_memory_size_CFG, NULL));

+

 	return 1;

 }

diff --git a/lib/config/config_settings.h b/lib/config/config_settings.h

index 2de3fd4..c3e9600 100644

--- a/lib/config/config_settings.h

+++ b/lib/config/config_settings.h

@@ -1138,6 +1138,14 @@ cfg(global_notify_dbus_CFG, "notify_dbus", global_CFG_SECTION, 0, CFG_TYPE_BOOL,

 	"When enabled, an LVM command that changes PVs, changes VG metadata,\n"

 	"or changes the activation state of an LV will send a notification.\n")

+cfg(global_io_memory_size_CFG, "io_memory_size", global_CFG_SECTION, CFG_DEFAULT_COMMENTED, CFG_TYPE_INT, DEFAULT_IO_MEMORY_SIZE_KB, vsn(2, 2, 184), NULL, 0, NULL,

+	"The amount of memory in KiB that LVM allocates to perform disk io.\n"

+	"LVM performance may benefit from more io memory when there are many\n"

+	"disks or VG metadata is large. Increasing this size may be necessary\n"

+	"when a single copy of VG metadata is larger than the current setting.\n"

+	"This value should usually not be decreased from the default; setting\n"

+	"it too low can result in lvm failing to read VGs.\n")

+

 cfg(activation_udev_sync_CFG, "udev_sync", activation_CFG_SECTION, 0, CFG_TYPE_BOOL, DEFAULT_UDEV_SYNC, vsn(2, 2, 51), NULL, 0, NULL,

 	"Use udev notifications to synchronize udev and LVM.\n"

 	"The --nodevsync option overrides this setting.\n"

diff --git a/lib/config/defaults.h b/lib/config/defaults.h

index b3e6c34..690bf56 100644

--- a/lib/config/defaults.h

+++ b/lib/config/defaults.h

@@ -267,4 +267,6 @@

 #define DEFAULT_THIN_POOL_AUTOEXTEND_THRESHOLD 100

 #define DEFAULT_THIN_POOL_AUTOEXTEND_PERCENT 20

+#define DEFAULT_IO_MEMORY_SIZE_KB 4096

+

 #endif				/* _LVM_DEFAULTS_H */

diff --git a/lib/label/label.c b/lib/label/label.c

index 03726d0..4ec7d9b 100644

--- a/lib/label/label.c

+++ b/lib/label/label.c

@@ -772,33 +772,33 @@ out:

 }

 /*

- * How many blocks to set up in bcache?  Is 1024 a good max?

+ * num_devs is the number of devices the caller is going to scan.

+ * When 0 the caller doesn't know, and we use the default cache size.

+ * When non-zero, allocate at least num_devs bcache blocks.

+ * num_devs doesn't really tell us how many bcache blocks we'll use

+ * because it includes lvm devs and non-lvm devs, and each lvm dev

+ * will often use a number of bcache blocks.

  *

- * Currently, we tell bcache to set up N blocks where N

- * is the number of devices that are going to be scanned.

- * Reasons why this number may not be be a good choice:

- *

- * - there may be a lot of non-lvm devices, which

- *   would make this number larger than necessary

- *

- * - each lvm device may use more than one cache

- *   block if the metadata is large enough or it

- *   uses more than one metadata area, which

- *   would make this number smaller than it

- *   should be for the best performance.

- *

- * This is even more tricky to estimate when lvmetad

- * is used, because it's hard to predict how many

- * devs might need to be scanned when using lvmetad.

- * This currently just sets up bcache with MIN blocks.

+ * We don't know ahead of time if we will find some VG metadata 

+ * that is larger than the total size of the bcache, which would

+ * prevent us from reading/writing the VG since we do not dynamically

+ * increase the bcache size when we find it's too small.  In these

+ * cases the user would need to set io_memory_size to be larger

+ * than the max VG metadata size (lvm does not impose any limit on

+ * the metadata size.)

  */

-#define MIN_BCACHE_BLOCKS 32

+#define MIN_BCACHE_BLOCKS 32    /* 4MB, currently matches DEFAULT_IO_MEMORY_SIZE_KB */

 #define MAX_BCACHE_BLOCKS 1024

-static int _setup_bcache(int cache_blocks)

+static int _setup_bcache(int num_devs)

 {

 	struct io_engine *ioe = NULL;

+	int iomem_kb = io_memory_size();

+	int block_size_kb = (BCACHE_BLOCK_SIZE_IN_SECTORS * 512) / 1024;

+	int cache_blocks;

+

+	cache_blocks = iomem_kb / block_size_kb;

 	if (cache_blocks < MIN_BCACHE_BLOCKS)

 		cache_blocks = MIN_BCACHE_BLOCKS;

diff --git a/lib/misc/lvm-globals.c b/lib/misc/lvm-globals.c

index 82c5706..3bd5cac 100644

--- a/lib/misc/lvm-globals.c

+++ b/lib/misc/lvm-globals.c

@@ -54,6 +54,7 @@ static char _sysfs_dir_path[PATH_MAX] = "";

 static int _dev_disable_after_error_count = DEFAULT_DISABLE_AFTER_ERROR_COUNT;

 static uint64_t _pv_min_size = (DEFAULT_PV_MIN_SIZE_KB * 1024L >> SECTOR_SHIFT);

 static const char *_unknown_device_name = DEFAULT_UNKNOWN_DEVICE_NAME;

+static int _io_memory_size_kb = DEFAULT_IO_MEMORY_SIZE_KB;

 void init_verbose(int level)

 {

@@ -387,3 +388,12 @@ void init_unknown_device_name(const char *name)

 	_unknown_device_name = name;

 }

+int io_memory_size(void)

+{

+	return _io_memory_size_kb;

+}

+

+void init_io_memory_size(int val)

+{

+	_io_memory_size_kb = val;

+}

diff --git a/lib/misc/lvm-globals.h b/lib/misc/lvm-globals.h

index f985cfa..3007cc5 100644

--- a/lib/misc/lvm-globals.h

+++ b/lib/misc/lvm-globals.h

@@ -53,6 +53,7 @@ void init_pv_min_size(uint64_t sectors);

 void init_activation_checks(int checks);

 void init_retry_deactivation(int retry);

 void init_unknown_device_name(const char *name);

+void init_io_memory_size(int val);

 void set_cmd_name(const char *cmd_name);

 const char *get_cmd_name(void);

@@ -86,6 +87,7 @@ uint64_t pv_min_size(void);

 int activation_checks(void);

 int retry_deactivation(void);

 const char *unknown_device_name(void);

+int io_memory_size(void);

 #define DMEVENTD_MONITOR_IGNORE -1

 int dmeventd_monitor_mode(void);

@@ -93,4 +95,5 @@ int dmeventd_monitor_mode(void);

 #define NO_DEV_ERROR_COUNT_LIMIT 0

 int dev_disable_after_error_count(void);

+

 #endif