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authorJames Morris <jmorris@namei.org>2009-05-22 18:40:59 +1000
committerJames Morris <jmorris@namei.org>2009-05-22 18:40:59 +1000
commit2c9e703c618106f5383226fbb1f526cb11034f8a (patch)
tree87d7548001ea82f655fede0640466fc16aabcdf7 /Documentation
parent6470c077cae12227318f40f3e6d756caadcce4b0 (diff)
parent5805977e63a36ad56594a623f3bd2bebcb7db233 (diff)
downloadlinux-2c9e703c618106f5383226fbb1f526cb11034f8a.tar.bz2
Merge branch 'master' into next
Conflicts: fs/exec.c Removed IMA changes (the IMA checks are now performed via may_open()). Signed-off-by: James Morris <jmorris@namei.org>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/ABI/testing/sysfs-kernel-slab479
-rw-r--r--Documentation/DocBook/kgdb.tmpl2
-rw-r--r--Documentation/networking/ip-sysctl.txt15
-rw-r--r--Documentation/sysctl/vm.txt28
-rw-r--r--Documentation/sysfs-rules.txt2
5 files changed, 493 insertions, 33 deletions
diff --git a/Documentation/ABI/testing/sysfs-kernel-slab b/Documentation/ABI/testing/sysfs-kernel-slab
new file mode 100644
index 000000000000..6dcf75e594fb
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-kernel-slab
@@ -0,0 +1,479 @@
+What: /sys/kernel/slab
+Date: May 2007
+KernelVersion: 2.6.22
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The /sys/kernel/slab directory contains a snapshot of the
+ internal state of the SLUB allocator for each cache. Certain
+ files may be modified to change the behavior of the cache (and
+ any cache it aliases, if any).
+Users: kernel memory tuning tools
+
+What: /sys/kernel/slab/cache/aliases
+Date: May 2007
+KernelVersion: 2.6.22
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The aliases file is read-only and specifies how many caches
+ have merged into this cache.
+
+What: /sys/kernel/slab/cache/align
+Date: May 2007
+KernelVersion: 2.6.22
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The align file is read-only and specifies the cache's object
+ alignment in bytes.
+
+What: /sys/kernel/slab/cache/alloc_calls
+Date: May 2007
+KernelVersion: 2.6.22
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The alloc_calls file is read-only and lists the kernel code
+ locations from which allocations for this cache were performed.
+ The alloc_calls file only contains information if debugging is
+ enabled for that cache (see Documentation/vm/slub.txt).
+
+What: /sys/kernel/slab/cache/alloc_fastpath
+Date: February 2008
+KernelVersion: 2.6.25
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The alloc_fastpath file is read-only and specifies how many
+ objects have been allocated using the fast path.
+ Available when CONFIG_SLUB_STATS is enabled.
+
+What: /sys/kernel/slab/cache/alloc_from_partial
+Date: February 2008
+KernelVersion: 2.6.25
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The alloc_from_partial file is read-only and specifies how
+ many times a cpu slab has been full and it has been refilled
+ by using a slab from the list of partially used slabs.
+ Available when CONFIG_SLUB_STATS is enabled.
+
+What: /sys/kernel/slab/cache/alloc_refill
+Date: February 2008
+KernelVersion: 2.6.25
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The alloc_refill file is read-only and specifies how many
+ times the per-cpu freelist was empty but there were objects
+ available as the result of remote cpu frees.
+ Available when CONFIG_SLUB_STATS is enabled.
+
+What: /sys/kernel/slab/cache/alloc_slab
+Date: February 2008
+KernelVersion: 2.6.25
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The alloc_slab file is read-only and specifies how many times
+ a new slab had to be allocated from the page allocator.
+ Available when CONFIG_SLUB_STATS is enabled.
+
+What: /sys/kernel/slab/cache/alloc_slowpath
+Date: February 2008
+KernelVersion: 2.6.25
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The alloc_slowpath file is read-only and specifies how many
+ objects have been allocated using the slow path because of a
+ refill or allocation from a partial or new slab.
+ Available when CONFIG_SLUB_STATS is enabled.
+
+What: /sys/kernel/slab/cache/cache_dma
+Date: May 2007
+KernelVersion: 2.6.22
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The cache_dma file is read-only and specifies whether objects
+ are from ZONE_DMA.
+ Available when CONFIG_ZONE_DMA is enabled.
+
+What: /sys/kernel/slab/cache/cpu_slabs
+Date: May 2007
+KernelVersion: 2.6.22
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The cpu_slabs file is read-only and displays how many cpu slabs
+ are active and their NUMA locality.
+
+What: /sys/kernel/slab/cache/cpuslab_flush
+Date: April 2009
+KernelVersion: 2.6.31
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The file cpuslab_flush is read-only and specifies how many
+ times a cache's cpu slabs have been flushed as the result of
+ destroying or shrinking a cache, a cpu going offline, or as
+ the result of forcing an allocation from a certain node.
+ Available when CONFIG_SLUB_STATS is enabled.
+
+What: /sys/kernel/slab/cache/ctor
+Date: May 2007
+KernelVersion: 2.6.22
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The ctor file is read-only and specifies the cache's object
+ constructor function, which is invoked for each object when a
+ new slab is allocated.
+
+What: /sys/kernel/slab/cache/deactivate_empty
+Date: February 2008
+KernelVersion: 2.6.25
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The file deactivate_empty is read-only and specifies how many
+ times an empty cpu slab was deactivated.
+ Available when CONFIG_SLUB_STATS is enabled.
+
+What: /sys/kernel/slab/cache/deactivate_full
+Date: February 2008
+KernelVersion: 2.6.25
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The file deactivate_full is read-only and specifies how many
+ times a full cpu slab was deactivated.
+ Available when CONFIG_SLUB_STATS is enabled.
+
+What: /sys/kernel/slab/cache/deactivate_remote_frees
+Date: February 2008
+KernelVersion: 2.6.25
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The file deactivate_remote_frees is read-only and specifies how
+ many times a cpu slab has been deactivated and contained free
+ objects that were freed remotely.
+ Available when CONFIG_SLUB_STATS is enabled.
+
+What: /sys/kernel/slab/cache/deactivate_to_head
+Date: February 2008
+KernelVersion: 2.6.25
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The file deactivate_to_head is read-only and specifies how
+ many times a partial cpu slab was deactivated and added to the
+ head of its node's partial list.
+ Available when CONFIG_SLUB_STATS is enabled.
+
+What: /sys/kernel/slab/cache/deactivate_to_tail
+Date: February 2008
+KernelVersion: 2.6.25
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The file deactivate_to_tail is read-only and specifies how
+ many times a partial cpu slab was deactivated and added to the
+ tail of its node's partial list.
+ Available when CONFIG_SLUB_STATS is enabled.
+
+What: /sys/kernel/slab/cache/destroy_by_rcu
+Date: May 2007
+KernelVersion: 2.6.22
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The destroy_by_rcu file is read-only and specifies whether
+ slabs (not objects) are freed by rcu.
+
+What: /sys/kernel/slab/cache/free_add_partial
+Date: February 2008
+KernelVersion: 2.6.25
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The file free_add_partial is read-only and specifies how many
+ times an object has been freed in a full slab so that it had to
+ added to its node's partial list.
+ Available when CONFIG_SLUB_STATS is enabled.
+
+What: /sys/kernel/slab/cache/free_calls
+Date: May 2007
+KernelVersion: 2.6.22
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The free_calls file is read-only and lists the locations of
+ object frees if slab debugging is enabled (see
+ Documentation/vm/slub.txt).
+
+What: /sys/kernel/slab/cache/free_fastpath
+Date: February 2008
+KernelVersion: 2.6.25
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The free_fastpath file is read-only and specifies how many
+ objects have been freed using the fast path because it was an
+ object from the cpu slab.
+ Available when CONFIG_SLUB_STATS is enabled.
+
+What: /sys/kernel/slab/cache/free_frozen
+Date: February 2008
+KernelVersion: 2.6.25
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The free_frozen file is read-only and specifies how many
+ objects have been freed to a frozen slab (i.e. a remote cpu
+ slab).
+ Available when CONFIG_SLUB_STATS is enabled.
+
+What: /sys/kernel/slab/cache/free_remove_partial
+Date: February 2008
+KernelVersion: 2.6.25
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The file free_remove_partial is read-only and specifies how
+ many times an object has been freed to a now-empty slab so
+ that it had to be removed from its node's partial list.
+ Available when CONFIG_SLUB_STATS is enabled.
+
+What: /sys/kernel/slab/cache/free_slab
+Date: February 2008
+KernelVersion: 2.6.25
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The free_slab file is read-only and specifies how many times an
+ empty slab has been freed back to the page allocator.
+ Available when CONFIG_SLUB_STATS is enabled.
+
+What: /sys/kernel/slab/cache/free_slowpath
+Date: February 2008
+KernelVersion: 2.6.25
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The free_slowpath file is read-only and specifies how many
+ objects have been freed using the slow path (i.e. to a full or
+ partial slab).
+ Available when CONFIG_SLUB_STATS is enabled.
+
+What: /sys/kernel/slab/cache/hwcache_align
+Date: May 2007
+KernelVersion: 2.6.22
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The hwcache_align file is read-only and specifies whether
+ objects are aligned on cachelines.
+
+What: /sys/kernel/slab/cache/min_partial
+Date: February 2009
+KernelVersion: 2.6.30
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ David Rientjes <rientjes@google.com>
+Description:
+ The min_partial file specifies how many empty slabs shall
+ remain on a node's partial list to avoid the overhead of
+ allocating new slabs. Such slabs may be reclaimed by utilizing
+ the shrink file.
+
+What: /sys/kernel/slab/cache/object_size
+Date: May 2007
+KernelVersion: 2.6.22
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The object_size file is read-only and specifies the cache's
+ object size.
+
+What: /sys/kernel/slab/cache/objects
+Date: May 2007
+KernelVersion: 2.6.22
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The objects file is read-only and displays how many objects are
+ active and from which nodes they are from.
+
+What: /sys/kernel/slab/cache/objects_partial
+Date: April 2008
+KernelVersion: 2.6.26
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The objects_partial file is read-only and displays how many
+ objects are on partial slabs and from which nodes they are
+ from.
+
+What: /sys/kernel/slab/cache/objs_per_slab
+Date: May 2007
+KernelVersion: 2.6.22
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The file objs_per_slab is read-only and specifies how many
+ objects may be allocated from a single slab of the order
+ specified in /sys/kernel/slab/cache/order.
+
+What: /sys/kernel/slab/cache/order
+Date: May 2007
+KernelVersion: 2.6.22
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The order file specifies the page order at which new slabs are
+ allocated. It is writable and can be changed to increase the
+ number of objects per slab. If a slab cannot be allocated
+ because of fragmentation, SLUB will retry with the minimum order
+ possible depending on its characteristics.
+
+What: /sys/kernel/slab/cache/order_fallback
+Date: April 2008
+KernelVersion: 2.6.26
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The file order_fallback is read-only and specifies how many
+ times an allocation of a new slab has not been possible at the
+ cache's order and instead fallen back to its minimum possible
+ order.
+ Available when CONFIG_SLUB_STATS is enabled.
+
+What: /sys/kernel/slab/cache/partial
+Date: May 2007
+KernelVersion: 2.6.22
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The partial file is read-only and displays how long many
+ partial slabs there are and how long each node's list is.
+
+What: /sys/kernel/slab/cache/poison
+Date: May 2007
+KernelVersion: 2.6.22
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The poison file specifies whether objects should be poisoned
+ when a new slab is allocated.
+
+What: /sys/kernel/slab/cache/reclaim_account
+Date: May 2007
+KernelVersion: 2.6.22
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The reclaim_account file specifies whether the cache's objects
+ are reclaimable (and grouped by their mobility).
+
+What: /sys/kernel/slab/cache/red_zone
+Date: May 2007
+KernelVersion: 2.6.22
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The red_zone file specifies whether the cache's objects are red
+ zoned.
+
+What: /sys/kernel/slab/cache/remote_node_defrag_ratio
+Date: January 2008
+KernelVersion: 2.6.25
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The file remote_node_defrag_ratio specifies the percentage of
+ times SLUB will attempt to refill the cpu slab with a partial
+ slab from a remote node as opposed to allocating a new slab on
+ the local node. This reduces the amount of wasted memory over
+ the entire system but can be expensive.
+ Available when CONFIG_NUMA is enabled.
+
+What: /sys/kernel/slab/cache/sanity_checks
+Date: May 2007
+KernelVersion: 2.6.22
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The sanity_checks file specifies whether expensive checks
+ should be performed on free and, at minimum, enables double free
+ checks. Caches that enable sanity_checks cannot be merged with
+ caches that do not.
+
+What: /sys/kernel/slab/cache/shrink
+Date: May 2007
+KernelVersion: 2.6.22
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The shrink file is written when memory should be reclaimed from
+ a cache. Empty partial slabs are freed and the partial list is
+ sorted so the slabs with the fewest available objects are used
+ first.
+
+What: /sys/kernel/slab/cache/slab_size
+Date: May 2007
+KernelVersion: 2.6.22
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The slab_size file is read-only and specifies the object size
+ with metadata (debugging information and alignment) in bytes.
+
+What: /sys/kernel/slab/cache/slabs
+Date: May 2007
+KernelVersion: 2.6.22
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The slabs file is read-only and displays how long many slabs
+ there are (both cpu and partial) and from which nodes they are
+ from.
+
+What: /sys/kernel/slab/cache/store_user
+Date: May 2007
+KernelVersion: 2.6.22
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The store_user file specifies whether the location of
+ allocation or free should be tracked for a cache.
+
+What: /sys/kernel/slab/cache/total_objects
+Date: April 2008
+KernelVersion: 2.6.26
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The total_objects file is read-only and displays how many total
+ objects a cache has and from which nodes they are from.
+
+What: /sys/kernel/slab/cache/trace
+Date: May 2007
+KernelVersion: 2.6.22
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ The trace file specifies whether object allocations and frees
+ should be traced.
+
+What: /sys/kernel/slab/cache/validate
+Date: May 2007
+KernelVersion: 2.6.22
+Contact: Pekka Enberg <penberg@cs.helsinki.fi>,
+ Christoph Lameter <cl@linux-foundation.org>
+Description:
+ Writing to the validate file causes SLUB to traverse all of its
+ cache's objects and check the validity of metadata.
diff --git a/Documentation/DocBook/kgdb.tmpl b/Documentation/DocBook/kgdb.tmpl
index 372dec20c8da..5cff41a5fa7c 100644
--- a/Documentation/DocBook/kgdb.tmpl
+++ b/Documentation/DocBook/kgdb.tmpl
@@ -281,7 +281,7 @@
seriously wrong while debugging, it will most often be the case
that you want to enable gdb to be verbose about its target
communications. You do this prior to issuing the <constant>target
- remote</constant> command by typing in: <constant>set remote debug 1</constant>
+ remote</constant> command by typing in: <constant>set debug remote 1</constant>
</para>
</chapter>
<chapter id="KGDBTestSuite">
diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index ec5de02f543f..b121c5db707f 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -1266,13 +1266,22 @@ sctp_rmem - vector of 3 INTEGERs: min, default, max
sctp_wmem - vector of 3 INTEGERs: min, default, max
See tcp_wmem for a description.
-UNDOCUMENTED:
/proc/sys/net/core/*
- dev_weight FIXME
+dev_weight - INTEGER
+ The maximum number of packets that kernel can handle on a NAPI
+ interrupt, it's a Per-CPU variable.
+
+ Default: 64
/proc/sys/net/unix/*
- max_dgram_qlen FIXME
+max_dgram_qlen - INTEGER
+ The maximum length of dgram socket receive queue
+
+ Default: 10
+
+
+UNDOCUMENTED:
/proc/sys/net/irda/*
fast_poll_increase FIXME
diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt
index b716d33912d8..c302ddf629a0 100644
--- a/Documentation/sysctl/vm.txt
+++ b/Documentation/sysctl/vm.txt
@@ -39,8 +39,6 @@ Currently, these files are in /proc/sys/vm:
- nr_hugepages
- nr_overcommit_hugepages
- nr_pdflush_threads
-- nr_pdflush_threads_min
-- nr_pdflush_threads_max
- nr_trim_pages (only if CONFIG_MMU=n)
- numa_zonelist_order
- oom_dump_tasks
@@ -469,32 +467,6 @@ The default value is 0.
==============================================================
-nr_pdflush_threads_min
-
-This value controls the minimum number of pdflush threads.
-
-At boot time, the kernel will create and maintain 'nr_pdflush_threads_min'
-threads for the kernel's lifetime.
-
-The default value is 2. The minimum value you can specify is 1, and
-the maximum value is the current setting of 'nr_pdflush_threads_max'.
-
-See 'nr_pdflush_threads_max' below for more information.
-
-==============================================================
-
-nr_pdflush_threads_max
-
-This value controls the maximum number of pdflush threads that can be
-created. The pdflush algorithm will create a new pdflush thread (up to
-this maximum) if no pdflush threads have been available for >= 1 second.
-
-The default value is 8. The minimum value you can specify is the
-current value of 'nr_pdflush_threads_min' and the
-maximum is 1000.
-
-==============================================================
-
overcommit_memory:
This value contains a flag that enables memory overcommitment.
diff --git a/Documentation/sysfs-rules.txt b/Documentation/sysfs-rules.txt
index 6049a2a84dda..5d8bc2cd250c 100644
--- a/Documentation/sysfs-rules.txt
+++ b/Documentation/sysfs-rules.txt
@@ -113,7 +113,7 @@ versions of the sysfs interface.
"devices" directory at /sys/subsystem/<name>/devices.
If /sys/subsystem exists, /sys/bus, /sys/class and /sys/block can be
- ignored. If it does not exist, you have always to scan all three
+ ignored. If it does not exist, you always have to scan all three
places, as the kernel is free to move a subsystem from one place to
the other, as long as the devices are still reachable by the same
subsystem name.