[v3,00/38] multipath-tools: user-friendly names rework

Message

Martin Wilck Sept. 14, 2023, 2:51 p.m. UTC

From: Martin Wilck <[e-mail]>

This patch set contains a two-step rework of the user-friendly
names code. Patch 2-5 change the current code such that it (well, almost)
never attempts to use an alias that is currently in use by another
map. We already have some checks for this, but they don't cover all
possible scenarios. Patch 6-10 add some units tests for
get_user_friendly_alias(), and restructure the unit tests somewhat.

In the second part of the set, Patch 11-18 restructure the alias code such
that we don't read the bindings file every time an alias is
requested. Instead, we just use a memory cache of the current bindings, and
re-write the file only if a new binding is added.  This reduces the number of
system calls and simplifies the code.

Patch 19 applies the changes to the unit tests that become
necessary because of the previous patches. Patch 20/21 add another
optimization for the alias_already_taken() test.

Patch 22-23 introduce a solution for the problem discussed in the review
of v1 of this patch set, the partial ordering of aliases in memory.
By sorting first be string length, and then alphabetically, we obtain
a total "numeric" ordering for every given alias prefix. This ordering
allows simplifying the search for "gaps" in the list of aliases, which
is done in patch 24-26.

As discussed in the opening letter of the v1 patch series, the patch
series has the effect that the bindings file is not re-read every time
a new binding is attempted. Patch 28 and 29 introduce a notification
mechanism for multipathd which causes the bindings to be re-read
when the bindings file has been updated.

Patch 30-36 are a series of minor fixes for the build system and the
documentation. Most imporantly, the man pages will now show the correct
paths for various built-in defaults.

Finally, patch 37 (which is deliberately kept separate and at the end of the
series, in order to allow downstream integrators to skip it) eventually
deprecates the runtime configuration options for bindings_file, wwids_file,
and prkeys_file.

Patch 1 is a separate, independent fix.

NOTE: my main test bed is currently unavailable, therefore this set has
yet reveived less testing than usual. I have tested this to the extent
I currently can, but further testing will be highly appreciated.

To avoid spam, I'm not re-posting the patches that already got Ben's
"Reviewed-by:" tag.

Reviews and comments welcome.

# Changes v1 -> v2:

* Patch 03: skipped superfluous test for the case where a map already
  has an alias (Ben Marzinski)
* Patch 07: removed invalid tests for the case where the already assigned
  alias of a given map is assigned to a different wwid (Ben Marzinski)
* Patch 09/10: moved some macro-usage fixes from 10 to 09
* Patch 18:
  - skipped superfluous tests like in patch 03 (Ben Marzinski)
  - fix bug in get_user_friendly_wwid() (Ben Marzinski)
* Added patch 22 ff. (see above).

# Changes v2 -> v3:

* Patch 26: avoid negative array index (Ben Marzinski)
* Patch 27:
  - assign old_bindings under bindings_mutex (Ben Marzinski)
  - move condlog after timestamp update in update_bindings_file() (Ben, me)
  - add read_bindings_file() call in get_user_friendly_wwid() (Ben)
  - fix return value check of fread() (Ben)
  - remove superfluous test in _read_bindings_file() (Ben)
  - avoid compilation error on Jessie for initialization of struct timespec (me)
* Patch 38: added to fix a compilation error with gcc 12 and liburcu < 0.14

Martin Wilck (38):
  libmultipath: sysfs_set_scsi_tmo: do nothing for ACT_DRY_RUN
  libmultipath: add alias_already_taken()
  libmultipath: unify use_existing_alias() and get_user_friendly_alias()
  libmultipath: never allocate an alias that's already taken
  libmultipath: lookup_binding: add comment about the algorithm
  multipath-tools test: simplify debugging for condlog mismatch
  multipath-tools tests: add tests for get_user_friendly_alias()
  multipath-tools test: consistent use of macros in alias test
  multipath-tools tests: convert mock_{failed,used}_alias to macros
  multipath-tools test: use mock_bindings_file() consistently
  libmultipath: add global variable for current bindings
  libmultipath: rename fix_bindings_file() to update_bindings_file()
  libmultipath: alias.c: move bindings related code up
  libmultipath: update_bindings_file: take filename argument
  libmultipath: update_bindings_file: use a single write()
  libmultipath: update_bindings_file: don't log temp file name
  libmultipath: alias.c: factor out read_binding()
  libmultipath: keep bindings in memory
  multipath-tools tests: fix alias tests
  libmultipath: dm_get_uuid(): return emtpy UUID for non-existing maps
  libmultipath: adapt to new semantics of dm_get_uuid()
  libmultipath: sort aliases by length and strcmp
  multipath-tools tests: fix alias test after sort order change
  libmultipath: simplify get_free_id() assuming total ordering
  multipath-tools tests: adapt alias tests for total ordering
  multipath-tools tests: add test for ordering of bindings
  multipathd: watch bindings file with inotify + timestamp
  multipath-tools tests: mock pthread_mutex_{lock,unlock}
  multipath-tools Makefile: sanitize paths for configuration files
  multipath-tools: add compile time configuration for "/etc/multipath"
  multipath-tools man pages: generate with correct paths
  libdmmp/Makefile: fix bug in install section
  multipath-tools: README.md: improve documentation for compile-time
    options
  libmultipath: print built-in values for deprecated options
  multipath: add a missing newline
  multipath-tools: allow prefixes with and w/o trailing slash
  libmultipath: deprecate bindings_file, wwids_file, prkeys_file
  libmultipath: avoid -Warray-bounds error in uatomic operations

 .gitignore                                    |    4 +
 Makefile.inc                                  |   45 +-
 README.md                                     |   38 +-
 create-config.mk                              |    5 +
 libdmmp/Makefile                              |    2 +-
 libmultipath/alias.c                          | 1043 +++++++-----
 libmultipath/alias.h                          |   14 +-
 libmultipath/config.c                         |   18 -
 libmultipath/config.h                         |    3 -
 libmultipath/configure.c                      |    7 +-
 libmultipath/defaults.h                       |    7 +-
 libmultipath/devmapper.c                      |   10 +-
 libmultipath/dict.c                           |   55 +-
 libmultipath/discovery.c                      |    3 +
 libmultipath/libmultipath.version             |    4 +-
 libmultipath/lock.h                           |   23 +-
 libmultipath/prkey.c                          |    7 +-
 libmultipath/prkey.h                          |    7 +-
 libmultipath/propsel.c                        |   20 +-
 libmultipath/wwids.c                          |   18 +-
 mpathpersist/Makefile                         |    5 +-
 .../{mpathpersist.8 => mpathpersist.8.in}     |    2 +-
 multipath/Makefile                            |   13 +-
 multipath/main.c                              |    6 +-
 multipath/{multipath.8 => multipath.8.in}     |   10 +-
 .../{multipath.conf.5 => multipath.conf.5.in} |   44 +-
 multipathd/Makefile                           |   11 +-
 multipathd/main.c                             |    1 +
 multipathd/{multipathd.8 => multipathd.8.in}  |    8 +-
 multipathd/uxlsnr.c                           |   29 +-
 tests/Makefile                                |    1 +
 tests/alias.c                                 | 1491 +++++++++++++----
 tests/test-log.c                              |    4 +-
 33 files changed, 1983 insertions(+), 975 deletions(-)
 rename mpathpersist/{mpathpersist.8 => mpathpersist.8.in} (99%)
 rename multipath/{multipath.8 => multipath.8.in} (97%)
 rename multipath/{multipath.conf.5 => multipath.conf.5.in} (98%)
 rename multipathd/{multipathd.8 => multipathd.8.in} (97%)