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Lift all the snapshot utilities (merge, split, combine)
out of the monolithic lvconvert implementation, using
the command definitions. The old code associated with
these commands is now unused and will be removed separately.
This lifts the lvconvert --repair and --replace commands
out of the monolithic lvconvert implementation. The
previous calls into repair/replace can no longer be
reached and will be removed in a separate commit.
The new check_single_lv() function is called prior to the
existing process_single_lv(). If the check function returns 0,
the LV will not be processed.
The check_single_lv function is meant to be a standard method
to validate the combination of specific command + specific LV,
and decide if the combination is allowed. The check_single
function can be used by anything that calls process_each_lv.
As commands are migrated to take advantage of command
definitions, each command definition gets its own entry
point which calls process_each for itself, passing a
pair of check_single/process_single functions which can
be specific to the narrowly defined command def.
. Define a prototype for every lvm command.
. Match every user command with one definition.
. Generate help text and man pages from them.
The new file command-lines.in defines a prototype for every
unique lvm command. A unique lvm command is a unique
combination of: command name + required option args +
required positional args. Each of these prototypes also
includes the optional option args and optional positional
args that the command will accept, a description, and a
unique string ID for the definition. Any valid command
will match one of the prototypes.
Here's an example of the lvresize command definitions from
command-lines.in, there are three unique lvresize commands:
lvresize --size SizeMB LV
OO: --alloc Alloc, --autobackup Bool, --force,
--nofsck, --nosync, --noudevsync, --reportformat String, --resizefs,
--stripes Number, --stripesize SizeKB, --poolmetadatasize SizeMB
OP: PV ...
ID: lvresize_by_size
DESC: Resize an LV by a specified size.
lvresize LV PV ...
OO: --alloc Alloc, --autobackup Bool, --force,
--nofsck, --nosync, --noudevsync,
--reportformat String, --resizefs, --stripes Number, --stripesize SizeKB
ID: lvresize_by_pv
DESC: Resize an LV by specified PV extents.
FLAGS: SECONDARY_SYNTAX
lvresize --poolmetadatasize SizeMB LV_thinpool
OO: --alloc Alloc, --autobackup Bool, --force,
--nofsck, --nosync, --noudevsync,
--reportformat String, --stripes Number, --stripesize SizeKB
OP: PV ...
ID: lvresize_pool_metadata_by_size
DESC: Resize a pool metadata SubLV by a specified size.
The three commands have separate definitions because they have
different required parameters. Required parameters are specified
on the first line of the definition. Optional options are
listed after OO, and optional positional args are listed after OP.
This data is used to generate corresponding command definition
structures for lvm in command-lines.h. usage/help output is also
auto generated, so it is always in sync with the definitions.
Example of the corresponding generated structure in
command-lines.h for the first lvresize prototype
(these structures are never edited directly):
commands[83].name = "lvresize";
commands[83].command_line_id = "lvresize_by_size";
commands[83].command_line_enum = lvresize_by_size_CMD;
commands[83].fn = lvresize;
commands[83].ro_count = 1;
commands[83].rp_count = 1;
commands[83].oo_count = 22;
commands[83].op_count = 1;
commands[83].cmd_flags = 0;
commands[83].desc = "DESC: Resize an LV by a specified size.";
commands[83].usage = "lvresize --size Number[m|unit] LV"
" [ --resizefs, --poolmetadatasize Number[m|unit], COMMON_OPTIONS ]"
" [ PV ... ]";
commands[83].usage_common =
" [ --alloc contiguous|cling|cling_by_tags|normal|anywhere|inherit, --nosync, --reportformat String, --autobackup y|n, --stripes Number, --stripesize Number[k|unit], --nofsck, --commandprofile String, --config String, --debug, --driverloaded y|n, --help, --profile String, --quiet, --verbose, --version, --yes, --test, --force, --noudevsync ]";
commands[83].required_opt_args[0].opt = size_ARG;
commands[83].required_opt_args[0].def.val_bits = val_enum_to_bit(sizemb_VAL);
commands[83].required_pos_args[0].pos = 1;
commands[83].required_pos_args[0].def.val_bits = val_enum_to_bit(lv_VAL);
commands[83].optional_opt_args[0].opt = commandprofile_ARG;
commands[83].optional_opt_args[0].def.val_bits = val_enum_to_bit(string_VAL);
commands[83].optional_opt_args[1].opt = config_ARG;
commands[83].optional_opt_args[1].def.val_bits = val_enum_to_bit(string_VAL);
commands[83].optional_opt_args[2].opt = debug_ARG;
commands[83].optional_opt_args[3].opt = driverloaded_ARG;
commands[83].optional_opt_args[3].def.val_bits = val_enum_to_bit(bool_VAL);
commands[83].optional_opt_args[4].opt = help_ARG;
commands[83].optional_opt_args[5].opt = profile_ARG;
commands[83].optional_opt_args[5].def.val_bits = val_enum_to_bit(string_VAL);
commands[83].optional_opt_args[6].opt = quiet_ARG;
commands[83].optional_opt_args[7].opt = verbose_ARG;
commands[83].optional_opt_args[8].opt = version_ARG;
commands[83].optional_opt_args[9].opt = yes_ARG;
commands[83].optional_opt_args[10].opt = test_ARG;
commands[83].optional_opt_args[11].opt = alloc_ARG;
commands[83].optional_opt_args[11].def.val_bits = val_enum_to_bit(alloc_VAL);
commands[83].optional_opt_args[12].opt = autobackup_ARG;
commands[83].optional_opt_args[12].def.val_bits = val_enum_to_bit(bool_VAL);
commands[83].optional_opt_args[13].opt = force_ARG;
commands[83].optional_opt_args[14].opt = nofsck_ARG;
commands[83].optional_opt_args[15].opt = nosync_ARG;
commands[83].optional_opt_args[16].opt = noudevsync_ARG;
commands[83].optional_opt_args[17].opt = reportformat_ARG;
commands[83].optional_opt_args[17].def.val_bits = val_enum_to_bit(string_VAL);
commands[83].optional_opt_args[18].opt = resizefs_ARG;
commands[83].optional_opt_args[19].opt = stripes_ARG;
commands[83].optional_opt_args[19].def.val_bits = val_enum_to_bit(number_VAL);
commands[83].optional_opt_args[20].opt = stripesize_ARG;
commands[83].optional_opt_args[20].def.val_bits = val_enum_to_bit(sizekb_VAL);
commands[83].optional_opt_args[21].opt = poolmetadatasize_ARG;
commands[83].optional_opt_args[21].def.val_bits = val_enum_to_bit(sizemb_VAL);
commands[83].optional_pos_args[0].pos = 2;
commands[83].optional_pos_args[0].def.val_bits = val_enum_to_bit(pv_VAL);
commands[83].optional_pos_args[0].def.flags = ARG_DEF_FLAG_MAY_REPEAT;
Every user-entered command is compared against the set of
command structures, and matched with one. An error is
reported if an entered command does not have the required
parameters for any definition. The closest match is printed
as a suggestion, and running lvresize --help will display
the usage for each possible lvresize command.
The prototype syntax used for help/man output includes
required --option and positional args on the first line,
and optional --option and positional args enclosed in [ ]
on subsequent lines.
command_name <required_opt_args> <required_pos_args>
[ <optional_opt_args> ]
[ <optional_pos_args> ]
$ lvresize --help
lvresize - Resize a logical volume
Resize an LV by a specified size.
lvresize --size Number[m|unit] LV
[ --resizefs,
--poolmetadatasize Number[m|unit],
COMMON_OPTIONS ]
[ PV ... ]
Resize a pool metadata SubLV by a specified size.
lvresize --poolmetadatasize Number[m|unit] LV_thinpool
[ COMMON_OPTIONS ]
[ PV ... ]
Common options:
[ --alloc contiguous|cling|cling_by_tags|normal|anywhere|inherit,
--nosync,
--reportformat String,
--autobackup y|n,
--stripes Number,
--stripesize Number[k|unit],
--nofsck,
--commandprofile String,
--config String,
--debug,
--driverloaded y|n,
--help,
--profile String,
--quiet,
--verbose,
--version,
--yes,
--test,
--force,
--noudevsync ]
(Use --help --help for usage notes.)
$ lvresize --poolmetadatasize 4
Failed to find a matching command definition.
Closest command usage is:
lvresize --poolmetadatasize Number[m|unit] LV_thinpool
Command definitions that are not to be advertised/suggested
have the flag SECONDARY_SYNTAX. These commands will not be
printed in the normal help output.
Man page prototypes are also generated from the same original
command definitions, and are always in sync with the code
and help text.
Very early in command execution, a matching command definition
is found. lvm then knows the operation being done, and that
the provided args conform to the definition. This will allow
lots of ad hoc checking/validation to be removed throughout
the code.
Each command definition can also be routed to a specific
function to implement it. The function is associated with
an enum value for the command definition (generated from
the ID string.) These per-command-definition implementation
functions have not yet been created, so all commands
currently fall back to the existing per-command-name
implementation functions.
Using per-command-definition functions will allow lots of
code to be removed which tries to figure out what the
command is meant to do. This is currently based on ad hoc
and complicated option analysis. When using the new
functions, what the command is doing is already known
from the associated command definition.
So, this first phase validates every user-entered command
against the set of command prototypes, then calls the existing
implementation. The second phase can associate an implementation
function with each definition, and take further advantage of the
known operation to avoid the complicated option analysis.
Handle files that contain multiple logical extents in a single
physical extent properly:
- In FIEMAP terms a logical extent is a contiguous range of
sectors in the file's address space.
- One or more physically adjacent logical extents comprise a
physical extent: these are the disk areas that will be mapped
to regions.
- An extent boundary occurs when the start sector of extent
n+1 is not equal to (n.start + n.length).
This requires that we accumulate the length values of extents
returned by FIEMAP until a discontinuity is found (since each
struct fiemap_extent returned by FIEMAP only represents a single
logical extent, which may be contiguous with other logical
extents on-disk).
This avoids creating large numbers of regions for physically
adjacent (logical) extents and fixes the earlier behaviour which
would only map the first logical extent of the physical extent,
leaving gaps in the region table for these files.
To be able to detect lvm2 command is not leaking some
'unexpected' device - remove all devices before
test exits by its own command so test teardown
now can check what was 'left' unexpectedly.
Fix order of operation when converting raid1 into old mirror.
Before any later metadata modification are initiated prepare
mirror_log device with all clearing.
Then directly convert raid1 into mirror with mirror_log.
This convertion now properly see as precommitted metadata
new 'mirror' and committed old 'raid' and is able to
preload all LVs.
When mapping regions to a file descriptor, a temporary table of
extent descriptors is built using the dm_pool object building
interface.
Previously this use borrowed the dms->mem region and counter
table pool (since nothing can interleave with the allocation
while the caller is still in dm_stats_create_regions_from_fd()).
This turns out to be problematic for error recovery. When a
region creation operation fails partway through file mapping,
we need to roll back the set of already created regions and
this requires a listed handle: the dm_stats_list() will then
allocate from the same pool as the extents; we either have
to throw away valid list data, or leak the extent table, to
return the handle in a valid state.
Avoid this problem by creating a new, temporary mem pool in
_stats_create_file_regions() to hold the extent data, and
discarding it on exit from the function.
While cleaning up the table of already created regions during a
failed dm_stats_create_regions_from_fd(), list the handle once,
and call _stats_delete_region() directly. This avoids sending a
@stats_list message for each region deleted, reducing runtime
from 6s to 0.7s when cleaning up ~250 out of ~10000 regions:
# time dmstats create --filemap b.img
device-mapper: message ioctl on (253:0) failed: Cannot allocate memory
Failed to create region 246 of 309 at 9388032.
Could not create regions from file /root/b.img
<< pauses here >>
Command failed
real 0m6.267s
user 0m3.770s
sys 0m2.487s
# time dmstats create --filemap b.img
device-mapper: message ioctl on (253:0) failed: Cannot allocate memory
Failed to create region 246 of 309 at 9388032.
Could not create regions from file /root/b.img
Command failed
real 0m0.716s
user 0m0.034s
sys 0m0.581s
Testing the error path requires region creation to start to
fail part way through the operation (in order to have regions
to clean up): the simplest way is to ensure the system is
close to the kernel limit of 1/4 RAM or 1/2 vmalloc space
consumed by dmstats data.
Split dm_stats_delete_region() so that internal callers can manage
the handle state themselves.
dm_stats_delete_region() now just handles checking the state of the
handle, reporting validation errors, and calling dm_stats_list() if
necessary, before calling _stats_delete_region().
The new _stats_delete_region() function performs the actual group
member removal and region deletion, and requires a fully listed
handle to operate.
Callers that repeatedly delete regions can use a single listed
handle for many operations on the same device, avoiding one
message ioctl per region deleted: since @stats_list with many
regions is expensive, this yields large runtime improvements.
If we fail to create a region during dm_stats_create_regions_from_fd(),
we must remove all regions that were created to do this to date. This
needs to loop over the table of region_id values that were populated
by _stats_create_file_regions() before the error.
The code for this failure case in the out_remove branch incorrectly
uses the table index as the region_id:
for (--i; i != DM_STATS_REGION_NOT_PRESENT; i--) {
if (!dm_stats_delete_region(dms, i))
log_error("Could not delete region " FMTu64 ".", i);
}
This causes the cleanup code to delete a completely unrelated set
of regions (since the index here will always be nr_regions..0).
Fix it to pass the actual region_id stored in regions[i] instead.
Fix a silly bug in dm_stats_delete_region() that hugely inflates
runtimes when deleting a large number of regions.
For ~50,000 regions this change reduces the runtime from 98s to
6s on my test systems (a ~93% reduction).
The bug exists because dm_stats_delete_region() applies a truth
test to the return value of dm_stats_get_nr_areas(); this is
never correct usage - it will walk the entire region table and
calculate area counts for each region (which is roughly O(n^2)
in the number of regions, as dm_stats_delete_region() is being
called inside a region walk).
Although the individual area calculation is not that costly,
uselessly running anything 2,500,000,000 times over gets a bit
slow.
A much cheaper test (which is always true if the areas check is
true) is to just test dm_stats_get_nr_regions() or dms->regions;
if either is true it implies at least one area exists.
Old:
Performance counter stats for 'dmstats delete --allregions --alldevices':
98117.791458 task-clock (msec) # 1.000 CPUs utilized
127 context-switches # 0.001 K/sec
3 cpu-migrations # 0.000 K/sec
6,631 page-faults # 0.068 K/sec
307,711,724,562 cycles # 3.136 GHz
544,762,959,577 instructions # 1.77 insn per cycle
84,287,824,115 branches # 859.047 M/sec
2,538,875 branch-misses # 0.00% of all branches
98.119578733 seconds time elapsed
New:
Performance counter stats for 'dmstats delete --allregions --alldevices':
6427.251074 task-clock (msec) # 1.000 CPUs utilized
6 context-switches # 0.001 K/sec
0 cpu-migrations # 0.000 K/sec
6,634 page-faults # 0.001 M/sec
21,613,018,724 cycles # 3.363 GHz
3,794,755,445 instructions # 0.18 insn per cycle
852,974,026 branches # 132.712 M/sec
808,625 branch-misses # 0.09% of all branches
6.428953647 seconds time elapsed
