This pair of calls allows plugins to describe which extents in the virtual disk are allocated, holes or zeroes. --- docs/nbdkit-filter.pod | 107 ++++++++ docs/nbdkit-plugin.pod | 103 +++++++ include/nbdkit-common.h | 10 +- include/nbdkit-filter.h | 25 +- include/nbdkit-plugin.h | 6 +- server/internal.h | 5 + server/extents.c | 574 ++++++++++++++++++++++++++++++++++++++++ server/filters.c | 61 +++++ server/plugins.c | 56 +++- server/test-extents.c | 151 +++++++++++ .gitignore | 1 + server/Makefile.am | 18 +- 12 files changed, 1111 insertions(+), 6 deletions(-) diff --git a/docs/nbdkit-filter.pod b/docs/nbdkit-filter.pod index dc9a262..7b25c8e 100644 --- a/docs/nbdkit-filter.pod +++ b/docs/nbdkit-filter.pod @@ -350,6 +350,8 @@ calls. =head2 C<.can_zero> +=head2 C<.can_extents> + =head2 C<.can_fua> =head2 C<.can_multi_conn> @@ -365,6 +367,8 @@ calls. void *handle); int (*can_zero) (struct nbdkit_next_ops *next_ops, void *nxdata, void *handle); + int (*can_extents) (struct nbdkit_next_ops *next_ops, void *nxdata, + void *handle); int (*can_fua) (struct nbdkit_next_ops *next_ops, void *nxdata, void *handle); int (*can_multi_conn) (struct nbdkit_next_ops *next_ops, void *nxdata, @@ -513,6 +517,109 @@ value to return to the client. The filter should never fail with C<EOPNOTSUPP> (while plugins have automatic fallback to C<.pwrite>, filters do not). +=head2 C<.extents> + + int (*extents) (struct nbdkit_next_ops *next_ops, void *nxdata, + void *handle, uint32_t count, uint64_t offset, uint32_t flags, + struct nbdkit_extents_map *extents_map, + int *err); + +This intercepts the plugin C<.extents> method and can be used to +modify extent requests. + +This function will not be called if C<.can_extents> returned false; in +turn, the filter should not call C<next_ops-E<gt>extents> if +C<next_ops-E<gt>can_extents> did not return true. + +The C<extents_map> parameter passed to this function is empty +(representing a fully allocated disk). If the filter does not need to +adjust extents from the underlying plugin it can simply pass this +through to the layer below: + + myfilter_extents (...) + { + return next_ops->extents (nxdata, count, offset, flags, + extents_map, err); + } + +It is also possible for filters to transform the extents map received +back from the layer below. Usually this must be done by allocating a +new, empty map which is passed to the layer below. Without error +handling it would look like this: + + myfilter_extents (...) + { + struct nbdkit_extents_map *map2 = nbdkit_extents_new (); + next_ops->extents (nxdata, count, offset, flags, map2, err); + /* transform map2 and return results in extents_map */ + nbdkit_extents_foreach (map2, transform_offset, extents_map, /*..*/); + nbdkit_extents_free (map2); + } + +If there is an error, C<.extents> should call C<nbdkit_error> with an +error message B<and> return -1 with C<err> set to the positive errno +value to return to the client. + +=head3 Allocating and freeing nbdkit_extents_map + +Two functions are provided to filters only for allocating and freeing +the map: + + struct nbdkit_extents_map *nbdkit_extents_new (); + +Allocates and returns a new, empty extents map. The initial state is +that the whole disk is allocated with data. + +On error this function can return C<NULL>. In this case it calls +C<nbdkit_error> and/or C<nbdkit_set_error> as required. + + void nbdkit_extents_free (struct nbdkit_extents_map *); + +Frees an existing extents map. + +=head3 Iterating over nbdkit_extents_map + +One function is provided to filters only to iterate over the extents +map: + + typedef int (*nbdkit_extents_callback) (uint64_t offset, uint64_t length, + uint32_t type, void *opaque); + + int nbdkit_extents_foreach ( + const struct nbdkit_extents_map *extents_map, + nbdkit_extents_callback fn, void *opaque, + uint32_t flags, + uint64_t range_offset, uint64_t range_length); + +Iterate over the extents in ascending order, calling C<fn> for each. +C<fn> should return 0 on success or -1 on failure. If a call to C<fn> +fails then C<nbdkit_extents_foreach> also fails immediately. + +C<nbdkit_extents_foreach> returns C<0> on success or C<-1> on failure. +On internal failures it calls C<nbdkit_error> or C<nbdkit_set_error>. +If C<fn> fails it is expected that C<fn> calls those functions as +necessary. + +The C<flags> parameter can contain: + +=over 4 + +=item C<NBDKIT_EXTENTS_FOREACH_FLAG_ONE> + +Only call C<fn> for the first extent, and then return. (This is used +to implement C<NBD_CMD_FLAG_REQ_ONE> in the NBD protocol.) + +=item C<NBDKIT_EXTENTS_FOREACH_FLAG_RANGE> + +If this flag is included then the C<range_offset> and C<range_length> +parameters are used, so only extents overlapping +C<[range_offset...range_offset+range_length-1]> are returned. + +If this flag is not included in C<flags> then the range parameters are +I<ignored>. + +=back + =head1 ERROR HANDLING If there is an error in the filter itself, the filter should call diff --git a/docs/nbdkit-plugin.pod b/docs/nbdkit-plugin.pod index 47545f3..7b7b38b 100644 --- a/docs/nbdkit-plugin.pod +++ b/docs/nbdkit-plugin.pod @@ -555,6 +555,20 @@ This callback is not required. If omitted, then nbdkit always tries C<.zero> first if it is present, and gracefully falls back to C<.pwrite> if C<.zero> was absent or failed with C<EOPNOTSUPP>. +=head2 C<.can_extents> + + int can_extents (void *handle); + +This is called during the option negotiation phase to find out if the +plugin supports detecting allocated (non-sparse) regions of the disk +with the C<.extents> callback. + +If there is an error, C<.can_extents> should call C<nbdkit_error> with +an error message and return C<-1>. + +This callback is not required. If omitted, then we return true iff a +C<.extents> callback has been defined. + =head2 C<.can_fua> int can_fua (void *handle); @@ -717,6 +731,95 @@ If there is an error, C<.zero> should call C<nbdkit_error> with an error message, and C<nbdkit_set_error> to record an appropriate error (unless C<errno> is sufficient), then return C<-1>. +=head2 C<.extents> + + int extents (void *handle, uint32_t count, uint64_t offset, + uint32_t flags, + struct nbdkit_extents_map *extents_map); + +During the data serving phase, this callback is used to detect +allocated, sparse and zeroed regions of the disk. + +This function will not be called if C<.can_extents> returned false. +nbdkit's default behaviour in this case is to treat the whole virtual +disk as if it was allocated. + +The callback should detect and return the list of extents overlapping +the range C<[offset...offset+count-1]>. The C<extents_map> parameter +points to an opaque object which the callback should fill in by +calling C<nbdkit_extent_add> etc. See L</Extents map> below. + +The C<flags> parameter may contain the flag C<NBDKIT_FLAG_REQ_ONE> +which means that the client is only requesting information about the +extent overlapping C<offset>. The plugin may ignore this flag, or as +an optimization it may return just a single extent for C<offset>. +(Note that implementing this optimization correctly is difficult and +subtle. You must ensure that the upper limit of the single extent +returned is correct. If unsure then the safest option is to ignore +this flag.) + +If there is an error, C<.extents> should call C<nbdkit_error> with an +error message, and C<nbdkit_set_error> to record an appropriate error +(unless C<errno> is sufficient), then return C<-1>. + +=head3 Extents map + +The plugin C<extents> callback is passed an opaque pointer C<struct +nbdkit_extents_map *extents_map>. This structure represents a list of +L<filesystem extents|https://en.wikipedia.org/wiki/Extent_(file_systems)> +describing which areas of the disk are allocated, which are sparse +(“holes”), and, if supported, which are zeroes. Initially the map +describes a single allocated data extent covering the entire virtual +disk. + +The C<extents> callback has to fill in any holes or zeroes areas by +calling C<nbdkit_extent*> functions, to describe all extents +overlapping the range C<[offset...offset+count-1]>. (nbdkit will +ignore extents outside this range so plugins may, if it is easier to +implement, return all extent information for the whole disk.) + +The following functions are available for plugins or filters to call: + + int nbdkit_extent_add (struct nbdkit_extents_map *extents_map, + uint64_t offset, uint64_t length, uint32_t type); + +Add an extent covering C<[offset...offset+length-1]> of one of +the following four types: + +=over 4 + +=item C<type = 0> + +A normal, allocated data extent. + +=item C<type = NBDKIT_EXTENT_HOLE|NBDKIT_EXTENT_ZERO> + +An unallocated extent, a.k.a. a “hole”, which reads back as zeroes. +This is the normal type of hole applicable to most disks. + +=item C<type = NBDKIT_EXTENT_ZERO> + +An allocated extent which is known to contain only zeroes. + +=item C<type = NBDKIT_EXTENT_HOLE> + +An unallocated extent (hole) which does not read back as zeroes. Note +this should only be used in specialized circumstances such as when +writing a plugin for (or to emulate) certain SCSI drives which do not +guarantee that trimmed blocks read back as zeroes. + +=back + +If the new extent overlaps some previous extent in the map then the +overlapping part(s) are overwritten with the new type. Adjacent +extents of the same type may also be coalesced. Thus you shouldn't +assume that C<nbdkit_extent_add> always adds exactly one more extent +to the map. + +C<nbdkit_extent_add> returns C<0> on success or C<-1> on failure. On +failure C<nbdkit_error> and/or C<nbdkit_set_error> has already been +called. + =head1 THREADS Each nbdkit plugin must declare its thread safety model by defining diff --git a/include/nbdkit-common.h b/include/nbdkit-common.h index cb9954e..8526171 100644 --- a/include/nbdkit-common.h +++ b/include/nbdkit-common.h @@ -1,5 +1,5 @@ /* nbdkit - * Copyright (C) 2013-2018 Red Hat Inc. + * Copyright (C) 2013-2019 Red Hat Inc. * All rights reserved. * * Redistribution and use in source and binary forms, with or without @@ -60,11 +60,15 @@ extern "C" { #define NBDKIT_FLAG_MAY_TRIM (1<<0) /* Maps to !NBD_CMD_FLAG_NO_HOLE */ #define NBDKIT_FLAG_FUA (1<<1) /* Maps to NBD_CMD_FLAG_FUA */ +#define NBDKIT_FLAG_REQ_ONE (1<<2) /* Maps to NBD_CMD_FLAG_REQ_ONE */ #define NBDKIT_FUA_NONE 0 #define NBDKIT_FUA_EMULATE 1 #define NBDKIT_FUA_NATIVE 2 +#define NBDKIT_EXTENT_HOLE (1<<0) /* Same as NBD_STATE_HOLE */ +#define NBDKIT_EXTENT_ZERO (1<<1) /* Same as NBD_STATE_ZERO */ + extern void nbdkit_error (const char *msg, ...) ATTRIBUTE_FORMAT_PRINTF (1, 2); extern void nbdkit_verror (const char *msg, va_list args); extern void nbdkit_debug (const char *msg, ...) ATTRIBUTE_FORMAT_PRINTF (1, 2); @@ -76,6 +80,10 @@ extern int nbdkit_parse_bool (const char *str); extern int nbdkit_read_password (const char *value, char **password); extern char *nbdkit_realpath (const char *path); +struct nbdkit_extents_map; +extern int nbdkit_extent_add (struct nbdkit_extents_map *, + uint64_t offset, uint64_t length, uint32_t type); + /* A static non-NULL pointer which can be used when you don't need a * per-connection handle. */ diff --git a/include/nbdkit-filter.h b/include/nbdkit-filter.h index 71c06c8..4efb98e 100644 --- a/include/nbdkit-filter.h +++ b/include/nbdkit-filter.h @@ -1,5 +1,5 @@ /* nbdkit - * Copyright (C) 2013-2018 Red Hat Inc. + * Copyright (C) 2013-2019 Red Hat Inc. * All rights reserved. * * Redistribution and use in source and binary forms, with or without @@ -44,6 +44,19 @@ extern "C" { #define NBDKIT_FILTER_API_VERSION 2 +#define NBDKIT_EXTENTS_FOREACH_FLAG_ONE 1 +#define NBDKIT_EXTENTS_FOREACH_FLAG_RANGE 2 + +extern struct nbdkit_extents_map *nbdkit_extents_new (void); +extern void nbdkit_extents_free (struct nbdkit_extents_map *); +typedef int (*nbdkit_extents_callback) (uint64_t offset, uint64_t length, + uint32_t type, void *opaque); +extern int nbdkit_extents_foreach (const struct nbdkit_extents_map *, + nbdkit_extents_callback fn, void *opaque, + uint32_t flags, + uint64_t range_offset, + uint64_t range_length); + typedef int nbdkit_next_config (void *nxdata, const char *key, const char *value); typedef int nbdkit_next_config_complete (void *nxdata); @@ -58,6 +71,7 @@ struct nbdkit_next_ops { int (*is_rotational) (void *nxdata); int (*can_trim) (void *nxdata); int (*can_zero) (void *nxdata); + int (*can_extents) (void *nxdata); int (*can_fua) (void *nxdata); int (*can_multi_conn) (void *nxdata); @@ -71,6 +85,9 @@ struct nbdkit_next_ops { int *err); int (*zero) (void *nxdata, uint32_t count, uint64_t offset, uint32_t flags, int *err); + int (*extents) (void *nxdata, uint32_t count, uint64_t offset, uint32_t flags, + struct nbdkit_extents_map *extents_map, + int *err); }; struct nbdkit_filter { @@ -120,6 +137,8 @@ struct nbdkit_filter { void *handle); int (*can_zero) (struct nbdkit_next_ops *next_ops, void *nxdata, void *handle); + int (*can_extents) (struct nbdkit_next_ops *next_ops, void *nxdata, + void *handle); int (*can_fua) (struct nbdkit_next_ops *next_ops, void *nxdata, void *handle); int (*can_multi_conn) (struct nbdkit_next_ops *next_ops, void *nxdata, @@ -140,6 +159,10 @@ struct nbdkit_filter { int (*zero) (struct nbdkit_next_ops *next_ops, void *nxdata, void *handle, uint32_t count, uint64_t offset, uint32_t flags, int *err); + int (*extents) (struct nbdkit_next_ops *next_ops, void *nxdata, + void *handle, uint32_t count, uint64_t offset, uint32_t flags, + struct nbdkit_extents_map *extents_map, + int *err); }; #define NBDKIT_REGISTER_FILTER(filter) \ diff --git a/include/nbdkit-plugin.h b/include/nbdkit-plugin.h index d43b2f5..76cec54 100644 --- a/include/nbdkit-plugin.h +++ b/include/nbdkit-plugin.h @@ -1,5 +1,5 @@ /* nbdkit - * Copyright (C) 2013-2018 Red Hat Inc. + * Copyright (C) 2013-2019 Red Hat Inc. * All rights reserved. * * Redistribution and use in source and binary forms, with or without @@ -125,6 +125,10 @@ struct nbdkit_plugin { const char *magic_config_key; int (*can_multi_conn) (void *handle); + + int (*can_extents) (void *handle); + int (*extents) (void *handle, uint32_t count, uint64_t offset, uint32_t flags, + struct nbdkit_extents_map *extents_map); }; extern void nbdkit_set_error (int err); diff --git a/server/internal.h b/server/internal.h index d40a82d..d0da213 100644 --- a/server/internal.h +++ b/server/internal.h @@ -274,6 +274,7 @@ struct backend { int (*is_rotational) (struct backend *, struct connection *conn); int (*can_trim) (struct backend *, struct connection *conn); int (*can_zero) (struct backend *, struct connection *conn); + int (*can_extents) (struct backend *, struct connection *conn); int (*can_fua) (struct backend *, struct connection *conn); int (*can_multi_conn) (struct backend *, struct connection *conn); @@ -287,6 +288,10 @@ struct backend { uint64_t offset, uint32_t flags, int *err); int (*zero) (struct backend *, struct connection *conn, uint32_t count, uint64_t offset, uint32_t flags, int *err); + int (*extents) (struct backend *, struct connection *conn, uint32_t count, + uint64_t offset, uint32_t flags, + struct nbdkit_extents_map *extents_map, + int *err); }; /* plugins.c */ diff --git a/server/extents.c b/server/extents.c new file mode 100644 index 0000000..f17ba05 --- /dev/null +++ b/server/extents.c @@ -0,0 +1,574 @@ +/* nbdkit + * Copyright (C) 2019 Red Hat Inc. + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are + * met: + * + * * Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * + * * Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * * Neither the name of Red Hat nor the names of its contributors may be + * used to endorse or promote products derived from this software without + * specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, + * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A + * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR + * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, + * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT + * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF + * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND + * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, + * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT + * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + +#include <config.h> + +#include <stdio.h> +#include <stdlib.h> +#include <stdint.h> +#include <stdbool.h> +#include <string.h> +#include <inttypes.h> +#include <assert.h> + +#include "minmax.h" + +#include "internal.h" + +/* Trivial implementation as an ordered list of extents. We will + * probably have to change this to a more efficient data structure if + * we have plugins with lots of extents. + * + * Invariants: + * - extents are stored in ascending order + * - extents must not overlap + * - adjacent extents must not have the same type + * + * Gaps are treated as type 0 (allocated data). + */ +struct nbdkit_extents_map { + struct extent *extents; + size_t nr_extents, allocated; +}; + +struct extent { + uint64_t offset; + uint64_t length; + uint32_t type; +}; + +struct nbdkit_extents_map * +nbdkit_extents_new (void) +{ + struct nbdkit_extents_map *r; + + r = malloc (sizeof *r); + if (r == NULL) { + nbdkit_error ("nbdkit_extents_new: malloc: %m"); + return NULL; + } + r->extents = NULL; + r->nr_extents = r->allocated = 0; + return r; +} + +void +nbdkit_extents_free (struct nbdkit_extents_map *map) +{ + if (map) { + free (map->extents); + free (map); + } +} + +static ssize_t +find_extent_recursive (const struct nbdkit_extents_map *map, + uint64_t offset, size_t first, size_t last) +{ + size_t i, h; + + assert (first <= last); + assert (offset >= map->extents[first].offset); + + if (last - first <= 8) { + /* Do a linear search for the last bit. */ + for (i = first+1; i <= last; ++i) { + if (offset < map->extents[i].offset) + return i-1; + } + return last; + } + + h = first + (last - first) / 2; + + if (offset < map->extents[h].offset) + return find_extent_recursive (map, offset, first, h-1); + else + return find_extent_recursive (map, offset, h, last); +} + +/* Find the extent before or containing offset. If offset is inside + * the extent, the extent index is returned. If offset is not in any + * extent, but there is an extent with a lower offset, then the index + * of the nearest lower extent is returned. If offset is before the + * zeroth extent then -1 is returned. + */ +static ssize_t +find_extent (const struct nbdkit_extents_map *map, uint64_t offset) +{ + if (map->nr_extents == 0 || offset < map->extents[0].offset) + return -1; + + return find_extent_recursive (map, offset, 0, map->nr_extents-1); +} + +/* Erase extents [i...i+count-1] from the array. Extents after are + * renumbered. + */ +static void +erase_extents (struct nbdkit_extents_map *map, + size_t i, size_t count) +{ + assert (i+count <= map->nr_extents); + + memmove (&map->extents[i], + &map->extents[i+count], + (map->nr_extents - (i+count)) * sizeof (struct extent)); + map->nr_extents -= count; +} + +/* Insert new_extent in the map at index i. Existing extents at index + * [i...] are moved up by one. + */ +static int +insert_extent (struct nbdkit_extents_map *map, + struct extent new_extent, size_t i) +{ + assert (i <= map->nr_extents); + + if (map->nr_extents >= map->allocated) { + size_t new_allocated; + struct extent *new_extents; + + new_allocated = map->allocated; + if (new_allocated == 0) + new_allocated = 1; + new_allocated *= 2; + new_extents = + realloc (map->extents, new_allocated * sizeof (struct extent)); + if (new_extents == NULL) { + nbdkit_error ("extent_add: realloc: %m"); + return -1; + } + map->allocated = new_allocated; + map->extents = new_extents; + } + + memmove (&map->extents[i+1], &map->extents[i], + (map->nr_extents - i) * sizeof (struct extent)); + map->nr_extents++; + map->extents[i] = new_extent; + return 0; +} + +int +nbdkit_extent_add (struct nbdkit_extents_map *map, + uint64_t offset, uint64_t length, uint32_t type) +{ + ssize_t lo, hi; + bool coalesce_below, coalesce_above; + struct extent new_extent; + + /* This might be considered an error, but be flexible for badly + * written plugins. + */ + if (length == 0) + return 0; + + /* Don't allow extents to exceeed the _signed_ 64 bit limit that is + * used in the rest of nbdkit. + */ + if (offset > INT64_MAX || + offset + length < offset || + offset + length > INT64_MAX) { + nbdkit_error ("nbdkit_extent_add: " + "extent cannot exceed signed 64 bit limit: " + "offset=%" PRIu64 " length=%" PRIu64, + offset, length); + return -1; + } + + again: + lo = find_extent (map, offset); + hi = find_extent (map, offset + length - 1); + + /* "lo" and "hi" are -1 or they point to the extent + * overlapping-or-below the corresponding endpoints of the new + * extent. + * + * The algorithm here has two parts: Firstly we remove any + * overlapping extents (this may involve erasing extents completely + * or shrinking them). Secondly we insert the new extent at the + * right place in the array, if necessary allowing it to coalesce + * with the extent above or below. + * + * To remove overlapping extents we consider 7 cases: + * + * A.0 lo == -1 (there is no old extent before the new extent) + * => do nothing + * + * A.1 ┌─────┐ offset of new extent exactly at + * │ lo │ beginning of lo and lo smaller/equal + * └─────┘ to new extent + * ↑ + * ▐▓▓▓▓▓▓▓▓▓ + * => erase lo + * => creates situation A.0 or A.5 + * + * A.2 ┌──────────┐ offset of new extent exactly at + * │ lo │ beginning of lo and lo bigger than + * └──────────┘ new extent + * ↑ + * ▐▓▓▓▓▓▓▓▓▓ + * => shrink lo “upwards” + * => creates situation A.0 or A.5 + * + * A.3 ┌──────────────┐ new extent in the middle + * │ lo │ of lo + * └──────────────┘ + * ↑ + * ▓▓▓▓▓▓▓▓▓ + * => split lo + * => creates situation A.5 + * + * A.4 ┌─────┐ offset of new extent in the middle + * │ lo │ of lo + * └─────┘ + * ↑ + * ▓▓▓▓▓▓▓▓▓ + * => shrink lo + * => creates situation A.5 + * + * A.5 ┌─────┐ offset of new extent after lo + * │ lo │ + * └─────┘ + * ↑ + * ▓▓▓▓▓▓▓▓▓ + * => do nothing + * + * B.0 lo == hi or hi == -1 (there is no higher extent) + * => do nothing + * + * B.1 ┌─────┐ extent hi is fully covered + * │ hi │ by new extent + * └─────┘ + * ↑ + * ▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓ + * => erase hi + * => creates situation B.0 + * + * B.2 ┌─────┐ extent hi is partly overlapped + * │ hi │ by new extent + * └─────┘ + * ↑ + * ▓▓▓▓▓▓▓▓▓▓▓ + * => shrink hi + * => creates situation B.0 + * + * In addition extents [lo+1...hi-1] (if they exist) are erased + * since they must be fully covered by the new extent. + * + * At the end we're in situation A.0/A.5 and B.0, and so no old + * extents overlap the new extent. + * + * The insertion can then be done with optional coalescing (see code + * below for details - this is a lot simpler). + */ + + /* A.0 */ + if (lo == -1) + goto erase_middle_extents; + /* A.5 */ + if (offset >= map->extents[lo].offset + map->extents[lo].length) + goto erase_middle_extents; + + /* A.1 or A.2 */ + if (offset == map->extents[lo].offset) { + if (map->extents[lo].offset + map->extents[lo].length <= offset + length) { + /* A.1 */ + erase_extents (map, lo, 1); + } + else { + /* A.2 */ + uint64_t end = map->extents[lo].offset + map->extents[lo].length; + map->extents[lo].offset = offset + length; + map->extents[lo].length = end - map->extents[lo].offset; + } + goto again; + } + + /* A.3 */ + if (map->extents[lo].offset < offset && + map->extents[lo].offset + map->extents[lo].length > offset + length) { + new_extent.offset = offset + length; + new_extent.length = + map->extents[lo].offset + map->extents[lo].length - new_extent.offset; + new_extent.type = map->extents[lo].type; + map->extents[lo].length = offset - map->extents[lo].offset; + if (insert_extent (map, new_extent, lo+1) == -1) + return -1; + goto again; + } + + /* We must be in situation A.4 assuming analysis above is exhaustive. */ + assert (offset > map->extents[lo].offset); + assert (offset < map->extents[lo].offset + map->extents[lo].length); + assert (map->extents[lo].offset + map->extents[lo].length <= offset + length); + + map->extents[lo].length = offset - map->extents[lo].offset; + + erase_middle_extents: + /* Erase extents [lo+1..hi-1] if they exist as they must be + * completely covered by the new extent. + */ + if (hi >= 0 && lo+1 < hi) { + erase_extents (map, lo+1, hi-lo-1); + goto again; + } + + /* B.0 */ + if (lo == hi || hi == -1) + goto insert; + + /* B.1 */ + if (map->extents[hi].offset + map->extents[hi].length <= offset + length) { + erase_extents (map, hi, 1); + goto again; + } + + /* We must be in situation B.2 if the analysis above is exhaustive. */ + assert (map->extents[hi].offset < offset + length); + + uint64_t end = map->extents[hi].offset + map->extents[hi].length; + map->extents[hi].offset = offset + length; + map->extents[hi].length = end - map->extents[hi].offset; + + insert: + /* Now we know there is no extent which overlaps with the new + * extent, and the new extent must be inserted after lo. + */ + + /* However we have to deal with possibly coalescing the new extent + * with lo and/or lo+1. + */ + coalesce_below = + lo >= 0 && + map->extents[lo].type == type && + map->extents[lo].offset + map->extents[lo].length == offset; + coalesce_above = + lo+1 < map->nr_extents && + map->extents[lo+1].type == type && + map->extents[lo+1].offset == offset + length; + + if (coalesce_below && coalesce_above) { + /* Coalesce lo + new extent + lo+1 + * => Extend lo to cover the whole range and remove lo+1. + */ + map->extents[lo].length = + map->extents[lo+1].offset + map->extents[lo+1].length + - map->extents[lo].offset; + erase_extents (map, lo+1, 1); + } + else if (coalesce_below) { + /* Coalesce lo + new extent. + * => Extend lo to cover new extent. + */ + map->extents[lo].length = offset + length - map->extents[lo].offset; + } + else if (coalesce_above) { + /* Coalesce new extent + lo+1 + * => Extend lo+1 to cover new extent. + */ + map->extents[lo+1].length = + map->extents[lo+1].offset + map->extents[lo+1].length - offset; + map->extents[lo+1].offset = offset; + } + else { + /* Normal case: Allocate a new extent and insert it after lo. */ + new_extent.offset = offset; + new_extent.length = length; + new_extent.type = type; + if (insert_extent (map, new_extent, lo+1) == -1) + return -1; + } + + return 0; +} + +int +nbdkit_extents_foreach (const struct nbdkit_extents_map *map, + nbdkit_extents_callback fn, void *opaque, + uint32_t flags, + uint64_t range_offset, uint64_t range_length) +{ + const bool flag_range = flags & NBDKIT_EXTENTS_FOREACH_FLAG_RANGE; + const bool flag_one = flags & NBDKIT_EXTENTS_FOREACH_FLAG_ONE; + uint64_t offset, next; + size_t i; + + if (flag_range) { + if (range_offset + range_length < range_offset) { + nbdkit_error ("nbdkit_extents_foreach: invalid range: " + "offset=%" PRIu64 " length=%" PRIu64, + range_offset, range_length); + return -1; + } + } + else { + range_offset = 0; + range_length = INT64_MAX + UINT64_C(1); + } + + for (i = 0, offset = range_offset; + offset < range_offset + range_length; + offset = next) { + next = offset; + + if (i >= map->nr_extents) { + /* Beyond last extent => Type 0 to end of range. */ + next = range_offset + range_length; + if (fn (offset, next - offset, 0, opaque) == -1) + return -1; + if (flag_one) + return 0; + continue; + } + + if (offset < map->extents[i].offset) { + /* In a gap before the i'th extent => Type 0 to next offset. */ + next = MIN (map->extents[i].offset, range_offset + range_length); + if (fn (offset, next - offset, 0, opaque) == -1) + return -1; + if (flag_one) + return 0; + continue; + } + + if (offset < map->extents[i].offset + map->extents[i].length) { + /* In an extent. */ + next = MIN (map->extents[i].offset + map->extents[i].length, + range_offset + range_length); + if (fn (offset, next - offset, map->extents[i].type, opaque) == -1) + return -1; + if (flag_one) + return 0; + continue; + } + + /* After an extent, increment i and iterate. */ + i++; + } + + return 0; +} + +#ifdef IN_TEST_EXTENTS +/* These functions are only compiled for and called from the unit tests. */ + +void +dump_extents_map (const struct nbdkit_extents_map *map) +{ + size_t i; + + fprintf (stderr, "map %p:\n", map); + fprintf (stderr, "\tnr_extents=%zu allocated=%zu\n", + map->nr_extents, map->allocated); + for (i = 0; i < map->nr_extents; ++i) { + fprintf (stderr, "\textent %zu:", i); + fprintf (stderr, + "\toffset=%" PRIu64 " length=%" PRIu64 " " + "last=%" PRIu64 " type=%" PRIu32 "\n", + map->extents[i].offset, map->extents[i].length, + map->extents[i].offset + map->extents[i].length - 1, + map->extents[i].type); + } +} + +void +validate_extents_map (const struct nbdkit_extents_map *map) +{ + size_t i; + bool fail = false; + + if (map->nr_extents > map->allocated) { + fprintf (stderr, "validate_extents_map: nr_extents > allocated\n"); + fail = true; + } + + for (i = 0; i < map->nr_extents; ++i) { + /* Extent length must be > 0. */ + if (map->extents[i].length == 0) { + fprintf (stderr, "validate_extents_map: %zu: extent length must be > 0\n", + i); + fail = true; + } + + /* Extent length must not wrap around, indicating that we have + * computed a negative length (as unsigned) somewhere. + */ + if (map->extents[i].offset + map->extents[i].length < + map->extents[i].offset) { + fprintf (stderr, "validate_extents_map: %zu: negative length\n", + i); + fail = true; + } + + if (i > 0) { + /* Extents are stored in strictly ascending order. */ + if (map->extents[i-1].offset >= map->extents[i].offset) { + fprintf (stderr, + "validate_extents_map: %zu: " + "not strictly ascending order\n", i); + fail = true; + } + + /* Adjacent extents must not overlap. */ + if (map->extents[i-1].offset + map->extents[i-1].length > + map->extents[i].offset) { + fprintf (stderr, + "validate_extents_map: %zu: " + "overlapping extents\n", i); + fail = true; + } + + /* Adjacent extents either have a different type or are + * separated by a gap. + */ + if (map->extents[i-1].type == map->extents[i].type && + map->extents[i-1].offset + map->extents[i-1].length == + map->extents[i].offset) { + fprintf (stderr, + "validate_extents_map: %zu: " + "adjacent extents with same type not coalesced\n", i); + fail = true; + } + } + } + + if (fail) { + dump_extents_map (map); + abort (); + } +} + +#endif /* IN_TEST_EXTENTS */ diff --git a/server/filters.c b/server/filters.c index 5b7abc4..e284080 100644 --- a/server/filters.c +++ b/server/filters.c @@ -309,6 +309,13 @@ next_can_zero (void *nxdata) return b_conn->b->can_zero (b_conn->b, b_conn->conn); } +static int +next_can_extents (void *nxdata) +{ + struct b_conn *b_conn = nxdata; + return b_conn->b->can_extents (b_conn->b, b_conn->conn); +} + static int next_can_fua (void *nxdata) { @@ -364,6 +371,16 @@ next_zero (void *nxdata, uint32_t count, uint64_t offset, uint32_t flags, return b_conn->b->zero (b_conn->b, b_conn->conn, count, offset, flags, err); } +static int +next_extents (void *nxdata, uint32_t count, uint64_t offset, uint32_t flags, + struct nbdkit_extents_map *extents_map, + int *err) +{ + struct b_conn *b_conn = nxdata; + return b_conn->b->extents (b_conn->b, b_conn->conn, count, offset, flags, + extents_map, err); +} + static struct nbdkit_next_ops next_ops = { .get_size = next_get_size, .can_write = next_can_write, @@ -371,6 +388,7 @@ static struct nbdkit_next_ops next_ops = { .is_rotational = next_is_rotational, .can_trim = next_can_trim, .can_zero = next_can_zero, + .can_extents = next_can_extents, .can_fua = next_can_fua, .can_multi_conn = next_can_multi_conn, .pread = next_pread, @@ -378,6 +396,7 @@ static struct nbdkit_next_ops next_ops = { .flush = next_flush, .trim = next_trim, .zero = next_zero, + .extents = next_extents, }; static int @@ -511,6 +530,21 @@ filter_can_zero (struct backend *b, struct connection *conn) return f->backend.next->can_zero (f->backend.next, conn); } +static int +filter_can_extents (struct backend *b, struct connection *conn) +{ + struct backend_filter *f = container_of (b, struct backend_filter, backend); + void *handle = connection_get_handle (conn, f->backend.i); + struct b_conn nxdata = { .b = f->backend.next, .conn = conn }; + + debug ("%s: can_extents", f->name); + + if (f->filter.can_extents) + return f->filter.can_extents (&next_ops, &nxdata, handle); + else + return f->backend.next->can_extents (f->backend.next, conn); +} + static int filter_can_fua (struct backend *b, struct connection *conn) { @@ -646,6 +680,31 @@ filter_zero (struct backend *b, struct connection *conn, count, offset, flags, err); } +static int +filter_extents (struct backend *b, struct connection *conn, + uint32_t count, uint64_t offset, uint32_t flags, + struct nbdkit_extents_map *extents_map, + int *err) +{ + struct backend_filter *f = container_of (b, struct backend_filter, backend); + void *handle = connection_get_handle (conn, f->backend.i); + struct b_conn nxdata = { .b = f->backend.next, .conn = conn }; + + assert (!(flags & ~NBDKIT_FLAG_REQ_ONE)); + + debug ("%s: extents count=%" PRIu32 " offset=%" PRIu64 " flags=0x%" PRIx32, + f->name, count, offset, flags); + + if (f->filter.extents) + return f->filter.extents (&next_ops, &nxdata, handle, + count, offset, flags, + extents_map, err); + else + return f->backend.next->extents (f->backend.next, conn, + count, offset, flags, + extents_map, err); +} + static struct backend filter_functions = { .free = filter_free, .thread_model = filter_thread_model, @@ -667,6 +726,7 @@ static struct backend filter_functions = { .is_rotational = filter_is_rotational, .can_trim = filter_can_trim, .can_zero = filter_can_zero, + .can_extents = filter_can_extents, .can_fua = filter_can_fua, .can_multi_conn = filter_can_multi_conn, .pread = filter_pread, @@ -674,6 +734,7 @@ static struct backend filter_functions = { .flush = filter_flush, .trim = filter_trim, .zero = filter_zero, + .extents = filter_extents, }; /* Register and load a filter. */ diff --git a/server/plugins.c b/server/plugins.c index 28b96ad..0bd523b 100644 --- a/server/plugins.c +++ b/server/plugins.c @@ -1,5 +1,5 @@ /* nbdkit - * Copyright (C) 2013-2018 Red Hat Inc. + * Copyright (C) 2013-2019 Red Hat Inc. * All rights reserved. * * Redistribution and use in source and binary forms, with or without @@ -199,6 +199,8 @@ plugin_dump_fields (struct backend *b) HAS (trim); HAS (zero); HAS (can_multi_conn); + HAS (can_extents); + HAS (extents); #undef HAS /* Custom fields. */ @@ -392,6 +394,21 @@ plugin_can_zero (struct backend *b, struct connection *conn) return plugin_can_write (b, conn); } +static int +plugin_can_extents (struct backend *b, struct connection *conn) +{ + struct backend_plugin *p = container_of (b, struct backend_plugin, backend); + + assert (connection_get_handle (conn, 0)); + + debug ("can_extents"); + + if (p->plugin.can_extents) + return p->plugin.can_extents (connection_get_handle (conn, 0)); + else + return p->plugin.extents != NULL; +} + static int plugin_can_fua (struct backend *b, struct connection *conn) { @@ -651,6 +668,41 @@ plugin_zero (struct backend *b, struct connection *conn, return r; } +static int +plugin_extents (struct backend *b, struct connection *conn, + uint32_t count, uint64_t offset, uint32_t flags, + struct nbdkit_extents_map *extents_map, + int *err) +{ + struct backend_plugin *p = container_of (b, struct backend_plugin, backend); + bool req_one = flags & NBDKIT_FLAG_REQ_ONE; + int r; + + assert (connection_get_handle (conn, 0)); + assert (!(flags & ~NBDKIT_FLAG_REQ_ONE)); + + debug ("extents count=%" PRIu32 " offset=%" PRIu64 " req_one=%d", + count, offset, req_one); + + if (!count) + return 0; + + if (p->plugin.extents) { + r = p->plugin.extents (connection_get_handle (conn, 0), count, offset, + flags, extents_map); + if (r == -1) + *err = get_error (p); + return r; + } + else { + /* By default we assume that everything in the range is allocated. + * However as that is the default state for the empty extents_map + * we don't need to do anything here. + */ + return 0; + } +} + static struct backend plugin_functions = { .free = plugin_free, .thread_model = plugin_thread_model, @@ -672,6 +724,7 @@ static struct backend plugin_functions = { .is_rotational = plugin_is_rotational, .can_trim = plugin_can_trim, .can_zero = plugin_can_zero, + .can_extents = plugin_can_extents, .can_fua = plugin_can_fua, .can_multi_conn = plugin_can_multi_conn, .pread = plugin_pread, @@ -679,6 +732,7 @@ static struct backend plugin_functions = { .flush = plugin_flush, .trim = plugin_trim, .zero = plugin_zero, + .extents = plugin_extents, }; /* Register and load a plugin. */ diff --git a/server/test-extents.c b/server/test-extents.c new file mode 100644 index 0000000..e07ecda --- /dev/null +++ b/server/test-extents.c @@ -0,0 +1,151 @@ +/* nbdkit + * Copyright (C) 2018-2019 Red Hat Inc. + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are + * met: + * + * * Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * + * * Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * * Neither the name of Red Hat nor the names of its contributors may be + * used to endorse or promote products derived from this software without + * specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, + * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A + * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR + * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, + * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT + * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF + * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND + * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, + * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT + * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + +/* Test the extents handling code (server/extents.c). This stochastic + * test works by allocating an array representing a disk, allocating + * extents randomly while writing the same information into the disk + * array, and then reading the extents back and comparing it to what's + * in the disk array. + */ + +#include <config.h> + +#include <stdio.h> +#include <stdlib.h> +#include <stdbool.h> +#include <inttypes.h> +#include <time.h> +#include <assert.h> + +#include "minmax.h" +#include "random.h" + +#include "internal.h" + +extern void dump_extents_map (const struct nbdkit_extents_map *map); +extern void validate_extents_map (const struct nbdkit_extents_map *map); + +#define DISK_SIZE (1<<10) +static uint8_t disk[DISK_SIZE]; + +static bool error_flagged = false; + +/* Stub for linking against server/extents.c. */ +void +nbdkit_error (const char *fs, ...) +{ + error_flagged = true; +} + +static int +compare (uint64_t offset, uint64_t length, uint32_t type, void *mapv) +{ + const struct nbdkit_extents_map *map = mapv; + size_t j; + + /* nbdkit_extents_foreach_range should ensure this is true even if + * there are extents which go below or above the range. + */ + assert (offset >= 0); + assert (offset + length <= DISK_SIZE); + + fprintf (stderr, + "compare: offset=%" PRIu64 " length=%" PRIu64 " " + "type=%" PRIu32 "\n", + offset, length, type); + + for (j = offset; j < offset+length; ++j) { + if (disk[j] != type) { + fprintf (stderr, "error: disk[%zu] != expected type %" PRIu32 "\n", + j, type); + dump_extents_map (map); + exit (EXIT_FAILURE); + } + } + + return 0; +} + +int +main (int argc, char *argv[]) +{ + unsigned i; + uint64_t offset, length; + uint32_t type; + size_t j; + struct random_state random_state; + struct nbdkit_extents_map *map; + + xsrandom (time (NULL), &random_state); + + map = nbdkit_extents_new (); + assert (map != NULL); + + for (i = 0; i < 1000; ++i) { + type = xrandom (&random_state); + type &= 3; + offset = xrandom (&random_state); + offset &= DISK_SIZE - 1; + /* XXX Change the distribution so we mainly choose small lengths + * but with a small possibility of choosing large lengths. + */ + length = xrandom (&random_state); + length &= DISK_SIZE/8 - 1; + length++; + + fprintf (stderr, + "insert: extent offset=%" PRIu64 " length=%" PRIu64 " " + "type=%" PRIu32 "\n", + offset, length, type); + + assert (nbdkit_extent_add (map, offset, length, type) == 0); + + for (j = offset; j < MIN (offset+length, DISK_SIZE); ++j) + disk[j] = type; + + /* Ask the extents code to validate that the invariants are still + * true. This calls abort(3) if not. + */ + validate_extents_map (map); + dump_extents_map (map); + } + + /* Read out the extents and compare them to the disk. */ + assert (nbdkit_extents_foreach (map, compare, map, + NBDKIT_EXTENTS_FOREACH_FLAG_RANGE, + 0, DISK_SIZE-1) == 0); + + nbdkit_extents_free (map); + + exit (EXIT_SUCCESS); +} diff --git a/.gitignore b/.gitignore index dc42abd..1f8b2e0 100644 --- a/.gitignore +++ b/.gitignore @@ -63,6 +63,7 @@ Makefile.in /server/nbdkit.pc /server/protostrings.c /server/synopsis.c +/server/test-extents /server/test-utils /stamp-h1 /tests/disk diff --git a/server/Makefile.am b/server/Makefile.am index 5eb575e..5722f7b 100644 --- a/server/Makefile.am +++ b/server/Makefile.am @@ -43,6 +43,7 @@ nbdkit_SOURCES = \ connections.c \ crypto.c \ debug.c \ + extents.c \ filters.c \ internal.h \ locks.c \ @@ -129,9 +130,22 @@ pkgconfig_DATA = nbdkit.pc # Unit testing -TESTS = test-utils +TESTS = \ + test-extents \ + test-utils -check_PROGRAMS = test-utils +check_PROGRAMS = \ + test-extents \ + test-utils + +test_extents_SOURCES = \ + test-extents.c \ + extents.c +test_extents_CPPFLAGS = \ + -DIN_TEST_EXTENTS=1 \ + -I$(top_srcdir)/include \ + -I$(top_srcdir)/common/include +test_extents_CFLAGS = $(WARNINGS_CFLAGS) $(VALGRIND_CFLAGS) test_utils_SOURCES = \ test-utils.c \ -- 2.20.1

On 3/19/19 11:34 AM, Richard W.M. Jones wrote: Resuming where I left off, if it helps: Worth using fixed-width formatting so that consecutive lines are tabular, and/or using hex offsets (in addition to decimal) for easier spotting of alignments? Of course, if we failed the previous check, this now reads beyond the end of the allocation. But it's debug code. No validation that extents don't exceed INT64_MAX? This changes if you don't allow gaps (it does sound like the implementation will be easier if it is gap-free...) For now, should we default filter.can_extents to false until we completed the work for all filters? Dead assertion (always true since offset is unsigned). The test is rendered less powerful when NDEBUG is defined. But it doesn't affect production code (and maybe we could ensure that this file #undef NDEBUG regardless of what the user decides via -D for assertions in the overall project) -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org

On 3/19/19 11:35 AM, Richard W.M. Jones wrote: The NBD protocol recommends that context_id for replies to OPT_LIST_META_CONTEXT be set to 0, but requires the client to ignore the context_id. Here, you are blindly returning a context_id of 1 regardless of _LIST or _SET. Hmm. For NBD_CMD_WRITE_ZEROES, we decided that in the common case, .can_zero would default to true for plugins even when the plugin lacks .zero (on the grounds that always advertising it to the client allows for less network traffic, even if nbdkit has to do the fallback) (see commits 7ac98831, bde4fc4). We then added the nozero filter to specifically disable the advertisement as needed. This seems like another case where we should advertise the feature by default (even when the plugin lacks .extents) on the grounds that a client might benefit from knowing that an image can't report sparseness, then provide a filter comparable to nozero that fine-tunes what we actually advertise. But I don't think that fine-tuning affects this patch (which looks right to me to just query .can_extents), but rather what we default to in patch 1 for plugins (I also argued that defaulting filters to default to false until we've audited all filters may be wise). If you take my suggestion of an END type, I think that foreach() should still iterate over any extent marked END, but count_extents should not count it. Or maybe foreach gains a flag for whether the caller is interested in visiting END extents or just stopping right away when one is encountered (filters would be interested, while this code is probably not). If we pre-populate a map with data over the client's initial range and with END beyond the range, it is conceivable that a client will slam the end of the file to be a data extent which will then coalesce to something larger than 32 bits. But we can also be clever and call nbd_extents_add(offset + UINT32_MAX, END) after calling into the client prior to calling foreach to keep this assertion true, even if we want to support the NBD protocol's ability for the last extent (when no REQ_ONE flag) to advertise a length longer that the client's request. You probably ought to return an error if nr_blocks is 0 (possible if a client registered an END type immediately on offset), as the NBD spec requires a successful call to make progress. Hmm. We probably ought to cap the number of extents we are willing to send to avoid an over-long reply. Since we reject NBD_CMD_READ calls requesting more than 64M of data, we probably also ought to guarantee a truncated reply if it would otherwise generate more than 64M of extent information in the reply (or maybe pick a smaller limit, maybe 1M?). Each extent block is 64 bytes, so capping at 1M blocks would be a 64M reply; a lower cap of 64k blocks or even 1k blocks would still be reasonable. Looks good. May need tweaking if you like my idea of having _new() take the client's initial bounds as parameters. Correct observations; permitting arbitrary metadata contexts will indeed be a much more interesting addition, if we ever decide to do so. -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org

On 3/19/19 11:35 AM, Richard W.M. Jones wrote: Squash this into 1? -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org

These plugins are both based on the same sparse array structure which supports a simple implementation of extents. --- common/sparse/sparse.h | 7 ++++++- common/sparse/sparse.c | 29 ++++++++++++++++++++++++++++- plugins/data/data.c | 16 +++++++++++++++- plugins/memory/memory.c | 16 +++++++++++++++- 4 files changed, 64 insertions(+), 4 deletions(-) diff --git a/common/sparse/sparse.h b/common/sparse/sparse.h index 818d804..23e31b9 100644 --- a/common/sparse/sparse.h +++ b/common/sparse/sparse.h @@ -1,5 +1,5 @@ /* nbdkit - * Copyright (C) 2017-2018 Red Hat Inc. + * Copyright (C) 2017-2019 Red Hat Inc. * All rights reserved. * * Redistribution and use in source and binary forms, with or without @@ -87,4 +87,9 @@ extern void sparse_array_zero (struct sparse_array *sa, uint32_t count, uint64_t offset) __attribute__((__nonnull__ (1))); +/* Return information about allocated pages and holes. */ +extern int sparse_array_extents (struct sparse_array *sa, + uint32_t count, uint64_t offset, + struct nbdkit_extents_map *extents_map); + #endif /* NBDKIT_SPARSE_H */ diff --git a/common/sparse/sparse.c b/common/sparse/sparse.c index a5ace48..56bfa77 100644 --- a/common/sparse/sparse.c +++ b/common/sparse/sparse.c @@ -1,5 +1,5 @@ /* nbdkit - * Copyright (C) 2017-2018 Red Hat Inc. + * Copyright (C) 2017-2019 Red Hat Inc. * All rights reserved. * * Redistribution and use in source and binary forms, with or without @@ -360,3 +360,30 @@ sparse_array_zero (struct sparse_array *sa, uint32_t count, uint64_t offset) offset += n; } } + +int +sparse_array_extents (struct sparse_array *sa, + uint32_t count, uint64_t offset, + struct nbdkit_extents_map *extents_map) +{ + uint32_t n, type; + void *p; + + while (count > 0) { + p = lookup (sa, offset, false, &n, NULL); + if (n > count) + n = count; + + if (p == NULL) + type = NBDKIT_EXTENT_HOLE | NBDKIT_EXTENT_ZERO; + else + type = 0; /* allocated data */ + if (nbdkit_extent_add (extents_map, offset, n, type) == -1) + return -1; + + count -= n; + offset += n; + } + + return 0; +} diff --git a/plugins/data/data.c b/plugins/data/data.c index f9d3881..d580805 100644 --- a/plugins/data/data.c +++ b/plugins/data/data.c @@ -1,5 +1,5 @@ /* nbdkit - * Copyright (C) 2018 Red Hat Inc. + * Copyright (C) 2018-2019 Red Hat Inc. * All rights reserved. * * Redistribution and use in source and binary forms, with or without @@ -378,6 +378,19 @@ data_trim (void *handle, uint32_t count, uint64_t offset) return 0; } +/* Extents. */ +static int +data_extents (void *handle, uint32_t count, uint64_t offset, + uint32_t flags, struct nbdkit_extents_map *extents_map) +{ + int r; + + pthread_mutex_lock (&lock); + r = sparse_array_extents (sa, count, offset, extents_map); + pthread_mutex_unlock (&lock); + return r; +} + static struct nbdkit_plugin plugin = { .name = "data", .version = PACKAGE_VERSION, @@ -394,6 +407,7 @@ static struct nbdkit_plugin plugin = { .pwrite = data_pwrite, .zero = data_zero, .trim = data_trim, + .extents = data_extents, /* In this plugin, errno is preserved properly along error return * paths from failed system calls. */ diff --git a/plugins/memory/memory.c b/plugins/memory/memory.c index e27e127..fa09a35 100644 --- a/plugins/memory/memory.c +++ b/plugins/memory/memory.c @@ -1,5 +1,5 @@ /* nbdkit - * Copyright (C) 2017-2018 Red Hat Inc. + * Copyright (C) 2017-2019 Red Hat Inc. * All rights reserved. * * Redistribution and use in source and binary forms, with or without @@ -170,6 +170,19 @@ memory_trim (void *handle, uint32_t count, uint64_t offset) return 0; } +/* Extents. */ +static int +memory_extents (void *handle, uint32_t count, uint64_t offset, + uint32_t flags, struct nbdkit_extents_map *extents_map) +{ + int r; + + pthread_mutex_lock (&lock); + r = sparse_array_extents (sa, count, offset, extents_map); + pthread_mutex_unlock (&lock); + return r; +} + static struct nbdkit_plugin plugin = { .name = "memory", .version = PACKAGE_VERSION, @@ -185,6 +198,7 @@ static struct nbdkit_plugin plugin = { .pwrite = memory_pwrite, .zero = memory_zero, .trim = memory_trim, + .extents = memory_extents, /* In this plugin, errno is preserved properly along error return * paths from failed system calls. */ -- 2.20.1

This uses lseek SEEK_DATA/SEEK_HOLE to search for allocated data and holes in the underlying file. --- plugins/file/file.c | 142 ++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 132 insertions(+), 10 deletions(-) diff --git a/plugins/file/file.c b/plugins/file/file.c index 628f8fb..704deaa 100644 --- a/plugins/file/file.c +++ b/plugins/file/file.c @@ -1,5 +1,5 @@ /* nbdkit - * Copyright (C) 2013-2018 Red Hat Inc. + * Copyright (C) 2013-2019 Red Hat Inc. * All rights reserved. * * Redistribution and use in source and binary forms, with or without @@ -37,6 +37,7 @@ #include <stdlib.h> #include <stdbool.h> #include <string.h> +#include <inttypes.h> #include <fcntl.h> #include <unistd.h> #include <sys/types.h> @@ -44,6 +45,8 @@ #include <sys/ioctl.h> #include <errno.h> +#include <pthread.h> + #if defined(__linux__) && !defined(FALLOC_FL_PUNCH_HOLE) #include <linux/falloc.h> /* For FALLOC_FL_*, glibc < 2.18 */ #endif @@ -68,7 +71,11 @@ static char *filename = NULL; -int file_debug_zero; /* to enable: -D file.zero=1 */ +/* Any callbacks using lseek must be protected by this lock. */ +static pthread_mutex_t lseek_lock = PTHREAD_MUTEX_INITIALIZER; + +/* to enable: -D file.zero=1 */ +int file_debug_zero; static void file_unload (void) @@ -220,6 +227,21 @@ file_close (void *handle) #define THREAD_MODEL NBDKIT_THREAD_MODEL_PARALLEL +/* For block devices, stat->st_size is not the true size. */ +static int64_t +block_device_size (int fd) +{ + off_t size; + + size = lseek (fd, 0, SEEK_END); + if (size == -1) { + nbdkit_error ("lseek (to find device size): %m"); + return -1; + } + + return size; +} + /* Get the file size. */ static int64_t file_get_size (void *handle) @@ -227,15 +249,11 @@ file_get_size (void *handle) struct handle *h = handle; if (h->is_block_device) { - /* Block device, so st_size will not be the true size. */ - off_t size; - - size = lseek (h->fd, 0, SEEK_END); - if (size == -1) { - nbdkit_error ("lseek (to find device size): %m"); - return -1; - } + int64_t size; + pthread_mutex_lock (&lseek_lock); + size = block_device_size (h->fd); + pthread_mutex_unlock (&lseek_lock); return size; } else { /* Regular file. */ @@ -501,6 +519,106 @@ file_trim (void *handle, uint32_t count, uint64_t offset, uint32_t flags) return 0; } +#ifdef SEEK_HOLE +/* Extents. */ + +static int +file_can_extents (void *handle) +{ + struct handle *h = handle; + off_t r; + + /* A simple test to see whether SEEK_HOLE etc is likely to work on + * the current filesystem. + */ + pthread_mutex_lock (&lseek_lock); + r = lseek (h->fd, 0, SEEK_HOLE); + pthread_mutex_unlock (&lseek_lock); + if (r == -1) { + nbdkit_debug ("extents disabled: lseek: SEEK_HOLE: %m"); + return 0; + } + return 1; +} + +static int +do_extents (void *handle, uint32_t count, uint64_t offset, + uint32_t flags, struct nbdkit_extents_map *extents_map) +{ + struct handle *h = handle; + const bool req_one = flags & NBDKIT_FLAG_REQ_ONE; + size_t nr_extents = 0; + uint64_t end = offset + count; + + do { + off_t pos; + + pos = lseek (h->fd, offset, SEEK_DATA); + if (pos == -1) { + if (errno == ENXIO) { + /* The current man page does not describe this situation well, + * but a proposed change to POSIX adds these words for ENXIO: + * "or the whence argument is SEEK_DATA and the offset falls + * within the final hole of the file." + */ + pos = end; + } + else { + nbdkit_error ("lseek: SEEK_DATA: %" PRIu64 ": %m", offset); + return -1; + } + } + + /* We know there is a hole from offset to pos-1. */ + if (pos > offset) { + if (nbdkit_extent_add (extents_map, offset, pos - offset, + NBDKIT_EXTENT_HOLE | NBDKIT_EXTENT_ZERO) == -1) + return -1; + nr_extents++; + } + + offset = pos; + if (offset >= end) + break; + + pos = lseek (h->fd, offset, SEEK_HOLE); + if (pos == -1) { + nbdkit_error ("lseek: SEEK_HOLE: %" PRIu64 ": %m", offset); + return -1; + } + + /* We know there is data from offset to pos-1, but we don't have + * to add this to the map because that is the default. + */ + if (pos > offset) + nr_extents++; + + offset = pos; + + /* If the req_one flag is set, we must want until TWO extents have + * been added so that we have the limit of the first extent. + */ + if (req_one && nr_extents >= 2) + break; + } while (offset < end); + + return 0; +} + +static int +file_extents (void *handle, uint32_t count, uint64_t offset, + uint32_t flags, struct nbdkit_extents_map *extents_map) +{ + int r; + + pthread_mutex_lock (&lseek_lock); + r = do_extents (handle, count, offset, flags, extents_map); + pthread_mutex_unlock (&lseek_lock); + + return r; +} +#endif /* SEEK_HOLE */ + static struct nbdkit_plugin plugin = { .name = "file", .longname = "nbdkit file plugin", @@ -522,6 +640,10 @@ static struct nbdkit_plugin plugin = { .flush = file_flush, .trim = file_trim, .zero = file_zero, +#ifdef SEEK_HOLE + .can_extents = file_can_extents, + .extents = file_extents, +#endif .errno_is_preserved = 1, }; -- 2.20.1