Re: [PATCH 0/4] Userspace support for FSID change
On 2018/9/2 下午5:56, Nikolay Borisov wrote: > > > On 29.08.2018 15:47, Qu Wenruo wrote: >> >> >> On 2018/8/29 下午8:33, Nikolay Borisov wrote: >>> >>> >>> On 29.08.2018 15:09, Qu Wenruo wrote: On 2018/8/29 下午4:35, Nikolay Borisov wrote: > Here is the userspace tooling support for utilising the new metadata_uuid > field, > enabling the change of fsid without having to rewrite every metadata > block. This > patchset consists of adding support for the new field to various tools > and > files (Patch 1). The actual implementation of the new -m|-M options > (which are > described in more detail in Patch 2). A new misc-tests testcasei (Patch > 3) which > exercises the new options and verifies certain invariants hold (these are > also > described in Patch2). Patch 4 is more or less copy of the kernel > conuterpart > just reducing some duplication between btrfs_fs_info and btrfs_fs_devices > structures. So to my understand, now we have another layer of UUID. Before we have one fsid, both used in superblock and tree blocks. Now we have 2 fsid, the one used in tree blocks are kept the same, but changed its name to metadata_uuid in superblock. And superblock::fsid will become a new field, and although they are the same at mkfs time, they could change several times during its operation. This indeed makes uuid change super fast, only needs to update all superblocks of the fs, instead of all tree blocks. However I have one nitpick of the design. Unlike XFS, btrfs supports multiple devices. If we have a raid10 fs with 4 devices, and it has already gone through several UUID change (so its metadata uuid is already different from fsid). And during another UUID change procedure, we lost power while only updated 2 super blocks, what will happen for kernel device assembly? (Although considering how fast the UUID change would happen, such case should be super niche) >>> >>> Then I guess you will be fucked. I'm all ears for suggestion how to >>> rectify this without skyrocketing the complexity. The current UUID >>> rewrite method sets a flag int he superblock that FSID change is in >>> progress and clears it once every metadatablock has been rewritten. I >>> can piggyback on this mechanism but I'm not sure it provides 100% >>> guarantee. Because by the some token you can set this flag, start >>> writing the super blocks then lose power and then only some of the >>> superblocks could have this flag set so we back at square 1. >> >> Well, forget it, considering how fast the new method is, such case >> should be really rare. >> >>> > > The intended usecase of this feature is to give the sysadmin the ability > to > create copies of filesystesm, change their uuid quickly and mount them > alongside > the original filesystem for, say, forensic purposes. > > One thing which still hasn't been set in stone is whether the new options > will remain as -m|-M or whether they should subsume the current -u|-U - > from > the point of view of users nothing should change. Well, user would be surprised by how fast the new -m is, thus there is still something changed :) I prefer to subsume current -u/-U, and use the new one if the incompat feature is already set. Or fall back to original behavior. But I'm not a fan of using INCOMPAT flags as an indicator of changed fsid/metadata uuid. INCOMPAT feature should not change so easily nor acts as an indicator. That's to say, the flag should only be set at mkfs time, and then never change unlike the 2nd patch (I don't even like btrfstune to change incompat flags). E.g. mkfs.btrfs -O metadata_uuid , then we could use the new way to change fsid without touching metadata uuid. Or we could only use the old method. >>> >>> I disagree, I don't see any benefit in this but only added complexity. >>> Can you elaborate more ? >> >> Well, the incompat feature is really introducing some incompatible >> on-disk format change. >> So if you're introducing the new metadata_uuid field, no matter if it >> differs from fsid or not, it's a new field, and the incompat flag should >> be set. >> >> To me, older kernel could recognize the new format when fsid matches >> metadata uuid (since there in your current patchset, such case will not >> have incompat flag set) is a little dangerous. >> >> What will happen if such old kernel/btrfs-progs tries to change fsid? >> Older btrfs-progs doesn't know there is a new field, it will not touch >> the metadata uuid field, just changing the fsid field along with all >> tree blocks. >> >> This will cause a fs whose fsid doesn't match metadata uuid and has no >> incompat flag set. This is definitely leading to compatibility problem. > >
Re: [PATCH 0/4] Userspace support for FSID change
On 29.08.2018 15:47, Qu Wenruo wrote: > > > On 2018/8/29 下午8:33, Nikolay Borisov wrote: >> >> >> On 29.08.2018 15:09, Qu Wenruo wrote: >>> >>> >>> On 2018/8/29 下午4:35, Nikolay Borisov wrote: Here is the userspace tooling support for utilising the new metadata_uuid field, enabling the change of fsid without having to rewrite every metadata block. This patchset consists of adding support for the new field to various tools and files (Patch 1). The actual implementation of the new -m|-M options (which are described in more detail in Patch 2). A new misc-tests testcasei (Patch 3) which exercises the new options and verifies certain invariants hold (these are also described in Patch2). Patch 4 is more or less copy of the kernel conuterpart just reducing some duplication between btrfs_fs_info and btrfs_fs_devices structures. >>> >>> So to my understand, now we have another layer of UUID. >>> >>> Before we have one fsid, both used in superblock and tree blocks. >>> >>> Now we have 2 fsid, the one used in tree blocks are kept the same, but >>> changed its name to metadata_uuid in superblock. >>> And superblock::fsid will become a new field, and although they are the >>> same at mkfs time, they could change several times during its operation. >>> >>> This indeed makes uuid change super fast, only needs to update all >>> superblocks of the fs, instead of all tree blocks. >>> >>> However I have one nitpick of the design. Unlike XFS, btrfs supports >>> multiple devices. >>> If we have a raid10 fs with 4 devices, and it has already gone through >>> several UUID change (so its metadata uuid is already different from fsid). >>> >>> And during another UUID change procedure, we lost power while only >>> updated 2 super blocks, what will happen for kernel device assembly? >>> >>> (Although considering how fast the UUID change would happen, such case >>> should be super niche) >> >> Then I guess you will be fucked. I'm all ears for suggestion how to >> rectify this without skyrocketing the complexity. The current UUID >> rewrite method sets a flag int he superblock that FSID change is in >> progress and clears it once every metadatablock has been rewritten. I >> can piggyback on this mechanism but I'm not sure it provides 100% >> guarantee. Because by the some token you can set this flag, start >> writing the super blocks then lose power and then only some of the >> superblocks could have this flag set so we back at square 1. > > Well, forget it, considering how fast the new method is, such case > should be really rare. > >> >>> The intended usecase of this feature is to give the sysadmin the ability to create copies of filesystesm, change their uuid quickly and mount them alongside the original filesystem for, say, forensic purposes. One thing which still hasn't been set in stone is whether the new options will remain as -m|-M or whether they should subsume the current -u|-U - from the point of view of users nothing should change. >>> >>> Well, user would be surprised by how fast the new -m is, thus there is >>> still something changed :) >>> >>> I prefer to subsume current -u/-U, and use the new one if the incompat >>> feature is already set. Or fall back to original behavior. >>> >>> But I'm not a fan of using INCOMPAT flags as an indicator of changed >>> fsid/metadata uuid. >>> INCOMPAT feature should not change so easily nor acts as an indicator. >>> >>> That's to say, the flag should only be set at mkfs time, and then never >>> change unlike the 2nd patch (I don't even like btrfstune to change >>> incompat flags). >>> >>> E.g. >>> mkfs.btrfs -O metadata_uuid , then we could use the new way to >>> change fsid without touching metadata uuid. >>> Or we could only use the old method. >> >> I disagree, I don't see any benefit in this but only added complexity. >> Can you elaborate more ? > > Well, the incompat feature is really introducing some incompatible > on-disk format change. > So if you're introducing the new metadata_uuid field, no matter if it > differs from fsid or not, it's a new field, and the incompat flag should > be set. > > To me, older kernel could recognize the new format when fsid matches > metadata uuid (since there in your current patchset, such case will not > have incompat flag set) is a little dangerous. > > What will happen if such old kernel/btrfs-progs tries to change fsid? > Older btrfs-progs doesn't know there is a new field, it will not touch > the metadata uuid field, just changing the fsid field along with all > tree blocks. > > This will cause a fs whose fsid doesn't match metadata uuid and has no > incompat flag set. This is definitely leading to compatibility problem. Nope, when both fsid/metadata_uuid match and the INCOMPAT flag is not set then on-disk we never save the metadata_uuid value and this value is set only in-memory, the
Re: [PATCH 0/4] Userspace support for FSID change
On 2018/8/29 下午8:33, Nikolay Borisov wrote: > > > On 29.08.2018 15:09, Qu Wenruo wrote: >> >> >> On 2018/8/29 下午4:35, Nikolay Borisov wrote: >>> Here is the userspace tooling support for utilising the new metadata_uuid >>> field, >>> enabling the change of fsid without having to rewrite every metadata block. >>> This >>> patchset consists of adding support for the new field to various tools and >>> files (Patch 1). The actual implementation of the new -m|-M options (which >>> are >>> described in more detail in Patch 2). A new misc-tests testcasei (Patch 3) >>> which >>> exercises the new options and verifies certain invariants hold (these are >>> also >>> described in Patch2). Patch 4 is more or less copy of the kernel >>> conuterpart >>> just reducing some duplication between btrfs_fs_info and btrfs_fs_devices >>> structures. >> >> So to my understand, now we have another layer of UUID. >> >> Before we have one fsid, both used in superblock and tree blocks. >> >> Now we have 2 fsid, the one used in tree blocks are kept the same, but >> changed its name to metadata_uuid in superblock. >> And superblock::fsid will become a new field, and although they are the >> same at mkfs time, they could change several times during its operation. >> >> This indeed makes uuid change super fast, only needs to update all >> superblocks of the fs, instead of all tree blocks. >> >> However I have one nitpick of the design. Unlike XFS, btrfs supports >> multiple devices. >> If we have a raid10 fs with 4 devices, and it has already gone through >> several UUID change (so its metadata uuid is already different from fsid). >> >> And during another UUID change procedure, we lost power while only >> updated 2 super blocks, what will happen for kernel device assembly? >> >> (Although considering how fast the UUID change would happen, such case >> should be super niche) > > Then I guess you will be fucked. I'm all ears for suggestion how to > rectify this without skyrocketing the complexity. The current UUID > rewrite method sets a flag int he superblock that FSID change is in > progress and clears it once every metadatablock has been rewritten. I > can piggyback on this mechanism but I'm not sure it provides 100% > guarantee. Because by the some token you can set this flag, start > writing the super blocks then lose power and then only some of the > superblocks could have this flag set so we back at square 1. Well, forget it, considering how fast the new method is, such case should be really rare. > >> >>> >>> The intended usecase of this feature is to give the sysadmin the ability to >>> create copies of filesystesm, change their uuid quickly and mount them >>> alongside >>> the original filesystem for, say, forensic purposes. >>> >>> One thing which still hasn't been set in stone is whether the new options >>> will remain as -m|-M or whether they should subsume the current -u|-U - >>> from >>> the point of view of users nothing should change. >> >> Well, user would be surprised by how fast the new -m is, thus there is >> still something changed :) >> >> I prefer to subsume current -u/-U, and use the new one if the incompat >> feature is already set. Or fall back to original behavior. >> >> But I'm not a fan of using INCOMPAT flags as an indicator of changed >> fsid/metadata uuid. >> INCOMPAT feature should not change so easily nor acts as an indicator. >> >> That's to say, the flag should only be set at mkfs time, and then never >> change unlike the 2nd patch (I don't even like btrfstune to change >> incompat flags). >> >> E.g. >> mkfs.btrfs -O metadata_uuid , then we could use the new way to >> change fsid without touching metadata uuid. >> Or we could only use the old method. > > I disagree, I don't see any benefit in this but only added complexity. > Can you elaborate more ? Well, the incompat feature is really introducing some incompatible on-disk format change. So if you're introducing the new metadata_uuid field, no matter if it differs from fsid or not, it's a new field, and the incompat flag should be set. To me, older kernel could recognize the new format when fsid matches metadata uuid (since there in your current patchset, such case will not have incompat flag set) is a little dangerous. What will happen if such old kernel/btrfs-progs tries to change fsid? Older btrfs-progs doesn't know there is a new field, it will not touch the metadata uuid field, just changing the fsid field along with all tree blocks. This will cause a fs whose fsid doesn't match metadata uuid and has no incompat flag set. This is definitely leading to compatibility problem. So we need to follow the incompat flags rule strictly, if on-disk format is changed, we need the new incompat flag. Thanks, Qu > > >> >> Thanks, >> Qu >> >>> So this is something which >>> I'd like to hear from the community. Of course the alternative of rewriting >>> the metadata blocks will be assigne new options - perhaps -m|M ? >>>
Re: [PATCH 0/4] Userspace support for FSID change
On 2018-08-29 08:33, Nikolay Borisov wrote: On 29.08.2018 15:09, Qu Wenruo wrote: On 2018/8/29 下午4:35, Nikolay Borisov wrote: Here is the userspace tooling support for utilising the new metadata_uuid field, enabling the change of fsid without having to rewrite every metadata block. This patchset consists of adding support for the new field to various tools and files (Patch 1). The actual implementation of the new -m|-M options (which are described in more detail in Patch 2). A new misc-tests testcasei (Patch 3) which exercises the new options and verifies certain invariants hold (these are also described in Patch2). Patch 4 is more or less copy of the kernel conuterpart just reducing some duplication between btrfs_fs_info and btrfs_fs_devices structures. So to my understand, now we have another layer of UUID. Before we have one fsid, both used in superblock and tree blocks. Now we have 2 fsid, the one used in tree blocks are kept the same, but changed its name to metadata_uuid in superblock. And superblock::fsid will become a new field, and although they are the same at mkfs time, they could change several times during its operation. This indeed makes uuid change super fast, only needs to update all superblocks of the fs, instead of all tree blocks. However I have one nitpick of the design. Unlike XFS, btrfs supports multiple devices. If we have a raid10 fs with 4 devices, and it has already gone through several UUID change (so its metadata uuid is already different from fsid). And during another UUID change procedure, we lost power while only updated 2 super blocks, what will happen for kernel device assembly? (Although considering how fast the UUID change would happen, such case should be super niche) Then I guess you will be fucked. I'm all ears for suggestion how to rectify this without skyrocketing the complexity. The current UUID rewrite method sets a flag int he superblock that FSID change is in progress and clears it once every metadatablock has been rewritten. I can piggyback on this mechanism but I'm not sure it provides 100% guarantee. Because by the some token you can set this flag, start writing the super blocks then lose power and then only some of the superblocks could have this flag set so we back at square 1. The intended usecase of this feature is to give the sysadmin the ability to create copies of filesystesm, change their uuid quickly and mount them alongside the original filesystem for, say, forensic purposes. One thing which still hasn't been set in stone is whether the new options will remain as -m|-M or whether they should subsume the current -u|-U - from the point of view of users nothing should change. Well, user would be surprised by how fast the new -m is, thus there is still something changed :) I prefer to subsume current -u/-U, and use the new one if the incompat feature is already set. Or fall back to original behavior. But I'm not a fan of using INCOMPAT flags as an indicator of changed fsid/metadata uuid. INCOMPAT feature should not change so easily nor acts as an indicator. That's to say, the flag should only be set at mkfs time, and then never change unlike the 2nd patch (I don't even like btrfstune to change incompat flags). E.g. mkfs.btrfs -O metadata_uuid , then we could use the new way to change fsid without touching metadata uuid. Or we could only use the old method. I disagree, I don't see any benefit in this but only added complexity. Can you elaborate more ? Same here, I see essentially zero benefit to this, and one _big_ drawback, namely that you can't convert an existing volume to use this approach if it's a feature that can only be set at mkfs time. That one drawback means that this is effectively useless for all existing BTRFS volumes, which is a pretty big limitation. I also do think an INCOMPAT feature bit is appropriate here. Volumes with this feature will potentially be enumerated with the wrong UUID on older kernels, which is a pretty big behavioral issue (on the level of completely breaking boot on some systems, keep in mind that almost all major distros use volume UUID's to identify volumes in /etc/fstab). Thanks, Qu So this is something which I'd like to hear from the community. Of course the alternative of rewriting the metadata blocks will be assigne new options - perhaps -m|M ? I've tested this with multiple xfstest runs with the new tools installed as well as running btrfs-progs test and have observed no regressions. Nikolay Borisov (4): btrfs-progs: Add support for metadata_uuid field. btrfstune: Add support for changing the user uuid btrfs-progs: tests: Add tests for changing fsid feature btrfs-progs: Remove fsid/metdata_uuid fields from fs_info btrfstune.c| 174 - check/main.c | 2 +- chunk-recover.c| 17 ++- cmds-filesystem.c |
Re: [PATCH 0/4] Userspace support for FSID change
On 29.08.2018 15:09, Qu Wenruo wrote: > > > On 2018/8/29 下午4:35, Nikolay Borisov wrote: >> Here is the userspace tooling support for utilising the new metadata_uuid >> field, >> enabling the change of fsid without having to rewrite every metadata block. >> This >> patchset consists of adding support for the new field to various tools and >> files (Patch 1). The actual implementation of the new -m|-M options (which >> are >> described in more detail in Patch 2). A new misc-tests testcasei (Patch 3) >> which >> exercises the new options and verifies certain invariants hold (these are >> also >> described in Patch2). Patch 4 is more or less copy of the kernel conuterpart >> just reducing some duplication between btrfs_fs_info and btrfs_fs_devices >> structures. > > So to my understand, now we have another layer of UUID. > > Before we have one fsid, both used in superblock and tree blocks. > > Now we have 2 fsid, the one used in tree blocks are kept the same, but > changed its name to metadata_uuid in superblock. > And superblock::fsid will become a new field, and although they are the > same at mkfs time, they could change several times during its operation. > > This indeed makes uuid change super fast, only needs to update all > superblocks of the fs, instead of all tree blocks. > > However I have one nitpick of the design. Unlike XFS, btrfs supports > multiple devices. > If we have a raid10 fs with 4 devices, and it has already gone through > several UUID change (so its metadata uuid is already different from fsid). > > And during another UUID change procedure, we lost power while only > updated 2 super blocks, what will happen for kernel device assembly? > > (Although considering how fast the UUID change would happen, such case > should be super niche) Then I guess you will be fucked. I'm all ears for suggestion how to rectify this without skyrocketing the complexity. The current UUID rewrite method sets a flag int he superblock that FSID change is in progress and clears it once every metadatablock has been rewritten. I can piggyback on this mechanism but I'm not sure it provides 100% guarantee. Because by the some token you can set this flag, start writing the super blocks then lose power and then only some of the superblocks could have this flag set so we back at square 1. > >> >> The intended usecase of this feature is to give the sysadmin the ability to >> create copies of filesystesm, change their uuid quickly and mount them >> alongside >> the original filesystem for, say, forensic purposes. >> >> One thing which still hasn't been set in stone is whether the new options >> will remain as -m|-M or whether they should subsume the current -u|-U - from >> the point of view of users nothing should change. > > Well, user would be surprised by how fast the new -m is, thus there is > still something changed :) > > I prefer to subsume current -u/-U, and use the new one if the incompat > feature is already set. Or fall back to original behavior. > > But I'm not a fan of using INCOMPAT flags as an indicator of changed > fsid/metadata uuid. > INCOMPAT feature should not change so easily nor acts as an indicator. > > That's to say, the flag should only be set at mkfs time, and then never > change unlike the 2nd patch (I don't even like btrfstune to change > incompat flags). > > E.g. > mkfs.btrfs -O metadata_uuid , then we could use the new way to > change fsid without touching metadata uuid. > Or we could only use the old method. I disagree, I don't see any benefit in this but only added complexity. Can you elaborate more ? > > Thanks, > Qu > >> So this is something which >> I'd like to hear from the community. Of course the alternative of rewriting >> the metadata blocks will be assigne new options - perhaps -m|M ? >> >> I've tested this with multiple xfstest runs with the new tools installed as >> well as running btrfs-progs test and have observed no regressions. >> >> Nikolay Borisov (4): >> btrfs-progs: Add support for metadata_uuid field. >> btrfstune: Add support for changing the user uuid >> btrfs-progs: tests: Add tests for changing fsid feature >> btrfs-progs: Remove fsid/metdata_uuid fields from fs_info >> >> btrfstune.c| 174 >> - >> check/main.c | 2 +- >> chunk-recover.c| 17 ++- >> cmds-filesystem.c | 2 + >> cmds-inspect-dump-super.c | 22 +++- >> convert/common.c | 2 + >> ctree.c| 15 +-- >> ctree.h| 8 +- >> disk-io.c | 62 -- >> image/main.c | 25 +++-- >> tests/misc-tests/033-metadata-uuid/test.sh | 137 +++ >> volumes.c | 37 -- >> volumes.h
Re: [PATCH 0/4] Userspace support for FSID change
On 2018/8/29 下午4:35, Nikolay Borisov wrote: > Here is the userspace tooling support for utilising the new metadata_uuid > field, > enabling the change of fsid without having to rewrite every metadata block. > This > patchset consists of adding support for the new field to various tools and > files (Patch 1). The actual implementation of the new -m|-M options (which > are > described in more detail in Patch 2). A new misc-tests testcasei (Patch 3) > which > exercises the new options and verifies certain invariants hold (these are also > described in Patch2). Patch 4 is more or less copy of the kernel conuterpart > just reducing some duplication between btrfs_fs_info and btrfs_fs_devices > structures. So to my understand, now we have another layer of UUID. Before we have one fsid, both used in superblock and tree blocks. Now we have 2 fsid, the one used in tree blocks are kept the same, but changed its name to metadata_uuid in superblock. And superblock::fsid will become a new field, and although they are the same at mkfs time, they could change several times during its operation. This indeed makes uuid change super fast, only needs to update all superblocks of the fs, instead of all tree blocks. However I have one nitpick of the design. Unlike XFS, btrfs supports multiple devices. If we have a raid10 fs with 4 devices, and it has already gone through several UUID change (so its metadata uuid is already different from fsid). And during another UUID change procedure, we lost power while only updated 2 super blocks, what will happen for kernel device assembly? (Although considering how fast the UUID change would happen, such case should be super niche) > > The intended usecase of this feature is to give the sysadmin the ability to > create copies of filesystesm, change their uuid quickly and mount them > alongside > the original filesystem for, say, forensic purposes. > > One thing which still hasn't been set in stone is whether the new options > will remain as -m|-M or whether they should subsume the current -u|-U - from > the point of view of users nothing should change. Well, user would be surprised by how fast the new -m is, thus there is still something changed :) I prefer to subsume current -u/-U, and use the new one if the incompat feature is already set. Or fall back to original behavior. But I'm not a fan of using INCOMPAT flags as an indicator of changed fsid/metadata uuid. INCOMPAT feature should not change so easily nor acts as an indicator. That's to say, the flag should only be set at mkfs time, and then never change unlike the 2nd patch (I don't even like btrfstune to change incompat flags). E.g. mkfs.btrfs -O metadata_uuid , then we could use the new way to change fsid without touching metadata uuid. Or we could only use the old method. Thanks, Qu > So this is something which > I'd like to hear from the community. Of course the alternative of rewriting > the metadata blocks will be assigne new options - perhaps -m|M ? > > I've tested this with multiple xfstest runs with the new tools installed as > well as running btrfs-progs test and have observed no regressions. > > Nikolay Borisov (4): > btrfs-progs: Add support for metadata_uuid field. > btrfstune: Add support for changing the user uuid > btrfs-progs: tests: Add tests for changing fsid feature > btrfs-progs: Remove fsid/metdata_uuid fields from fs_info > > btrfstune.c| 174 > - > check/main.c | 2 +- > chunk-recover.c| 17 ++- > cmds-filesystem.c | 2 + > cmds-inspect-dump-super.c | 22 +++- > convert/common.c | 2 + > ctree.c| 15 +-- > ctree.h| 8 +- > disk-io.c | 62 -- > image/main.c | 25 +++-- > tests/misc-tests/033-metadata-uuid/test.sh | 137 +++ > volumes.c | 37 -- > volumes.h | 1 + > 13 files changed, 431 insertions(+), 73 deletions(-) > create mode 100755 tests/misc-tests/033-metadata-uuid/test.sh >
[PATCH 0/4] Userspace support for FSID change
Here is the userspace tooling support for utilising the new metadata_uuid field, enabling the change of fsid without having to rewrite every metadata block. This patchset consists of adding support for the new field to various tools and files (Patch 1). The actual implementation of the new -m|-M options (which are described in more detail in Patch 2). A new misc-tests testcasei (Patch 3) which exercises the new options and verifies certain invariants hold (these are also described in Patch2). Patch 4 is more or less copy of the kernel conuterpart just reducing some duplication between btrfs_fs_info and btrfs_fs_devices structures. The intended usecase of this feature is to give the sysadmin the ability to create copies of filesystesm, change their uuid quickly and mount them alongside the original filesystem for, say, forensic purposes. One thing which still hasn't been set in stone is whether the new options will remain as -m|-M or whether they should subsume the current -u|-U - from the point of view of users nothing should change. So this is something which I'd like to hear from the community. Of course the alternative of rewriting the metadata blocks will be assigne new options - perhaps -m|M ? I've tested this with multiple xfstest runs with the new tools installed as well as running btrfs-progs test and have observed no regressions. Nikolay Borisov (4): btrfs-progs: Add support for metadata_uuid field. btrfstune: Add support for changing the user uuid btrfs-progs: tests: Add tests for changing fsid feature btrfs-progs: Remove fsid/metdata_uuid fields from fs_info btrfstune.c| 174 - check/main.c | 2 +- chunk-recover.c| 17 ++- cmds-filesystem.c | 2 + cmds-inspect-dump-super.c | 22 +++- convert/common.c | 2 + ctree.c| 15 +-- ctree.h| 8 +- disk-io.c | 62 -- image/main.c | 25 +++-- tests/misc-tests/033-metadata-uuid/test.sh | 137 +++ volumes.c | 37 -- volumes.h | 1 + 13 files changed, 431 insertions(+), 73 deletions(-) create mode 100755 tests/misc-tests/033-metadata-uuid/test.sh -- 2.7.4
