btrfs-progs: mkfs/rootdir: add hard link support #873
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Can you please rebase the branch? The diff is mixed with all the v6.10.1 changes, I can't do the review properly. |
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Never mind, it was caused by my push of old devel, before the 6.10.1 merge. |
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The new hard link detection and creation support is done by maintaining
an rb tree with the following members:
- st_ino, st_dev
This is to record the stat() report from the host fs.
With this two, we can detect if it's really a hard link (st_dev
determines one filesystem/subvolume, and st_ino determines the inode
number inside the fs).
- root
This is btrfs root pointer. This a special requirement for the recent
introduced "--subvol" option.
As we can have the following corner case:
rootdir/
|- foobar_hardlink1
|- foobar_hardlink2
|- subv/ <- To be a subvolume inside btrfs
|- foobar_hardlink3
In above case, on the host fs, `subv/` directory is just a regular
directory, but in the new btrfs it will be a subvolume.
In that case, `foobar_hardlink3` cannot be created as a hard link,
but a new inode.
- st_nlink and found_nlink
Records the original reported number of links, and the nlinks we
created inside btrfs.
This is recorded in case we created all hard links and can remove
the entry early.
- btrfs_ino
This is the inode number inside btrfs.
And since we can handle hard links safely, remove all the related
warnings, and add a new note for `--subvol` option, warning about the
case where we need to split hard links due to subvolume boundary.
Signed-off-by: Qu Wenruo <[email protected]>
This introduces two new cases: - 3 hardlinks without any subvolume This should results 3 hard links inside the btrfs. - 3 hardlinks, but a subvolume will split 2 of them Then the 2 inside the same subvolume should still report 2 nlinks, but the lone one inside the new subvolume can only report 1 nlink. Signed-off-by: Qu Wenruo <[email protected]>
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kdave
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The new hard link detection and creation support is done by maintaining
an rb tree with the following members:
- st_ino, st_dev
This is to record the stat() report from the host fs.
With this two, we can detect if it's really a hard link (st_dev
determines one filesystem/subvolume, and st_ino determines the inode
number inside the fs).
- root
This is btrfs root pointer. This a special requirement for the recent
introduced "--subvol" option.
As we can have the following corner case:
rootdir/
|- foobar_hardlink1
|- foobar_hardlink2
|- subv/ <- To be a subvolume inside btrfs
|- foobar_hardlink3
In above case, on the host fs, `subv/` directory is just a regular
directory, but in the new btrfs it will be a subvolume.
In that case, `foobar_hardlink3` cannot be created as a hard link,
but a new inode.
- st_nlink and found_nlink
Records the original reported number of links, and the nlinks we
created inside btrfs.
This is recorded in case we created all hard links and can remove
the entry early.
- btrfs_ino
This is the inode number inside btrfs.
And since we can handle hard links safely, remove all the related
warnings, and add a new note for `--subvol` option, warning about the
case where we need to split hard links due to subvolume boundary.
Pull-request: #873
Signed-off-by: Qu Wenruo <[email protected]>
kdave
pushed a commit
that referenced
this pull request
Sep 17, 2024
The new hard link detection and creation support is done by maintaining
an rb tree with the following members:
- st_ino, st_dev
This is to record the stat() report from the host fs.
With this two, we can detect if it's really a hard link (st_dev
determines one filesystem/subvolume, and st_ino determines the inode
number inside the fs).
- root
This is btrfs root pointer. This a special requirement for the recent
introduced "--subvol" option.
As we can have the following corner case:
rootdir/
|- foobar_hardlink1
|- foobar_hardlink2
|- subv/ <- To be a subvolume inside btrfs
|- foobar_hardlink3
In above case, on the host fs, `subv/` directory is just a regular
directory, but in the new btrfs it will be a subvolume.
In that case, `foobar_hardlink3` cannot be created as a hard link,
but a new inode.
- st_nlink and found_nlink
Records the original reported number of links, and the nlinks we
created inside btrfs.
This is recorded in case we created all hard links and can remove
the entry early.
- btrfs_ino
This is the inode number inside btrfs.
And since we can handle hard links safely, remove all the related
warnings, and add a new note for `--subvol` option, warning about the
case where we need to split hard links due to subvolume boundary.
Pull-request: #873
Signed-off-by: Qu Wenruo <[email protected]>
kdave
pushed a commit
that referenced
this pull request
Nov 8, 2024
The new hard link detection and creation support is done by maintaining
an rb tree with the following members:
- st_ino, st_dev
This is to record the stat() report from the host fs.
With this two, we can detect if it's really a hard link (st_dev
determines one filesystem/subvolume, and st_ino determines the inode
number inside the fs).
- root
This is btrfs root pointer. This a special requirement for the recent
introduced "--subvol" option.
As we can have the following corner case:
rootdir/
|- foobar_hardlink1
|- foobar_hardlink2
|- subv/ <- To be a subvolume inside btrfs
|- foobar_hardlink3
In above case, on the host fs, `subv/` directory is just a regular
directory, but in the new btrfs it will be a subvolume.
In that case, `foobar_hardlink3` cannot be created as a hard link,
but a new inode.
- st_nlink and found_nlink
Records the original reported number of links, and the nlinks we
created inside btrfs.
This is recorded in case we created all hard links and can remove
the entry early.
- btrfs_ino
This is the inode number inside btrfs.
And since we can handle hard links safely, remove all the related
warnings, and add a new note for `--subvol` option, warning about the
case where we need to split hard links due to subvolume boundary.
Pull-request: #873
Signed-off-by: Qu Wenruo <[email protected]>
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With the recently reworked --rootdir support, although it solves several
hard link related problems, it splits the hard links into new inodes.
And on each split, it shows a warning on each file with hardlinks.
Although the split behavior doesn't cause any data corruption, it can
still be pretty noisy for rootfs creation, as there are a lot of distros
storing timezone files as hardlinks.
This patchset adds back the hard link detection and creation, with
enhanced handling to co-operate with --subvol option.
The details can be found in the first patch, with the new corner case
introduced by --subvol option.
The second patch enhances the existing --rootdir and --subvol test case
with extra corner cases like hard links, and hard links split by
subvolume boundary.