Implement create_snapshot interface for ImageFile #392
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Signed-off-by: Xun Chen <xunchen@hust.edu.cn>
BigVan
reviewed
Jan 28, 2026
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| auto upper = new_cfg.upper(); | ||
| auto lowers = new_cfg.lowers(); | ||
| if(lowers[lowers.size()-1].file() != conf.upper().data()) |
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It is unnecessary to keep the same filename, we can seal the upper data file and rename it.
| ssize_t pread(void *buf, size_t count, off_t offset) override | ||
| { | ||
| return m_file->pread(buf, count, offset); | ||
| } |
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I think all I/O requests can be automatically transferred to pread/pwrite via VirtualFile?
| } | ||
| delete m_backing_index; | ||
| if(m_ownership) // !!! | ||
| delete m_backing_index; |
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What this PR does / why we need it:
This PR implements the create_snapshot interface for ImageFile.
The snapshot is created by restacking the current RW layer via m_file->restack(), turning the existing upper layer into a new lower layer and switching to a new upper layer defined in the updated image config.
We also add several helper interfaces in IFileRO and IComboIndex to keep m_lower_file and m_upper_file synchronized. This ensures proper resource cleanup and avoids memory leakage during snapshot creation.
Which issue(s) this PR fixes (optional, in
fixes #<issue number>(, fixes #<issue_number>, ...)format, will close the issue(s) when PR gets merged):Fixes #
Please check the following list: