0b877d09df
Parts of the block layer treat BDS.backing_file as if it were whatever the image header says (i.e., if it is a relative path, it is relative to the overlay), other parts treat it like a cache for bs->backing->bs->filename (relative paths are relative to the CWD). Considering bs->backing->bs->filename exists, let us make it mean the former. Among other things, this now allows the user to specify a base when using qemu-img to commit an image file in a directory that is not the CWD (assuming, everything uses relative filenames). Before this patch: $ ./qemu-img create -f qcow2 foo/bot.qcow2 1M $ ./qemu-img create -f qcow2 -b bot.qcow2 foo/mid.qcow2 $ ./qemu-img create -f qcow2 -b mid.qcow2 foo/top.qcow2 $ ./qemu-img commit -b mid.qcow2 foo/top.qcow2 qemu-img: Did not find 'mid.qcow2' in the backing chain of 'foo/top.qcow2' $ ./qemu-img commit -b foo/mid.qcow2 foo/top.qcow2 qemu-img: Did not find 'foo/mid.qcow2' in the backing chain of 'foo/top.qcow2' $ ./qemu-img commit -b $PWD/foo/mid.qcow2 foo/top.qcow2 qemu-img: Did not find '[...]/foo/mid.qcow2' in the backing chain of 'foo/top.qcow2' After this patch: $ ./qemu-img commit -b mid.qcow2 foo/top.qcow2 Image committed. $ ./qemu-img commit -b foo/mid.qcow2 foo/top.qcow2 qemu-img: Did not find 'foo/mid.qcow2' in the backing chain of 'foo/top.qcow2' $ ./qemu-img commit -b $PWD/foo/mid.qcow2 foo/top.qcow2 Image committed. With this change, bdrv_find_backing_image() must look at whether the user has overridden a BDS's backing file. If so, it can no longer use bs->backing_file, but must instead compare the given filename against the backing node's filename directly. Note that this changes the QAPI output for a node's backing_file. We had very inconsistent output there (sometimes what the image header said, sometimes the actual filename of the backing image). This inconsistent output was effectively useless, so we have to decide one way or the other. Considering that bs->backing_file usually at runtime contained the path to the image relative to qemu's CWD (or absolute), this patch changes QAPI's backing_file to always report the bs->backing->bs->filename from now on. If you want to receive the image header information, you have to refer to full-backing-filename. This necessitates a change to iotest 228. The interesting information it really wanted is the image header, and it can get that now, but it has to use full-backing-filename instead of backing_file. Because of this patch's changes to bs->backing_file's behavior, we also need some reference output changes. Along with the changes to bs->backing_file, stop updating BDS.backing_format in bdrv_backing_attach() as well. This way, ImageInfo's backing-filename and backing-filename-format fields will represent what the image header says and nothing else. iotest 245 changes in behavior: With the backing node no longer overriding the parent node's backing_file string, you can now omit the @backing option when reopening a node with neither a default nor a current backing file even if it used to have a backing node at some point. 273 also changes: The base image is opened without a format layer, so ImageInfo.backing-filename-format used to report "file" for the base image's overlay after blockdev-snapshot. However, the image header never says "file" anywhere, so it now reports $IMGFMT. Signed-off-by: Max Reitz <mreitz@redhat.com>
85 lines
3.8 KiB
Plaintext
85 lines
3.8 KiB
Plaintext
--- Implicit backing file ---
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{"execute": "blockdev-add", "arguments": {"driver": "IMGFMT", "file": {"driver": "file", "filename": "TEST_DIR/PID-top.img"}, "node-name": "node0"}}
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{"return": {}}
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bs->filename: TEST_DIR/PID-top.img
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bs->backing_file: file:TEST_DIR/PID-base.img
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bs->backing->bs->filename: TEST_DIR/PID-base.img
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{"execute": "blockdev-del", "arguments": {"node-name": "node0"}}
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{"return": {}}
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--- change-backing-file ---
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{"execute": "blockdev-add", "arguments": {"driver": "IMGFMT", "file": {"driver": "file", "filename": "TEST_DIR/PID-top.img"}, "node-name": "node0"}}
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{"return": {}}
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{"execute": "change-backing-file", "arguments": {"backing-file": "null-co://", "device": "node0", "image-node-name": "node0"}}
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{"return": {}}
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bs->filename: json:{"backing": {"driver": "IMGFMT", "file": {"driver": "file", "filename": "TEST_DIR/PID-base.img"}}, "driver": "IMGFMT", "file": {"driver": "file", "filename": "TEST_DIR/PID-top.img"}}
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bs->backing_file: null-co://
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bs->backing->bs->filename: TEST_DIR/PID-base.img
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{"execute": "change-backing-file", "arguments": {"backing-file": "TEST_DIR/PID-base.img", "device": "node0", "image-node-name": "node0"}}
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{"return": {}}
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bs->filename: TEST_DIR/PID-top.img
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bs->backing_file: TEST_DIR/PID-base.img
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bs->backing->bs->filename: TEST_DIR/PID-base.img
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{"execute": "change-backing-file", "arguments": {"backing-file": "file:TEST_DIR/PID-base.img", "device": "node0", "image-node-name": "node0"}}
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{"return": {}}
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bs->filename: json:{"backing": {"driver": "IMGFMT", "file": {"driver": "file", "filename": "TEST_DIR/PID-base.img"}}, "driver": "IMGFMT", "file": {"driver": "file", "filename": "TEST_DIR/PID-top.img"}}
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bs->backing_file: file:TEST_DIR/PID-base.img
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bs->backing->bs->filename: TEST_DIR/PID-base.img
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{"execute": "blockdev-del", "arguments": {"node-name": "node0"}}
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{"return": {}}
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{"execute": "blockdev-add", "arguments": {"driver": "IMGFMT", "file": {"driver": "file", "filename": "TEST_DIR/PID-top.img"}, "node-name": "node0"}}
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{"return": {}}
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bs->filename: TEST_DIR/PID-top.img
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bs->backing_file: file:TEST_DIR/PID-base.img
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bs->backing->bs->filename: TEST_DIR/PID-base.img
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{"execute": "blockdev-del", "arguments": {"node-name": "node0"}}
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{"return": {}}
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--- Override backing file ---
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{"execute": "blockdev-add", "arguments": {"driver": "null-co", "node-name": "null"}}
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{"return": {}}
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{"execute": "blockdev-add", "arguments": {"backing": "null", "driver": "IMGFMT", "file": {"driver": "file", "filename": "TEST_DIR/PID-top.img"}, "node-name": "node0"}}
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{"return": {}}
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bs->filename: json:{"backing": {"driver": "null-co"}, "driver": "IMGFMT", "file": {"driver": "file", "filename": "TEST_DIR/PID-top.img"}}
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bs->backing_file: TEST_DIR/PID-base.img
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bs->backing->bs->filename: null-co://
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{"execute": "blockdev-del", "arguments": {"node-name": "node0"}}
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{"return": {}}
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{"execute": "blockdev-del", "arguments": {"node-name": "null"}}
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{"return": {}}
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{"execute": "blockdev-add", "arguments": {"backing": null, "driver": "IMGFMT", "file": {"driver": "file", "filename": "TEST_DIR/PID-top.img"}, "node-name": "node0"}}
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{"return": {}}
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bs->filename: json:{"backing": null, "driver": "IMGFMT", "file": {"driver": "file", "filename": "TEST_DIR/PID-top.img"}}
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bs->backing_file: TEST_DIR/PID-base.img
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bs->backing: (none)
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{"execute": "blockdev-add", "arguments": {"driver": "IMGFMT", "file": {"driver": "file", "filename": "TEST_DIR/PID-base.img"}, "node-name": "original-backing"}}
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{"return": {}}
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{"execute": "blockdev-snapshot", "arguments": {"node": "original-backing", "overlay": "node0"}}
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{"return": {}}
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bs->filename: TEST_DIR/PID-top.img
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bs->backing_file: TEST_DIR/PID-base.img
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bs->backing->bs->filename: TEST_DIR/PID-base.img
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{"execute": "blockdev-del", "arguments": {"node-name": "node0"}}
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{"return": {}}
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{"execute": "blockdev-del", "arguments": {"node-name": "original-backing"}}
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{"return": {}}
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