Mount volumes with the runtime's discard and the record's own options by MayCXC · Pull Request #2175 · apple/container

MayCXC · 2026-08-27T20:23:59Z

Type of Change

Bug fix
New feature
Breaking change
Documentation update

Motivation and Context

A volume's ext4 sits on a sparse host file the service created, so the blocks a workload frees belong back on the host as it runs. That is the runtime's concern, owned where the mount is assembled beside the caching and sync modes the runtime already sets there: ext4 volumes mount with continuous discard on every attachment, and a read-only mount parses the option as a no-op.

volume create --opt also stored driver options the mount path never read back. The local driver's spelling for a volume's own mount options is the o key, a comma separated list the way docker's local driver takes it, and docker never injects defaults into it: everything in o is what the caller named. o resolves into each attachment's options now, split the way the attachment's own option suffix already is, so what a volume was created with rides along everywhere it attaches, and the user's list stays exactly the user's.

Adjacent: #2021 reports the analogous non-release of freed space for virtio-fs bind mounts, which this does not address; #1940 asks for the supported --volume options to be documented.

Testing

Tested locally
Added/updated tests
Added/updated docs

New integration coverage reads /proc/mounts inside the container: an ext4 volume's line holds discard on a plain-created volume, and a volume created with --opt o=noatime mounts with its record's option beside the runtime's discard.

Integration suite: 397 passed. Unit suite: 772 passed. make fmt, make check clean.

A volume's ext4 sits on a sparse host file the service created, so the blocks a workload frees belong back on the host as it runs. That is the runtime's concern, owned where the mount is assembled beside the caching and sync modes the runtime already sets there: ext4 volumes mount with continuous discard on every attachment, and a read only mount parses the option as a no-op. volume create --opt also stored driver options the mount path never read back. The local driver's spelling for a volume's own mount options is the o key, a comma separated list the way docker's local driver takes it, and docker never injects defaults into it: everything in o is what the caller named. Resolve o into each attachment's options, split the way the attachment's own option suffix already is, so what a volume was created with rides along everywhere it attaches, and the user's list stays exactly the user's.

/proc/mounts carries the truth: an ext4 volume's line holds discard on a plain-created volume, and a volume created with --opt o=noatime mounts with its record's option beside the runtime's discard.

MayCXC · 2026-08-27T20:23:59Z

Type of Change

Bug fix
New feature
Breaking change
Documentation update

Motivation and Context

Closes#2168.

A volume's ext4 sits on a sparse host file the service created, so the blocks a workload frees belong back on the host as it runs. That is the runtime's concern, owned where the mount is assembled beside the caching and sync modes the runtime already sets there: ext4 volumes mount with continuous discard on every attachment, and a read-only mount parses the option as a no-op.

volume create --opt also stored driver options the mount path never read back. The local driver's spelling for a volume's own mount options is the o key, a comma separated list the way docker's local driver takes it, and docker never injects defaults into it: everything in o is what the caller named. o resolves into each attachment's options now, split the way the attachment's own option suffix already is, so what a volume was created with rides along everywhere it attaches, and the user's list stays exactly the user's.

Adjacent: #2021 reports the analogous non-release of freed space for virtio-fs bind mounts, which this does not address; #1940 asks for the supported --volume options to be documented.

Testing

Tested locally
Added/updated tests
Added/updated docs

New integration coverage reads /proc/mounts inside the container: an ext4 volume's line holds discard on a plain-created volume, and a volume created with --opt o=noatime mounts with its record's option beside the runtime's discard.

Integration suite: 397 passed. Unit suite: 772 passed. make fmt, make check clean.

A volume's ext4 sits on a sparse host file the service created, so the blocks a workload frees belong back on the host as it runs. That is the runtime's concern, owned where the mount is assembled beside the caching and sync modes the runtime already sets there: ext4 volumes mount with continuous discard on every attachment, and a read only mount parses the option as a no-op. volume create --opt also stored driver options the mount path never read back. The local driver's spelling for a volume's own mount options is the o key, a comma separated list the way docker's local driver takes it, and docker never injects defaults into it: everything in o is what the caller named. Resolve o into each attachment's options, split the way the attachment's own option suffix already is, so what a volume was created with rides along everywhere it attaches, and the user's list stays exactly the user's.

/proc/mounts carries the truth: an ext4 volume's line holds discard on a plain-created volume, and a volume created with --opt o=noatime mounts with its record's option beside the runtime's discard.

MayCXC · 2026-08-27T20:23:59Z

Type of Change

Bug fix
New feature
Breaking change
Documentation update

Motivation and Context

Closes#2168.

A volume's ext4 sits on a sparse host file the service created, so the blocks a workload frees belong back on the host as it runs. That is the runtime's concern, owned where the mount is assembled beside the caching and sync modes the runtime already sets there: ext4 volumes mount with continuous discard on every attachment, and a read-only mount parses the option as a no-op.

volume create --opt also stored driver options the mount path never read back. The local driver's spelling for a volume's own mount options is the o key, a comma separated list the way docker's local driver takes it, and docker never injects defaults into it: everything in o is what the caller named. o resolves into each attachment's options now, split the way the attachment's own option suffix already is, so what a volume was created with rides along everywhere it attaches, and the user's list stays exactly the user's.

Adjacent: #2021 reports the analogous non-release of freed space for virtio-fs bind mounts, which this does not address; #1940 asks for the supported --volume options to be documented.

Testing

Tested locally
Added/updated tests
Added/updated docs

New integration coverage reads /proc/mounts inside the container: an ext4 volume's line holds discard on a plain-created volume, and a volume created with --opt o=noatime mounts with its record's option beside the runtime's discard.

Integration suite: 397 passed. Unit suite: 772 passed. make fmt, make check clean.

A volume's ext4 sits on a sparse host file the service created, so the blocks a workload frees belong back on the host as it runs. That is the runtime's concern, owned where the mount is assembled beside the caching and sync modes the runtime already sets there: ext4 volumes mount with continuous discard on every attachment, and a read only mount parses the option as a no-op. volume create --opt also stored driver options the mount path never read back. The local driver's spelling for a volume's own mount options is the o key, a comma separated list the way docker's local driver takes it, and docker never injects defaults into it: everything in o is what the caller named. Resolve o into each attachment's options, split the way the attachment's own option suffix already is, so what a volume was created with rides along everywhere it attaches, and the user's list stays exactly the user's.

/proc/mounts carries the truth: an ext4 volume's line holds discard on a plain-created volume, and a volume created with --opt o=noatime mounts with its record's option beside the runtime's discard.

MayCXC · 2026-08-27T20:23:59Z

Type of Change

Bug fix
New feature
Breaking change
Documentation update

Motivation and Context

Closes#2168.

A volume's ext4 sits on a sparse host file the service created, so the blocks a workload frees belong back on the host as it runs. That is the runtime's concern, owned where the mount is assembled beside the caching and sync modes the runtime already sets there: ext4 volumes mount with continuous discard on every attachment, and a read-only mount parses the option as a no-op.

volume create --opt also stored driver options the mount path never read back. The local driver's spelling for a volume's own mount options is the o key, a comma separated list the way docker's local driver takes it, and docker never injects defaults into it: everything in o is what the caller named. o resolves into each attachment's options now, split the way the attachment's own option suffix already is, so what a volume was created with rides along everywhere it attaches, and the user's list stays exactly the user's.

Adjacent: #2021 reports the analogous non-release of freed space for virtio-fs bind mounts, which this does not address; #1940 asks for the supported --volume options to be documented.

Testing

Tested locally
Added/updated tests
Added/updated docs

New integration coverage reads /proc/mounts inside the container: an ext4 volume's line holds discard on a plain-created volume, and a volume created with --opt o=noatime mounts with its record's option beside the runtime's discard.

Integration suite: 397 passed. Unit suite: 772 passed. make fmt, make check clean.

A volume's ext4 sits on a sparse host file the service created, so the blocks a workload frees belong back on the host as it runs. That is the runtime's concern, owned where the mount is assembled beside the caching and sync modes the runtime already sets there: ext4 volumes mount with continuous discard on every attachment, and a read only mount parses the option as a no-op. volume create --opt also stored driver options the mount path never read back. The local driver's spelling for a volume's own mount options is the o key, a comma separated list the way docker's local driver takes it, and docker never injects defaults into it: everything in o is what the caller named. Resolve o into each attachment's options, split the way the attachment's own option suffix already is, so what a volume was created with rides along everywhere it attaches, and the user's list stays exactly the user's.

/proc/mounts carries the truth: an ext4 volume's line holds discard on a plain-created volume, and a volume created with --opt o=noatime mounts with its record's option beside the runtime's discard.

MayCXC · 2026-08-27T20:23:59Z

Type of Change

Bug fix
New feature
Breaking change
Documentation update

Motivation and Context

Closes#2168.

A volume's ext4 sits on a sparse host file the service created, so the blocks a workload frees belong back on the host as it runs. That is the runtime's concern, owned where the mount is assembled beside the caching and sync modes the runtime already sets there: ext4 volumes mount with continuous discard on every attachment, and a read-only mount parses the option as a no-op.

volume create --opt also stored driver options the mount path never read back. The local driver's spelling for a volume's own mount options is the o key, a comma separated list the way docker's local driver takes it, and docker never injects defaults into it: everything in o is what the caller named. o resolves into each attachment's options now, split the way the attachment's own option suffix already is, so what a volume was created with rides along everywhere it attaches, and the user's list stays exactly the user's.

Adjacent: #2021 reports the analogous non-release of freed space for virtio-fs bind mounts, which this does not address; #1940 asks for the supported --volume options to be documented.

Testing

Tested locally
Added/updated tests
Added/updated docs

New integration coverage reads /proc/mounts inside the container: an ext4 volume's line holds discard on a plain-created volume, and a volume created with --opt o=noatime mounts with its record's option beside the runtime's discard.

Integration suite: 397 passed. Unit suite: 772 passed. make fmt, make check clean.

A volume's ext4 sits on a sparse host file the service created, so the blocks a workload frees belong back on the host as it runs. That is the runtime's concern, owned where the mount is assembled beside the caching and sync modes the runtime already sets there: ext4 volumes mount with continuous discard on every attachment, and a read only mount parses the option as a no-op. volume create --opt also stored driver options the mount path never read back. The local driver's spelling for a volume's own mount options is the o key, a comma separated list the way docker's local driver takes it, and docker never injects defaults into it: everything in o is what the caller named. Resolve o into each attachment's options, split the way the attachment's own option suffix already is, so what a volume was created with rides along everywhere it attaches, and the user's list stays exactly the user's.

/proc/mounts carries the truth: an ext4 volume's line holds discard on a plain-created volume, and a volume created with --opt o=noatime mounts with its record's option beside the runtime's discard.

MayCXC · 2026-08-27T20:23:59Z

Type of Change

Bug fix
New feature
Breaking change
Documentation update

Motivation and Context

Closes#2168.

A volume's ext4 sits on a sparse host file the service created, so the blocks a workload frees belong back on the host as it runs. That is the runtime's concern, owned where the mount is assembled beside the caching and sync modes the runtime already sets there: ext4 volumes mount with continuous discard on every attachment, and a read-only mount parses the option as a no-op.

volume create --opt also stored driver options the mount path never read back. The local driver's spelling for a volume's own mount options is the o key, a comma separated list the way docker's local driver takes it, and docker never injects defaults into it: everything in o is what the caller named. o resolves into each attachment's options now, split the way the attachment's own option suffix already is, so what a volume was created with rides along everywhere it attaches, and the user's list stays exactly the user's.

Adjacent: #2021 reports the analogous non-release of freed space for virtio-fs bind mounts, which this does not address; #1940 asks for the supported --volume options to be documented.

Testing

Tested locally
Added/updated tests
Added/updated docs

New integration coverage reads /proc/mounts inside the container: an ext4 volume's line holds discard on a plain-created volume, and a volume created with --opt o=noatime mounts with its record's option beside the runtime's discard.

Integration suite: 397 passed. Unit suite: 772 passed. make fmt, make check clean.

A volume's ext4 sits on a sparse host file the service created, so the blocks a workload frees belong back on the host as it runs. That is the runtime's concern, owned where the mount is assembled beside the caching and sync modes the runtime already sets there: ext4 volumes mount with continuous discard on every attachment, and a read only mount parses the option as a no-op. volume create --opt also stored driver options the mount path never read back. The local driver's spelling for a volume's own mount options is the o key, a comma separated list the way docker's local driver takes it, and docker never injects defaults into it: everything in o is what the caller named. Resolve o into each attachment's options, split the way the attachment's own option suffix already is, so what a volume was created with rides along everywhere it attaches, and the user's list stays exactly the user's.

/proc/mounts carries the truth: an ext4 volume's line holds discard on a plain-created volume, and a volume created with --opt o=noatime mounts with its record's option beside the runtime's discard.

MayCXC · 2026-08-27T20:23:59Z

Type of Change

Bug fix
New feature
Breaking change
Documentation update

Motivation and Context

Closes#2168.

A volume's ext4 sits on a sparse host file the service created, so the blocks a workload frees belong back on the host as it runs. That is the runtime's concern, owned where the mount is assembled beside the caching and sync modes the runtime already sets there: ext4 volumes mount with continuous discard on every attachment, and a read-only mount parses the option as a no-op.

volume create --opt also stored driver options the mount path never read back. The local driver's spelling for a volume's own mount options is the o key, a comma separated list the way docker's local driver takes it, and docker never injects defaults into it: everything in o is what the caller named. o resolves into each attachment's options now, split the way the attachment's own option suffix already is, so what a volume was created with rides along everywhere it attaches, and the user's list stays exactly the user's.

Adjacent: #2021 reports the analogous non-release of freed space for virtio-fs bind mounts, which this does not address; #1940 asks for the supported --volume options to be documented.

Testing

Tested locally
Added/updated tests
Added/updated docs

New integration coverage reads /proc/mounts inside the container: an ext4 volume's line holds discard on a plain-created volume, and a volume created with --opt o=noatime mounts with its record's option beside the runtime's discard.

Integration suite: 397 passed. Unit suite: 772 passed. make fmt, make check clean.

A volume's ext4 sits on a sparse host file the service created, so the blocks a workload frees belong back on the host as it runs. That is the runtime's concern, owned where the mount is assembled beside the caching and sync modes the runtime already sets there: ext4 volumes mount with continuous discard on every attachment, and a read only mount parses the option as a no-op. volume create --opt also stored driver options the mount path never read back. The local driver's spelling for a volume's own mount options is the o key, a comma separated list the way docker's local driver takes it, and docker never injects defaults into it: everything in o is what the caller named. Resolve o into each attachment's options, split the way the attachment's own option suffix already is, so what a volume was created with rides along everywhere it attaches, and the user's list stays exactly the user's.

/proc/mounts carries the truth: an ext4 volume's line holds discard on a plain-created volume, and a volume created with --opt o=noatime mounts with its record's option beside the runtime's discard.

MayCXC · 2026-08-27T20:23:59Z

Type of Change

Bug fix
New feature
Breaking change
Documentation update

Motivation and Context

Closes#2168.

A volume's ext4 sits on a sparse host file the service created, so the blocks a workload frees belong back on the host as it runs. That is the runtime's concern, owned where the mount is assembled beside the caching and sync modes the runtime already sets there: ext4 volumes mount with continuous discard on every attachment, and a read-only mount parses the option as a no-op.

volume create --opt also stored driver options the mount path never read back. The local driver's spelling for a volume's own mount options is the o key, a comma separated list the way docker's local driver takes it, and docker never injects defaults into it: everything in o is what the caller named. o resolves into each attachment's options now, split the way the attachment's own option suffix already is, so what a volume was created with rides along everywhere it attaches, and the user's list stays exactly the user's.

Adjacent: #2021 reports the analogous non-release of freed space for virtio-fs bind mounts, which this does not address; #1940 asks for the supported --volume options to be documented.

Testing

Tested locally
Added/updated tests
Added/updated docs

New integration coverage reads /proc/mounts inside the container: an ext4 volume's line holds discard on a plain-created volume, and a volume created with --opt o=noatime mounts with its record's option beside the runtime's discard.

Integration suite: 397 passed. Unit suite: 772 passed. make fmt, make check clean.

A volume's ext4 sits on a sparse host file the service created, so the blocks a workload frees belong back on the host as it runs. That is the runtime's concern, owned where the mount is assembled beside the caching and sync modes the runtime already sets there: ext4 volumes mount with continuous discard on every attachment, and a read only mount parses the option as a no-op. volume create --opt also stored driver options the mount path never read back. The local driver's spelling for a volume's own mount options is the o key, a comma separated list the way docker's local driver takes it, and docker never injects defaults into it: everything in o is what the caller named. Resolve o into each attachment's options, split the way the attachment's own option suffix already is, so what a volume was created with rides along everywhere it attaches, and the user's list stays exactly the user's.

/proc/mounts carries the truth: an ext4 volume's line holds discard on a plain-created volume, and a volume created with --opt o=noatime mounts with its record's option beside the runtime's discard.

MayCXC added 2 commits August 27, 2026 20:16