fs_bdev_freeze(9)

💅 fs_bdev_freeze(9)

ok so this is a page out of the Kernel API Manual — yes bestie, the kernel has lore too 🫶

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✨ NAME ✨

fs_bdev_freeze — the function that freezes, like, every superblock hanging off one block device 🧊

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🌸 SYNOPSIS 🌸

int fs_bdev_freeze (struct block_device *bdev );

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🎀 ARGUMENTS 🎀

• bdev — a block device. that's it. that's the whole argument. iconic minimalism tbh 💅

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🦋 DESCRIPTION 🦋

So picture this: you've got a block device, and you want every live superblock using it to just… stop. Freeze. Like a screenshot of the filesystem mid-vibe. That's what fs_bdev_freeze does — it freezes each live superblock that's using bdev. ❄️

Now here's the part that's lowkey important: if a superblock owns several block devices, it gets frozen once per device, and it stays frozen until all of them are thawed. Not a single one. All. 😤

And the block layer? bestie, it nests these freezes for you, so the count stays balanced. no leaks, no drift, no chaos. the way that it just works ✨

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💖 RETURN 💖

Returns 0 on the happy path 🎉 — or, on a single-fs device, the error from (that) one superblock.

When several superblocks share bdev, a per-superblock failure gets swallowed 🙈 (yeah, see above), but a sync_blockdev failure is always reported. no swallowing that one, fr fr.

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🔥 SEE ALSO 🔥

all the friends in the Kernel file ./fs/super.c cinematic universe 👑

• super_lock(9)
• alloc_super(9)
• deactivate_locked_super(9)
• deactivate_super(9)
• grab_super(9)
• retire_super(9)
• generic_shutdown_super(9)
• sget_fc(9)
• iterate_supers_type(9)
• reconfigure_super(9)
• emergency_thaw_all(9)
• get_anon_bdev(9)
• sget_dev(9)
• fs_bdev_thaw(9)
• fs_bdev_file_open_by_dev(9)
• fs_bdev_file_open_by_path(9)
• fs_bdev_unregister(9)
• fs_bdev_file_release(9)
• get_tree_bdev_flags(9)
• get_tree_bdev(9)
• vfs_get_tree(9)
• sb_wait_write(9)
• freeze_super(9)
• thaw_super(9)

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mwah 💜 that's the page! this one's from ./fs, dated October 2026 — go freeze something (responsibly) and thaw it after, bestie 🧊➡️🔥