grab_super(9)

💅 grab_super(9) — the kernel API manual, but make it make sense 🎀

okay so bestie, we're in section 9 of the kernel API manual today (yes, the kernel kernel), and the star of the show is grab_super. it's a little function living over in ./fs/super.c and honestly it's giving "bouncer at the club of mounted filesystems" energy. let's get into it 💖

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✨ NAME ✨

grab_super — acquire an active reference to a superblock. that's it, that's the whole vibe. it grabs. it supers. 🔥

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🌸 SYNOPSIS 🌸

bool grab_super (struct super_block *sb );

look at her. one argument, returns a bool, no notes. iconic. 💅

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🦋 ARGUMENTS 🦋

• sb — the superblock you wanna acquire, bestie. that's the target. 🎯

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👑 DESCRIPTION 👑

so here's the tea ☕ — grab_super acquires a temporary reference on a superblock, and then it tries to trade that temp reference for an active reference. like, it's holding a lil placeholder spot in line and hoping the bouncer lets it in for real. no cap.

where does this come up? in sget_fc, that's where. grab_super is used there to wait for a superblock to do one of two things:

1. become SB_BORN (glow up complete ✨), or
2. pass through sb->kill and get marked as SB_DEAD (rip bozo 💀)

either way, it's waiting for the superblock to pick a lane. main character energy fr fr. 🧚

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⭐ RETURN ⭐

• returns true if an active reference could be acquired 🎉
• returns false if not 🙈

that's it. binary queen. bool supremacy. 💜

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🌈 SEE ALSO 🌈

the whole friend group, gathered here in ./fs (kernel file ./fs/super.c, to be specific):

• super_lock(9)
• alloc_super(9)
• deactivate_locked_super(9)
• deactivate_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_freeze(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)

go read all of them, i'll wait. 🫶

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lowkey a reminder that this whole page lives under ./fs in the kernel tree — that's the directory, bestie, not a suggestion.

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and that's the page! 💖 this lil writeup came from ./fs, dated October 2026, and it's the grab_super(9) entry — go off, kernel docs, you ate. 🍓✨