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a7ecd30c83
We have a unique lock used for controlling adding to the pagecache: the lock has two states, where both states are shared - the lock may be held multiple times for either state - but not both states at the same time. This is exactly what we need for nocow mode locking, so this patch pulls it out of fs.c into its own file. Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
33 lines
693 B
C
33 lines
693 B
C
// SPDX-License-Identifier: GPL-2.0
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#include "two_state_shared_lock.h"
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void bch2_two_state_unlock(two_state_lock_t *lock, int s)
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{
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long i = s ? 1 : -1;
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BUG_ON(atomic_long_read(&lock->v) == 0);
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if (atomic_long_sub_return_release(i, &lock->v) == 0)
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wake_up_all(&lock->wait);
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}
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bool bch2_two_state_trylock(two_state_lock_t *lock, int s)
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{
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long i = s ? 1 : -1;
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long v = atomic_long_read(&lock->v), old;
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do {
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old = v;
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if (i > 0 ? v < 0 : v > 0)
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return false;
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} while ((v = atomic_long_cmpxchg_acquire(&lock->v,
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old, old + i)) != old);
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return true;
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}
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void bch2_two_state_lock(two_state_lock_t *lock, int s)
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{
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wait_event(lock->wait, bch2_two_state_trylock(lock, s));
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}
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