btrfs: avoid pointless wake ups of drew lock readers

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When unlocking a write lock on a drew lock, at btrfs_drew_write_unlock(),
it's pointless to wake up tasks waiting to acquire a read lock if we
didn't decrement the 'writers' counter down to 0, since a read lock can
only be acquired when the counter reaches a value of 0. Doing so is
harmless from a functional point of view, but it's not efficient due to
unnecessarily waking up tasks just for them to sleep again on the
waitqueue.

So change this to wake up readers only if we decremented the 'writers'
counter to 0.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

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Filipe Manana 2024-03-18 11:08:30 +00:00 • committed by David Sterba

parent c66f2afc71

commit c79f57eafc

1 changed files with 6 additions and 2 deletions

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fs/btrfs/locking.c

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