dcache: get/release read lock in read_seqbegin_or_lock() & friend

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This patch modifies read_seqbegin_or_lock() and need_seqretry() to use
newly introduced read_seqlock_excl() and read_sequnlock_excl()
primitives so that they won't change the sequence number even if they
fall back to take the lock.  This is OK as no change to the protected
data structure is being made.

It will prevent one fallback to lock taking from cascading into a series
of lock taking reducing performance because of the sequence number
change.  It will also allow other sequence readers to go forward while
an exclusive reader lock is taken.

This patch also updates some of the inaccurate comments in the code.

Signed-off-by: Waiman Long <Waiman.Long@hp.com>
To: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

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This commit is contained in:

Waiman Long 2013-09-12 10:55:35 -04:00 • committed by Linus Torvalds

parent 1370e97bb2

commit 1812997720

1 changed files with 16 additions and 15 deletions

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fs/dcache.c

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