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278f6679f4
The reiserfs write lock replaced the BKL and uses similar semantics. Frederic's locking code makes a distinction between when the lock is nested and when it's being acquired/released, but I don't think that's the right distinction to make. The right distinction is between the lock being released at end-of-use and the lock being released for a schedule. The unlock should return the depth and the lock should restore it, rather than the other way around as it is now. This patch implements that and adds a number of places where the lock should be dropped. Signed-off-by: Jeff Mahoney <jeffm@suse.com>
101 lines
2.6 KiB
C
101 lines
2.6 KiB
C
#include "reiserfs.h"
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#include <linux/mutex.h>
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/*
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* The previous reiserfs locking scheme was heavily based on
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* the tricky properties of the Bkl:
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*
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* - it was acquired recursively by a same task
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* - the performances relied on the release-while-schedule() property
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*
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* Now that we replace it by a mutex, we still want to keep the same
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* recursive property to avoid big changes in the code structure.
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* We use our own lock_owner here because the owner field on a mutex
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* is only available in SMP or mutex debugging, also we only need this field
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* for this mutex, no need for a system wide mutex facility.
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*
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* Also this lock is often released before a call that could block because
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* reiserfs performances were partially based on the release while schedule()
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* property of the Bkl.
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*/
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void reiserfs_write_lock(struct super_block *s)
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{
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struct reiserfs_sb_info *sb_i = REISERFS_SB(s);
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if (sb_i->lock_owner != current) {
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mutex_lock(&sb_i->lock);
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sb_i->lock_owner = current;
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}
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/* No need to protect it, only the current task touches it */
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sb_i->lock_depth++;
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}
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void reiserfs_write_unlock(struct super_block *s)
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{
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struct reiserfs_sb_info *sb_i = REISERFS_SB(s);
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/*
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* Are we unlocking without even holding the lock?
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* Such a situation must raise a BUG() if we don't want
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* to corrupt the data.
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*/
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BUG_ON(sb_i->lock_owner != current);
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if (--sb_i->lock_depth == -1) {
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sb_i->lock_owner = NULL;
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mutex_unlock(&sb_i->lock);
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}
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}
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int __must_check reiserfs_write_unlock_nested(struct super_block *s)
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{
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struct reiserfs_sb_info *sb_i = REISERFS_SB(s);
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int depth;
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/* this can happen when the lock isn't always held */
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if (sb_i->lock_owner != current)
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return -1;
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depth = sb_i->lock_depth;
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sb_i->lock_depth = -1;
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sb_i->lock_owner = NULL;
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mutex_unlock(&sb_i->lock);
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return depth;
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}
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void reiserfs_write_lock_nested(struct super_block *s, int depth)
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{
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struct reiserfs_sb_info *sb_i = REISERFS_SB(s);
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/* this can happen when the lock isn't always held */
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if (depth == -1)
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return;
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mutex_lock(&sb_i->lock);
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sb_i->lock_owner = current;
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sb_i->lock_depth = depth;
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}
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/*
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* Utility function to force a BUG if it is called without the superblock
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* write lock held. caller is the string printed just before calling BUG()
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*/
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void reiserfs_check_lock_depth(struct super_block *sb, char *caller)
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{
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struct reiserfs_sb_info *sb_i = REISERFS_SB(sb);
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WARN_ON(sb_i->lock_depth < 0);
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}
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#ifdef CONFIG_REISERFS_CHECK
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void reiserfs_lock_check_recursive(struct super_block *sb)
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{
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struct reiserfs_sb_info *sb_i = REISERFS_SB(sb);
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WARN_ONCE((sb_i->lock_depth > 0), "Unwanted recursive reiserfs lock!\n");
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}
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#endif
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