forked from luck/tmp_suning_uos_patched
c4a62ca362
When we relax the reiserfs lock to avoid creating unwanted dependencies against others locks while grabbing these, we want to ensure it has not been taken recursively, otherwise the lock won't be really relaxed. Only its depth will be decreased. The unwanted dependency would then actually happen. To prevent from that, add a reiserfs_lock_check_recursive() call in the places that need it. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Alexander Beregalov <a.beregalov@gmail.com> Cc: Chris Mason <chris.mason@oracle.com> Cc: Ingo Molnar <mingo@elte.hu>
98 lines
2.6 KiB
C
98 lines
2.6 KiB
C
#include <linux/reiserfs_fs.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 partialy 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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/*
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* If we already own the lock, just exit and don't increase the depth.
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* Useful when we don't want to lock more than once.
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*
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* We always return the lock_depth we had before calling
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* this function.
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*/
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int reiserfs_write_lock_once(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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return sb_i->lock_depth++;
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}
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return sb_i->lock_depth;
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}
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void reiserfs_write_unlock_once(struct super_block *s, int lock_depth)
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{
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if (lock_depth == -1)
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reiserfs_write_unlock(s);
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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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if (sb_i->lock_depth < 0)
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reiserfs_panic(sb, "%s called without kernel lock held %d",
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caller);
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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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