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Linux 4.20 compat: Fix VERIFY(RW_READ_HELD(&hash->mh_contents))

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The 4.20 kernel changed the meaning of the rw_semaphore.owner bits,
causing an assertion when loading the module under the 4.20 kernel.
This patch fixes the issue.

Reviewed-by: Chunwei Chen <tuxoko@gmail.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tony Hutter <hutter2@llnl.gov>
Closes #8360 
Closes #8389
This commit is contained in:
Tony Hutter 2019-02-15 12:37:20 -08:00 committed by Brian Behlendorf
parent 2d76ab9e42
commit e73ab1b38c
1 changed files with 45 additions and 10 deletions
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55
include/spl/sys/rwlock.h
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@ -148,16 +148,6 @@ spl_rw_lockdep_on_maybe(krwlock_t *rwp) \
#define spl_rw_lockdep_on_maybe(rwp)
#endif /* CONFIG_LOCKDEP */
static inline int
RW_READ_HELD(krwlock_t *rwp)
{
/*
* Linux 4.8 will set owner to 1 when read held instead of leave it
* NULL. So we check whether owner <= 1.
*/
return (spl_rwsem_is_locked(SEM(rwp)) &&
(unsigned long)rw_owner(rwp) <= 1);
}
static inline int
RW_WRITE_HELD(krwlock_t *rwp)
@ -171,6 +161,51 @@ RW_LOCK_HELD(krwlock_t *rwp)
return (spl_rwsem_is_locked(SEM(rwp)));
}
static inline int
RW_READ_HELD(krwlock_t *rwp)
{
if (!RW_LOCK_HELD(rwp))
return (0);
/*
* rw_semaphore cheat sheet:
*
* < 3.16:
* There's no rw_semaphore.owner, so use rwp.owner instead.
* If rwp.owner == NULL then it's a reader
*
* 3.16 - 4.7:
* rw_semaphore.owner added (https://lwn.net/Articles/596656/)
* and CONFIG_RWSEM_SPIN_ON_OWNER introduced.
* If rw_semaphore.owner == NULL then it's a reader
*
* 4.8 - 4.16.16:
* RWSEM_READER_OWNED added as an internal #define.
* (https://lore.kernel.org/patchwork/patch/678590/)
* If rw_semaphore.owner == 1 then it's a reader
*
* 4.16.17 - 4.19:
* RWSEM_OWNER_UNKNOWN introduced as ((struct task_struct *)-1L)
* (https://do-db2.lkml.org/lkml/2018/5/15/985)
* If rw_semaphore.owner == 1 then it's a reader.
*
* 4.20+:
* RWSEM_OWNER_UNKNOWN changed to ((struct task_struct *)-2L)
* (https://lkml.org/lkml/2018/9/6/986)
* If rw_semaphore.owner & 1 then it's a reader, and also the reader's
* task_struct may be embedded in rw_semaphore->owner.
*/
#if defined(CONFIG_RWSEM_SPIN_ON_OWNER) && defined(RWSEM_OWNER_UNKNOWN)
if (RWSEM_OWNER_UNKNOWN == (struct task_struct *)-2L) {
/* 4.20+ kernels with CONFIG_RWSEM_SPIN_ON_OWNER */
return ((unsigned long) SEM(rwp)->owner & 1);
}
#endif
/* < 4.20 kernel or !CONFIG_RWSEM_SPIN_ON_OWNER */
return (rw_owner(rwp) == NULL || (unsigned long) rw_owner(rwp) == 1);
}
/*
* The following functions must be a #define and not static inline.
* This ensures that the native linux semaphore functions (down/up)