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Add PF_NOFS debugging flag
PF_NOFS is a per-process debug flag which is set in current->flags to detect when a process is performing an unsafe allocation. All tasks with PF_NOFS set must strictly use KM_PUSHPAGE for allocations because if they enter direct reclaim and initiate I/O they may deadlock. When debugging is disabled, any incorrect usage will be detected and a call stack with a warning will be printed to the console. The flags will then be automatically corrected to allow for safe execution. If debugging is enabled this will be treated as a fatal condition. To avoid any risk of conflicting with the existing PF_ flags. The PF_NOFS bit shadows the rarely used PF_MUTEX_TESTER bit. Only when CONFIG_RT_MUTEX_TESTER is not set, and we know this bit is unused, will the PF_NOFS bit be valid. Happily, most existing distributions ship a kernel with CONFIG_RT_MUTEX_TESTER disabled. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
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@ -55,6 +55,47 @@
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# define __GFP_ZERO 0x8000
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#endif
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/*
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* PF_NOFS is a per-process debug flag which is set in current->flags to
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* detect when a process is performing an unsafe allocation. All tasks
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* with PF_NOFS set must strictly use KM_PUSHPAGE for allocations because
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* if they enter direct reclaim and initiate I/O the may deadlock.
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*
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* When debugging is disabled, any incorrect usage will be detected and
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* a call stack with warning will be printed to the console. The flags
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* will then be automatically corrected to allow for safe execution. If
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* debugging is enabled this will be treated as a fatal condition.
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*
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* To avoid any risk of conflicting with the existing PF_ flags. The
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* PF_NOFS bit shadows the rarely used PF_MUTEX_TESTER bit. Only when
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* CONFIG_RT_MUTEX_TESTER is not set, and we know this bit is unused,
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* will the PF_NOFS bit be valid. Happily, most existing distributions
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* ship a kernel with CONFIG_RT_MUTEX_TESTER disabled.
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*/
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#if !defined(CONFIG_RT_MUTEX_TESTER) && defined(PF_MUTEX_TESTER)
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# define PF_NOFS PF_MUTEX_TESTER
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static inline void
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sanitize_flags(struct task_struct *p, gfp_t *flags)
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{
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if (unlikely((p->flags & PF_NOFS) && (*flags & (__GFP_IO|__GFP_FS)))) {
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# ifdef NDEBUG
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SDEBUG_LIMIT(SD_CONSOLE | SD_WARNING, "Fixing allocation for "
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"task %s (%d) which used GFP flags 0x%x with PF_NOFS set\n",
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p->comm, p->pid, flags);
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spl_debug_dumpstack(p);
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*flags &= ~(__GFP_IO|__GFP_FS);
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# else
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PANIC("FATAL allocation for task %s (%d) which used GFP "
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"flags 0x%x with PF_NOFS set\n", p->comm, p->pid, flags);
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# endif /* NDEBUG */
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}
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}
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#else
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# define PF_NOFS 0x00000000
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# define sanitize_flags(p, fl) ((void)0)
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#endif /* !defined(CONFIG_RT_MUTEX_TESTER) && defined(PF_MUTEX_TESTER) */
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/*
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* __GFP_NOFAIL looks like it will be removed from the kernel perhaps as
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* early as 2.6.32. To avoid this issue when it occurs in upstream kernels
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@ -67,6 +108,8 @@ kmalloc_nofail(size_t size, gfp_t flags)
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{
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void *ptr;
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sanitize_flags(current, &flags);
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do {
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ptr = kmalloc(size, flags);
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} while (ptr == NULL && (flags & __GFP_WAIT));
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@ -79,6 +122,8 @@ kzalloc_nofail(size_t size, gfp_t flags)
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{
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void *ptr;
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sanitize_flags(current, &flags);
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do {
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ptr = kzalloc(size, flags);
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} while (ptr == NULL && (flags & __GFP_WAIT));
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@ -92,6 +137,8 @@ kmalloc_node_nofail(size_t size, gfp_t flags, int node)
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#ifdef HAVE_KMALLOC_NODE
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void *ptr;
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sanitize_flags(current, &flags);
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do {
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ptr = kmalloc_node(size, flags, node);
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} while (ptr == NULL && (flags & __GFP_WAIT));
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@ -107,6 +154,8 @@ vmalloc_nofail(size_t size, gfp_t flags)
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{
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void *ptr;
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sanitize_flags(current, &flags);
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/*
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* Retry failed __vmalloc() allocations once every second. The
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* rational for the delay is that the likely failure modes are:
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