Remove BUG/BUG_ON from androind/ion
-v4: some changes based on Dan Carpenter review: - Remove error check at ion_page_pool_remove (conditions are impossible) - Remove error check at opn_page_pool_alloc - restore WARN_ON at ion_page_pool_free - Remove unnecessary error check at ion_page_pool_shrink - Add /* This is impossible. */ comment at order_to_index - Remove error handling of order_to_index
-v3: remove WARN/WARN_ON as Gerg KH suggests
-v2: add error check to order_to_index callers
Tomer Samara (2): staging: android: Remove BUG_ON from ion_page_pool.c staging: android: Remove BUG from ion_system_heap.c
drivers/staging/android/ion/ion_page_pool.c | 6 +----- drivers/staging/android/ion/ion_system_heap.c | 2 +- 2 files changed, 2 insertions(+), 6 deletions(-)
BUG_ON() is removed at ion_page_pool.c
Fixes the following issue: Avoid crashing the kernel - try using WARN_ON & recovery code ratherthan BUG() or BUG_ON().
Signed-off-by: Tomer Samara tomersamara98@gmail.com --- drivers/staging/android/ion/ion_page_pool.c | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-)
diff --git a/drivers/staging/android/ion/ion_page_pool.c b/drivers/staging/android/ion/ion_page_pool.c index 0198b886d906..a3ed3bfd47ee 100644 --- a/drivers/staging/android/ion/ion_page_pool.c +++ b/drivers/staging/android/ion/ion_page_pool.c @@ -46,11 +46,9 @@ static struct page *ion_page_pool_remove(struct ion_page_pool *pool, bool high) struct page *page;
if (high) { - BUG_ON(!pool->high_count); page = list_first_entry(&pool->high_items, struct page, lru); pool->high_count--; } else { - BUG_ON(!pool->low_count); page = list_first_entry(&pool->low_items, struct page, lru); pool->low_count--; } @@ -65,8 +63,6 @@ struct page *ion_page_pool_alloc(struct ion_page_pool *pool) { struct page *page = NULL;
- BUG_ON(!pool); - mutex_lock(&pool->mutex); if (pool->high_count) page = ion_page_pool_remove(pool, true); @@ -82,7 +78,7 @@ struct page *ion_page_pool_alloc(struct ion_page_pool *pool)
void ion_page_pool_free(struct ion_page_pool *pool, struct page *page) { - BUG_ON(pool->order != compound_order(page)); + WARN_ON(pool->order != compound_order(page))
ion_page_pool_add(pool, page); }
On Fri, Aug 21, 2020 at 06:27:37PM +0300, Tomer Samara wrote:
BUG_ON() is removed at ion_page_pool.c
Fixes the following issue: Avoid crashing the kernel - try using WARN_ON & recovery code ratherthan BUG() or BUG_ON().
Signed-off-by: Tomer Samara tomersamara98@gmail.com
You should put a note here about what changed between v3 vs v4. Like so: --- v4: Just remove the BUG_ON()s instead of adding new returns. v3: Hand the new return paths or whatever.
Anyway, looks good.
Reviewed-by: Dan Carpenter dan.carpenter@oracle.com
regards, dan carpenter
Remove BUG() from ion_sytem_heap.c
this fix the following checkpatch issue: Avoid crashing the kernel - try using WARN_ON & recovery code ratherthan BUG() or BUG_ON().
Signed-off-by: Tomer Samara tomersamara98@gmail.com --- drivers/staging/android/ion/ion_system_heap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/staging/android/ion/ion_system_heap.c b/drivers/staging/android/ion/ion_system_heap.c index eac0632ab4e8..00d6154aec34 100644 --- a/drivers/staging/android/ion/ion_system_heap.c +++ b/drivers/staging/android/ion/ion_system_heap.c @@ -30,7 +30,7 @@ static int order_to_index(unsigned int order) for (i = 0; i < NUM_ORDERS; i++) if (order == orders[i]) return i; - BUG(); + /* This is impossible. */ return -1; }
On 8/21/20 8:28 AM, Tomer Samara wrote:
Remove BUG() from ion_sytem_heap.c
this fix the following checkpatch issue: Avoid crashing the kernel - try using WARN_ON & recovery code ratherthan BUG() or BUG_ON().
Signed-off-by: Tomer Samara tomersamara98@gmail.com
drivers/staging/android/ion/ion_system_heap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/staging/android/ion/ion_system_heap.c b/drivers/staging/android/ion/ion_system_heap.c index eac0632ab4e8..00d6154aec34 100644 --- a/drivers/staging/android/ion/ion_system_heap.c +++ b/drivers/staging/android/ion/ion_system_heap.c @@ -30,7 +30,7 @@ static int order_to_index(unsigned int order) for (i = 0; i < NUM_ORDERS; i++) if (order == orders[i]) return i;
- BUG();
- /* This is impossible. */ return -1;
}
Hi, Please explain why this is impossible.
If some caller calls order_to_index(5), it will return -1, yes?
On Fri, Aug 21, 2020 at 09:25:26AM -0700, Randy Dunlap wrote:
On 8/21/20 8:28 AM, Tomer Samara wrote:
Remove BUG() from ion_sytem_heap.c
this fix the following checkpatch issue: Avoid crashing the kernel - try using WARN_ON & recovery code ratherthan BUG() or BUG_ON().
Signed-off-by: Tomer Samara tomersamara98@gmail.com
drivers/staging/android/ion/ion_system_heap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/staging/android/ion/ion_system_heap.c b/drivers/staging/android/ion/ion_system_heap.c index eac0632ab4e8..00d6154aec34 100644 --- a/drivers/staging/android/ion/ion_system_heap.c +++ b/drivers/staging/android/ion/ion_system_heap.c @@ -30,7 +30,7 @@ static int order_to_index(unsigned int order) for (i = 0; i < NUM_ORDERS; i++) if (order == orders[i]) return i;
- BUG();
- /* This is impossible. */ return -1;
}
Hi, Please explain why this is impossible.
If some caller calls order_to_index(5), it will return -1, yes?
-- ~Randy
As Dan Carpenter says here https://lkml.kernel.org/lkml/cover.1597865771.git.tomersamara98@gmail.com/T/.... After looking at callers we see that order_to_index called from 2 functions: - alloc_buffer_page called from alloc_largest_available which loop over all legit order nubmers ( Flow: alloc_largest_available-->alloc_buffer_page-->order_to_index )
- free_buffer_page takes the order using compound_order, which return 0 or the order number for the page, this function has 2 callers too, ion_system_heap_allocate (which called it in case of failure at sg_alloc_table, thus calling from this flow will no casue error) and ion_system_heap_free (which will be called on every sg table in the buffer that allocated good, meaning from this flow also error will not be created). ( Flows: ion_system_heap_free --> free_buffer_page --> order_to_index ion_system_heap_allocate --> free_buffer_page --> order_to_index )
Of course if some user will use this function with wrong order number he will be able to get this -1. So should I remove this comment and resotre the error checks? Btw, this is the same reason that I dropped the error check at ion_page_pool_shrink, so should I restore here also?
Thanks, Tomer Samara
On 8/22/20 2:34 AM, Tomer Samara wrote:
On Fri, Aug 21, 2020 at 09:25:26AM -0700, Randy Dunlap wrote:
On 8/21/20 8:28 AM, Tomer Samara wrote:
Remove BUG() from ion_sytem_heap.c
this fix the following checkpatch issue: Avoid crashing the kernel - try using WARN_ON & recovery code ratherthan BUG() or BUG_ON().
Signed-off-by: Tomer Samara tomersamara98@gmail.com
drivers/staging/android/ion/ion_system_heap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/staging/android/ion/ion_system_heap.c b/drivers/staging/android/ion/ion_system_heap.c index eac0632ab4e8..00d6154aec34 100644 --- a/drivers/staging/android/ion/ion_system_heap.c +++ b/drivers/staging/android/ion/ion_system_heap.c @@ -30,7 +30,7 @@ static int order_to_index(unsigned int order) for (i = 0; i < NUM_ORDERS; i++) if (order == orders[i]) return i;
- BUG();
- /* This is impossible. */ return -1;
}
Hi, Please explain why this is impossible.
If some caller calls order_to_index(5), it will return -1, yes?
-- ~Randy
As Dan Carpenter says here https://lkml.kernel.org/lkml/cover.1597865771.git.tomersamara98@gmail.com/T/.... After looking at callers we see that order_to_index called from 2 functions:
alloc_buffer_page called from alloc_largest_available which loop over all legit order nubmers ( Flow: alloc_largest_available-->alloc_buffer_page-->order_to_index )
free_buffer_page takes the order using compound_order, which return 0 or the order number for the page, this function has 2 callers too, ion_system_heap_allocate (which called it in case of failure at sg_alloc_table, thus calling from this flow will no casue error) and ion_system_heap_free (which will be called on every sg table in the buffer that allocated good, meaning from this flow also error will not be created). ( Flows: ion_system_heap_free --> free_buffer_page --> order_to_index ion_system_heap_allocate --> free_buffer_page --> order_to_index )
Of course if some user will use this function with wrong order number he will be able to get this -1. So should I remove this comment and resotre the error checks?
I think so, but that's just an opinion.
Btw, this is the same reason that I dropped the error check at ion_page_pool_shrink, so should I restore here also?
IMO yes.
Getting rid of BUG()s is a good goal, but usually it's not so easy.
thanks.
On Fri, Aug 21, 2020 at 09:25:26AM -0700, Randy Dunlap wrote:
On 8/21/20 8:28 AM, Tomer Samara wrote:
Remove BUG() from ion_sytem_heap.c
this fix the following checkpatch issue: Avoid crashing the kernel - try using WARN_ON & recovery code ratherthan BUG() or BUG_ON().
Signed-off-by: Tomer Samara tomersamara98@gmail.com
drivers/staging/android/ion/ion_system_heap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/staging/android/ion/ion_system_heap.c b/drivers/staging/android/ion/ion_system_heap.c index eac0632ab4e8..00d6154aec34 100644 --- a/drivers/staging/android/ion/ion_system_heap.c +++ b/drivers/staging/android/ion/ion_system_heap.c @@ -30,7 +30,7 @@ static int order_to_index(unsigned int order) for (i = 0; i < NUM_ORDERS; i++) if (order == orders[i]) return i;
- BUG();
- /* This is impossible. */ return -1;
}
Hi, Please explain why this is impossible.
If some caller calls order_to_index(5), it will return -1, yes?
I was happy enough with the comment as-is given that I suggested it. But an alternative comment could be "/* This is impossible. We always pass valid values to this function. */
regards, dan carpenter
On Mon, Aug 24, 2020 at 02:24:57PM +0300, Dan Carpenter wrote:
On Fri, Aug 21, 2020 at 09:25:26AM -0700, Randy Dunlap wrote:
On 8/21/20 8:28 AM, Tomer Samara wrote:
Remove BUG() from ion_sytem_heap.c
this fix the following checkpatch issue: Avoid crashing the kernel - try using WARN_ON & recovery code ratherthan BUG() or BUG_ON().
Signed-off-by: Tomer Samara tomersamara98@gmail.com
drivers/staging/android/ion/ion_system_heap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/staging/android/ion/ion_system_heap.c b/drivers/staging/android/ion/ion_system_heap.c index eac0632ab4e8..00d6154aec34 100644 --- a/drivers/staging/android/ion/ion_system_heap.c +++ b/drivers/staging/android/ion/ion_system_heap.c @@ -30,7 +30,7 @@ static int order_to_index(unsigned int order) for (i = 0; i < NUM_ORDERS; i++) if (order == orders[i]) return i;
- BUG();
- /* This is impossible. */ return -1;
}
Hi, Please explain why this is impossible.
If some caller calls order_to_index(5), it will return -1, yes?
I was happy enough with the comment as-is given that I suggested it. But an alternative comment could be "/* This is impossible. We always pass valid values to this function. */
Another option is to just change the BUG_ON() to a WARN_ON(). I feel like that communicates the same thing but makes checkpatch happy.
regards, dan carpenter
On Mon, Aug 24, 2020 at 02:27:08PM +0300, Dan Carpenter wrote:
On Mon, Aug 24, 2020 at 02:24:57PM +0300, Dan Carpenter wrote:
On Fri, Aug 21, 2020 at 09:25:26AM -0700, Randy Dunlap wrote:
On 8/21/20 8:28 AM, Tomer Samara wrote:
Remove BUG() from ion_sytem_heap.c
this fix the following checkpatch issue: Avoid crashing the kernel - try using WARN_ON & recovery code ratherthan BUG() or BUG_ON().
Signed-off-by: Tomer Samara tomersamara98@gmail.com
drivers/staging/android/ion/ion_system_heap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/staging/android/ion/ion_system_heap.c b/drivers/staging/android/ion/ion_system_heap.c index eac0632ab4e8..00d6154aec34 100644 --- a/drivers/staging/android/ion/ion_system_heap.c +++ b/drivers/staging/android/ion/ion_system_heap.c @@ -30,7 +30,7 @@ static int order_to_index(unsigned int order) for (i = 0; i < NUM_ORDERS; i++) if (order == orders[i]) return i;
- BUG();
- /* This is impossible. */ return -1;
}
Hi, Please explain why this is impossible.
If some caller calls order_to_index(5), it will return -1, yes?
I was happy enough with the comment as-is given that I suggested it. But an alternative comment could be "/* This is impossible. We always pass valid values to this function. */
Another option is to just change the BUG_ON() to a WARN_ON(). I feel like that communicates the same thing but makes checkpatch happy.
Actually earlier Greg pointed out that some systems have panic on warn so WARN_ON() doesn't work. Just add the comment.
regards, dan carpenter
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