* [PATCH v3 1/3] Revert "mm: take i_mmap_lock in unmap_mapping_range() for DAX"
2015-10-05 20:32 [PATCH v3 0/3] Revert locking changes in DAX for v4.3 Ross Zwisler
@ 2015-10-05 20:32 ` Ross Zwisler
2015-10-05 20:32 ` [PATCH v3 2/3] Revert "dax: fix race between simultaneous faults" Ross Zwisler
1 sibling, 0 replies; 3+ messages in thread
From: Ross Zwisler @ 2015-10-05 20:32 UTC (permalink / raw)
To: linux-kernel
Cc: Ross Zwisler, Alexander Viro, Matthew Wilcox, linux-fsdevel,
linux-mm, Andrew Morton, Dan Williams, Dave Chinner, Jan Kara,
Kirill A. Shutemov, linux-nvdimm
This reverts commits 46c043ede4711e8d598b9d63c5616c1fedb0605e
and 8346c416d17bf5b4ea1508662959bb62e73fd6a5.
The following two locking commits in the DAX code:
commit 843172978bb9 ("dax: fix race between simultaneous faults")
commit 46c043ede471 ("mm: take i_mmap_lock in unmap_mapping_range() for DAX")
introduced a number of deadlocks and other issues, and need to be
reverted for the v4.3 kernel. The list of issues in DAX after these
commits (some newly introduced by the commits, some preexisting) can be
found here:
https://lkml.org/lkml/2015/9/25/602
This revert keeps the PMEM API changes to the zeroing code in
__dax_pmd_fault(), which were added by this commit:
commit d77e92e270ed ("dax: update PMD fault handler with PMEM API")
Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
---
fs/dax.c | 50 ++++++++++++++++++--------------------------------
mm/memory.c | 11 +++++++++--
2 files changed, 27 insertions(+), 34 deletions(-)
diff --git a/fs/dax.c b/fs/dax.c
index bcfb14b..de3f53e 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -569,38 +569,6 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE)
goto fallback;
- sector = bh.b_blocknr << (blkbits - 9);
-
- if (buffer_unwritten(&bh) || buffer_new(&bh)) {
- int i;
-
- length = bdev_direct_access(bh.b_bdev, sector, &kaddr, &pfn,
- bh.b_size);
- if (length < 0) {
- result = VM_FAULT_SIGBUS;
- goto out;
- }
- if ((length < PMD_SIZE) || (pfn & PG_PMD_COLOUR))
- goto fallback;
-
- for (i = 0; i < PTRS_PER_PMD; i++)
- clear_pmem(kaddr + i * PAGE_SIZE, PAGE_SIZE);
- wmb_pmem();
- count_vm_event(PGMAJFAULT);
- mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
- result |= VM_FAULT_MAJOR;
- }
-
- /*
- * If we allocated new storage, make sure no process has any
- * zero pages covering this hole
- */
- if (buffer_new(&bh)) {
- i_mmap_unlock_write(mapping);
- unmap_mapping_range(mapping, pgoff << PAGE_SHIFT, PMD_SIZE, 0);
- i_mmap_lock_write(mapping);
- }
-
/*
* If a truncate happened while we were allocating blocks, we may
* leave blocks allocated to the file that are beyond EOF. We can't
@@ -615,6 +583,13 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
if ((pgoff | PG_PMD_COLOUR) >= size)
goto fallback;
+ /*
+ * If we allocated new storage, make sure no process has any
+ * zero pages covering this hole
+ */
+ if (buffer_new(&bh))
+ unmap_mapping_range(mapping, pgoff << PAGE_SHIFT, PMD_SIZE, 0);
+
if (!write && !buffer_mapped(&bh) && buffer_uptodate(&bh)) {
spinlock_t *ptl;
pmd_t entry;
@@ -635,6 +610,7 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
result = VM_FAULT_NOPAGE;
spin_unlock(ptl);
} else {
+ sector = bh.b_blocknr << (blkbits - 9);
length = bdev_direct_access(bh.b_bdev, sector, &kaddr, &pfn,
bh.b_size);
if (length < 0) {
@@ -644,6 +620,16 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
if ((length < PMD_SIZE) || (pfn & PG_PMD_COLOUR))
goto fallback;
+ if (buffer_unwritten(&bh) || buffer_new(&bh)) {
+ int i;
+ for (i = 0; i < PTRS_PER_PMD; i++)
+ clear_pmem(kaddr + i * PAGE_SIZE, PAGE_SIZE);
+ wmb_pmem();
+ count_vm_event(PGMAJFAULT);
+ mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
+ result |= VM_FAULT_MAJOR;
+ }
+
result |= vmf_insert_pfn_pmd(vma, address, pmd, pfn, write);
}
diff --git a/mm/memory.c b/mm/memory.c
index 9cb2747..5ec066f 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2426,10 +2426,17 @@ void unmap_mapping_range(struct address_space *mapping,
if (details.last_index < details.first_index)
details.last_index = ULONG_MAX;
- i_mmap_lock_write(mapping);
+
+ /*
+ * DAX already holds i_mmap_lock to serialise file truncate vs
+ * page fault and page fault vs page fault.
+ */
+ if (!IS_DAX(mapping->host))
+ i_mmap_lock_write(mapping);
if (unlikely(!RB_EMPTY_ROOT(&mapping->i_mmap)))
unmap_mapping_range_tree(&mapping->i_mmap, &details);
- i_mmap_unlock_write(mapping);
+ if (!IS_DAX(mapping->host))
+ i_mmap_unlock_write(mapping);
}
EXPORT_SYMBOL(unmap_mapping_range);
--
2.1.0
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
^ permalink raw reply related [flat|nested] 3+ messages in thread* [PATCH v3 2/3] Revert "dax: fix race between simultaneous faults"
2015-10-05 20:32 [PATCH v3 0/3] Revert locking changes in DAX for v4.3 Ross Zwisler
2015-10-05 20:32 ` [PATCH v3 1/3] Revert "mm: take i_mmap_lock in unmap_mapping_range() for DAX" Ross Zwisler
@ 2015-10-05 20:32 ` Ross Zwisler
1 sibling, 0 replies; 3+ messages in thread
From: Ross Zwisler @ 2015-10-05 20:32 UTC (permalink / raw)
To: linux-kernel
Cc: Ross Zwisler, Alexander Viro, Matthew Wilcox, linux-fsdevel,
linux-mm, Andrew Morton, Dan Williams, Dave Chinner, Jan Kara,
Kirill A. Shutemov, linux-nvdimm
This reverts commit 843172978bb92997310d2f7fbc172ece423cfc02.
The following two locking commits in the DAX code:
commit 843172978bb9 ("dax: fix race between simultaneous faults")
commit 46c043ede471 ("mm: take i_mmap_lock in unmap_mapping_range() for DAX")
introduced a number of deadlocks and other issues, and need to be
reverted for the v4.3 kernel. The list of issues in DAX after these
commits (some newly introduced by the commits, some preexisting) can be
found here:
https://lkml.org/lkml/2015/9/25/602
Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
---
fs/dax.c | 33 ++++++++++++++++-----------------
mm/memory.c | 11 +++--------
2 files changed, 19 insertions(+), 25 deletions(-)
diff --git a/fs/dax.c b/fs/dax.c
index de3f53e..f364c90 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -285,6 +285,7 @@ static int copy_user_bh(struct page *to, struct buffer_head *bh,
static int dax_insert_mapping(struct inode *inode, struct buffer_head *bh,
struct vm_area_struct *vma, struct vm_fault *vmf)
{
+ struct address_space *mapping = inode->i_mapping;
sector_t sector = bh->b_blocknr << (inode->i_blkbits - 9);
unsigned long vaddr = (unsigned long)vmf->virtual_address;
void __pmem *addr;
@@ -292,6 +293,8 @@ static int dax_insert_mapping(struct inode *inode, struct buffer_head *bh,
pgoff_t size;
int error;
+ i_mmap_lock_read(mapping);
+
/*
* Check truncate didn't happen while we were allocating a block.
* If it did, this block may or may not be still allocated to the
@@ -321,6 +324,8 @@ static int dax_insert_mapping(struct inode *inode, struct buffer_head *bh,
error = vm_insert_mixed(vma, vaddr, pfn);
out:
+ i_mmap_unlock_read(mapping);
+
return error;
}
@@ -382,17 +387,15 @@ int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
* from a read fault and we've raced with a truncate
*/
error = -EIO;
- goto unlock;
+ goto unlock_page;
}
- } else {
- i_mmap_lock_write(mapping);
}
error = get_block(inode, block, &bh, 0);
if (!error && (bh.b_size < PAGE_SIZE))
error = -EIO; /* fs corruption? */
if (error)
- goto unlock;
+ goto unlock_page;
if (!buffer_mapped(&bh) && !buffer_unwritten(&bh) && !vmf->cow_page) {
if (vmf->flags & FAULT_FLAG_WRITE) {
@@ -403,9 +406,8 @@ int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
if (!error && (bh.b_size < PAGE_SIZE))
error = -EIO;
if (error)
- goto unlock;
+ goto unlock_page;
} else {
- i_mmap_unlock_write(mapping);
return dax_load_hole(mapping, page, vmf);
}
}
@@ -417,15 +419,17 @@ int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
else
clear_user_highpage(new_page, vaddr);
if (error)
- goto unlock;
+ goto unlock_page;
vmf->page = page;
if (!page) {
+ i_mmap_lock_read(mapping);
/* Check we didn't race with truncate */
size = (i_size_read(inode) + PAGE_SIZE - 1) >>
PAGE_SHIFT;
if (vmf->pgoff >= size) {
+ i_mmap_unlock_read(mapping);
error = -EIO;
- goto unlock;
+ goto out;
}
}
return VM_FAULT_LOCKED;
@@ -461,8 +465,6 @@ int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
WARN_ON_ONCE(!(vmf->flags & FAULT_FLAG_WRITE));
}
- if (!page)
- i_mmap_unlock_write(mapping);
out:
if (error == -ENOMEM)
return VM_FAULT_OOM | major;
@@ -471,14 +473,11 @@ int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
return VM_FAULT_SIGBUS | major;
return VM_FAULT_NOPAGE | major;
- unlock:
+ unlock_page:
if (page) {
unlock_page(page);
page_cache_release(page);
- } else {
- i_mmap_unlock_write(mapping);
}
-
goto out;
}
EXPORT_SYMBOL(__dax_fault);
@@ -556,10 +555,10 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
block = (sector_t)pgoff << (PAGE_SHIFT - blkbits);
bh.b_size = PMD_SIZE;
- i_mmap_lock_write(mapping);
length = get_block(inode, block, &bh, write);
if (length)
return VM_FAULT_SIGBUS;
+ i_mmap_lock_read(mapping);
/*
* If the filesystem isn't willing to tell us the length of a hole,
@@ -634,11 +633,11 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
}
out:
+ i_mmap_unlock_read(mapping);
+
if (buffer_unwritten(&bh))
complete_unwritten(&bh, !(result & VM_FAULT_ERROR));
- i_mmap_unlock_write(mapping);
-
return result;
fallback:
diff --git a/mm/memory.c b/mm/memory.c
index 5ec066f..deb679c 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2427,16 +2427,11 @@ void unmap_mapping_range(struct address_space *mapping,
details.last_index = ULONG_MAX;
- /*
- * DAX already holds i_mmap_lock to serialise file truncate vs
- * page fault and page fault vs page fault.
- */
- if (!IS_DAX(mapping->host))
- i_mmap_lock_write(mapping);
+ /* DAX uses i_mmap_lock to serialise file truncate vs page fault */
+ i_mmap_lock_write(mapping);
if (unlikely(!RB_EMPTY_ROOT(&mapping->i_mmap)))
unmap_mapping_range_tree(&mapping->i_mmap, &details);
- if (!IS_DAX(mapping->host))
- i_mmap_unlock_write(mapping);
+ i_mmap_unlock_write(mapping);
}
EXPORT_SYMBOL(unmap_mapping_range);
--
2.1.0
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
^ permalink raw reply related [flat|nested] 3+ messages in thread