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Date: Wed, 23 Sep 2015 00:42:06 -0400
From: Dan Williams <dan.j.williams@...el.com>
To: akpm@...ux-foundation.org
Cc: Jens Axboe <axboe@...nel.dk>, Boaz Harrosh <boaz@...xistor.com>,
linux-nvdimm@...ts.01.org, linux-kernel@...r.kernel.org,
linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
Ross Zwisler <ross.zwisler@...ux.intel.com>,
Christoph Hellwig <hch@....de>
Subject: [PATCH 10/15] block, dax: fix lifetime of in-kernel dax mappings
The DAX implementation needs to protect new calls to ->direct_access()
and usage of its return value against unbind of the underlying block
device. Use blk_dax_{get|put}() to either prevent blk_cleanup_queue()
from proceeding, or fail the dax_map_bh() if the request_queue is being
torn down.
Cc: Jens Axboe <axboe@...nel.dk>
Cc: Christoph Hellwig <hch@....de>
Cc: Boaz Harrosh <boaz@...xistor.com>
Cc: Ross Zwisler <ross.zwisler@...ux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
---
fs/dax.c | 131 ++++++++++++++++++++++++++++++++++++++++----------------------
1 file changed, 84 insertions(+), 47 deletions(-)
diff --git a/fs/dax.c b/fs/dax.c
index bcfb14bfc1e4..358eea39e982 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -63,12 +63,43 @@ int dax_clear_blocks(struct inode *inode, sector_t block, long size)
}
EXPORT_SYMBOL_GPL(dax_clear_blocks);
-static long dax_get_addr(struct buffer_head *bh, void __pmem **addr,
- unsigned blkbits)
+static void __pmem *__dax_map_bh(const struct buffer_head *bh, unsigned blkbits,
+ unsigned long *pfn, long *len)
{
- unsigned long pfn;
+ long rc;
+ void __pmem *addr;
+ struct block_device *bdev = bh->b_bdev;
+ struct request_queue *q = bdev->bd_queue;
sector_t sector = bh->b_blocknr << (blkbits - 9);
- return bdev_direct_access(bh->b_bdev, sector, addr, &pfn, bh->b_size);
+
+ rc = blk_dax_get(q);
+ if (rc < 0)
+ return (void __pmem *) ERR_PTR(rc);
+ rc = bdev_direct_access(bdev, sector, &addr, pfn, bh->b_size);
+ if (len)
+ *len = rc;
+ if (rc < 0) {
+ blk_dax_put(q);
+ return (void __pmem *) ERR_PTR(rc);
+ }
+ return addr;
+}
+
+static void __pmem *dax_map_bh(const struct buffer_head *bh, unsigned blkbits)
+{
+ unsigned long pfn;
+
+ return __dax_map_bh(bh, blkbits, &pfn, NULL);
+}
+
+static void dax_unmap_bh(const struct buffer_head *bh, void __pmem *addr)
+{
+ struct block_device *bdev = bh->b_bdev;
+ struct request_queue *q = bdev->bd_queue;
+
+ if (IS_ERR(addr))
+ return;
+ blk_dax_put(q);
}
/* the clear_pmem() calls are ordered by a wmb_pmem() in the caller */
@@ -104,15 +135,16 @@ static ssize_t dax_io(struct inode *inode, struct iov_iter *iter,
loff_t start, loff_t end, get_block_t get_block,
struct buffer_head *bh)
{
- ssize_t retval = 0;
- loff_t pos = start;
- loff_t max = start;
- loff_t bh_max = start;
- void __pmem *addr;
+ loff_t pos = start, max = start, bh_max = start;
+ int rw = iov_iter_rw(iter), rc;
+ long map_len = 0;
+ unsigned long pfn;
+ void __pmem *addr = NULL;
+ void __pmem *kmap = (void __pmem *) ERR_PTR(-EIO);
bool hole = false;
bool need_wmb = false;
- if (iov_iter_rw(iter) != WRITE)
+ if (rw == READ)
end = min(end, i_size_read(inode));
while (pos < end) {
@@ -127,9 +159,8 @@ static ssize_t dax_io(struct inode *inode, struct iov_iter *iter,
if (pos == bh_max) {
bh->b_size = PAGE_ALIGN(end - pos);
bh->b_state = 0;
- retval = get_block(inode, block, bh,
- iov_iter_rw(iter) == WRITE);
- if (retval)
+ rc = get_block(inode, block, bh, rw == WRITE);
+ if (rc)
break;
if (!buffer_size_valid(bh))
bh->b_size = 1 << blkbits;
@@ -141,21 +172,25 @@ static ssize_t dax_io(struct inode *inode, struct iov_iter *iter,
bh->b_size -= done;
}
- hole = iov_iter_rw(iter) != WRITE && !buffer_written(bh);
+ hole = rw == READ && !buffer_written(bh);
if (hole) {
addr = NULL;
size = bh->b_size - first;
} else {
- retval = dax_get_addr(bh, &addr, blkbits);
- if (retval < 0)
+ dax_unmap_bh(bh, kmap);
+ kmap = __dax_map_bh(bh, blkbits, &pfn, &map_len);
+ if (IS_ERR(kmap)) {
+ rc = PTR_ERR(kmap);
break;
+ }
+ addr = kmap;
if (buffer_unwritten(bh) || buffer_new(bh)) {
- dax_new_buf(addr, retval, first, pos,
- end);
+ dax_new_buf(addr, map_len, first, pos,
+ end);
need_wmb = true;
}
addr += first;
- size = retval - first;
+ size = map_len - first;
}
max = min(pos + size, end);
}
@@ -178,8 +213,9 @@ static ssize_t dax_io(struct inode *inode, struct iov_iter *iter,
if (need_wmb)
wmb_pmem();
+ dax_unmap_bh(bh, kmap);
- return (pos == start) ? retval : pos - start;
+ return (pos == start) ? rc : pos - start;
}
/**
@@ -274,21 +310,22 @@ static int copy_user_bh(struct page *to, struct buffer_head *bh,
void __pmem *vfrom;
void *vto;
- if (dax_get_addr(bh, &vfrom, blkbits) < 0)
- return -EIO;
+ vfrom = dax_map_bh(bh, blkbits);
+ if (IS_ERR(vfrom))
+ return PTR_ERR(vfrom);
vto = kmap_atomic(to);
copy_user_page(vto, (void __force *)vfrom, vaddr, to);
kunmap_atomic(vto);
+ dax_unmap_bh(bh, vfrom);
return 0;
}
static int dax_insert_mapping(struct inode *inode, struct buffer_head *bh,
struct vm_area_struct *vma, struct vm_fault *vmf)
{
- sector_t sector = bh->b_blocknr << (inode->i_blkbits - 9);
unsigned long vaddr = (unsigned long)vmf->virtual_address;
- void __pmem *addr;
unsigned long pfn;
+ void __pmem *addr;
pgoff_t size;
int error;
@@ -305,11 +342,9 @@ static int dax_insert_mapping(struct inode *inode, struct buffer_head *bh,
goto out;
}
- error = bdev_direct_access(bh->b_bdev, sector, &addr, &pfn, bh->b_size);
- if (error < 0)
- goto out;
- if (error < PAGE_SIZE) {
- error = -EIO;
+ addr = __dax_map_bh(bh, inode->i_blkbits, &pfn, NULL);
+ if (IS_ERR(addr)) {
+ error = PTR_ERR(addr);
goto out;
}
@@ -317,6 +352,7 @@ static int dax_insert_mapping(struct inode *inode, struct buffer_head *bh,
clear_pmem(addr, PAGE_SIZE);
wmb_pmem();
}
+ dax_unmap_bh(bh, addr);
error = vm_insert_mixed(vma, vaddr, pfn);
@@ -528,11 +564,8 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
unsigned blkbits = inode->i_blkbits;
unsigned long pmd_addr = address & PMD_MASK;
bool write = flags & FAULT_FLAG_WRITE;
- long length;
- void __pmem *kaddr;
pgoff_t size, pgoff;
- sector_t block, sector;
- unsigned long pfn;
+ sector_t block;
int result = 0;
/* Fall back to PTEs if we're going to COW */
@@ -557,8 +590,7 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
bh.b_size = PMD_SIZE;
i_mmap_lock_write(mapping);
- length = get_block(inode, block, &bh, write);
- if (length)
+ if (get_block(inode, block, &bh, write) != 0)
return VM_FAULT_SIGBUS;
/*
@@ -569,17 +601,17 @@ 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;
+ long length;
+ unsigned long pfn;
+ void __pmem *kaddr = __dax_map_bh(&bh, blkbits, &pfn, &length);
- length = bdev_direct_access(bh.b_bdev, sector, &kaddr, &pfn,
- bh.b_size);
- if (length < 0) {
+ if (IS_ERR(kaddr)) {
result = VM_FAULT_SIGBUS;
goto out;
}
+
if ((length < PMD_SIZE) || (pfn & PG_PMD_COLOUR))
goto fallback;
@@ -589,6 +621,7 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
count_vm_event(PGMAJFAULT);
mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
result |= VM_FAULT_MAJOR;
+ dax_unmap_bh(&bh, kaddr);
}
/*
@@ -635,12 +668,15 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
result = VM_FAULT_NOPAGE;
spin_unlock(ptl);
} else {
- length = bdev_direct_access(bh.b_bdev, sector, &kaddr, &pfn,
- bh.b_size);
- if (length < 0) {
+ long length;
+ unsigned long pfn;
+ void __pmem *kaddr = __dax_map_bh(&bh, blkbits, &pfn, &length);
+
+ if (IS_ERR(kaddr)) {
result = VM_FAULT_SIGBUS;
goto out;
}
+ dax_unmap_bh(&bh, kaddr);
if ((length < PMD_SIZE) || (pfn & PG_PMD_COLOUR))
goto fallback;
@@ -746,12 +782,13 @@ int dax_zero_page_range(struct inode *inode, loff_t from, unsigned length,
if (err < 0)
return err;
if (buffer_written(&bh)) {
- void __pmem *addr;
- err = dax_get_addr(&bh, &addr, inode->i_blkbits);
- if (err < 0)
- return err;
+ void __pmem *addr = dax_map_bh(&bh, inode->i_blkbits);
+
+ if (IS_ERR(addr))
+ return PTR_ERR(addr);
clear_pmem(addr + offset, length);
wmb_pmem();
+ dax_unmap_bh(&bh, addr);
}
return 0;
--
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