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dax: fix lifetime of in-kernel dax mappings with dax_map_atomic() 

The DAX implementation needs to protect new calls to ->direct_access()
and usage of its return value against the driver for the underlying
block device being disabled.  Use blk_queue_enter()/blk_queue_exit() to
hold off blk_cleanup_queue() from proceeding, or otherwise fail new
mapping requests if the request_queue is being torn down.

This also introduces blk_dax_ctl to simplify the interface from fs/dax.c
through dax_map_atomic() to bdev_direct_access().

[willy@linux.intel.com: fix read() of a hole]
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Cc: Jan Kara <jack@suse.com>
Cc: Jens Axboe <axboe@fb.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Matthew Wilcox <willy@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Dan Williams 2016-01-15 16:55:59 -08:00 committed by Linus Torvalds
parent fe683adabf
commit b2e0d1625e
3 changed files with 149 additions and 87 deletions
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13
fs/block_dev.c
View File

@ -455,10 +455,7 @@ EXPORT_SYMBOL_GPL(bdev_write_page);
/**
* bdev_direct_access() - Get the address for directly-accessibly memory
* @bdev: The device containing the memory
* @sector: The offset within the device
* @addr: Where to put the address of the memory
* @pfn: The Page Frame Number for the memory
* @size: The number of bytes requested
* @dax: control and output parameters for ->direct_access
*
* If a block device is made up of directly addressable memory, this function
* will tell the caller the PFN and the address of the memory. The address
@ -469,10 +466,10 @@ EXPORT_SYMBOL_GPL(bdev_write_page);
* Return: negative errno if an error occurs, otherwise the number of bytes
* accessible at this address.
*/
long bdev_direct_access(struct block_device *bdev, sector_t sector,
void __pmem **addr, unsigned long *pfn, long size)
long bdev_direct_access(struct block_device *bdev, struct blk_dax_ctl *dax)
{
long avail;
sector_t sector = dax->sector;
long avail, size = dax->size;
const struct block_device_operations *ops = bdev->bd_disk->fops;
/*
@ -491,7 +488,7 @@ long bdev_direct_access(struct block_device *bdev, sector_t sector,
sector += get_start_sect(bdev);
if (sector % (PAGE_SIZE / 512))
return -EINVAL;
avail = ops->direct_access(bdev, sector, addr, pfn);
avail = ops->direct_access(bdev, sector, &dax->addr, &dax->pfn);
if (!avail)
return -ERANGE;
if (avail > 0 && avail & ~PAGE_MASK)

206
fs/dax.c
View File

@ -30,45 +30,65 @@
#include <linux/vmstat.h>
#include <linux/sizes.h>
static long dax_map_atomic(struct block_device *bdev, struct blk_dax_ctl *dax)
{
struct request_queue *q = bdev->bd_queue;
long rc = -EIO;
dax->addr = (void __pmem *) ERR_PTR(-EIO);
if (blk_queue_enter(q, true) != 0)
return rc;
rc = bdev_direct_access(bdev, dax);
if (rc < 0) {
dax->addr = (void __pmem *) ERR_PTR(rc);
blk_queue_exit(q);
return rc;
}
return rc;
}
static void dax_unmap_atomic(struct block_device *bdev,
const struct blk_dax_ctl *dax)
{
if (IS_ERR(dax->addr))
return;
blk_queue_exit(bdev->bd_queue);
}
/*
* dax_clear_blocks() is called from within transaction context from XFS,
* and hence this means the stack from this point must follow GFP_NOFS
* semantics for all operations.
*/
int dax_clear_blocks(struct inode *inode, sector_t block, long size)
int dax_clear_blocks(struct inode *inode, sector_t block, long _size)
{
struct block_device *bdev = inode->i_sb->s_bdev;
sector_t sector = block << (inode->i_blkbits - 9);
struct blk_dax_ctl dax = {
.sector = block << (inode->i_blkbits - 9),
.size = _size,
};
might_sleep();
do {
void __pmem *addr;
unsigned long pfn;
long count, sz;
count = bdev_direct_access(bdev, sector, &addr, &pfn, size);
count = dax_map_atomic(bdev, &dax);
if (count < 0)
return count;
sz = min_t(long, count, SZ_128K);
clear_pmem(addr, sz);
size -= sz;
sector += sz / 512;
clear_pmem(dax.addr, sz);
dax.size -= sz;
dax.sector += sz / 512;
dax_unmap_atomic(bdev, &dax);
cond_resched();
} while (size);
} while (dax.size);
wmb_pmem();
return 0;
}
EXPORT_SYMBOL_GPL(dax_clear_blocks);
static long dax_get_addr(struct buffer_head *bh, void __pmem **addr,
unsigned blkbits)
{
unsigned long pfn;
sector_t sector = bh->b_blocknr << (blkbits - 9);
return bdev_direct_access(bh->b_bdev, sector, addr, &pfn, bh->b_size);
}
/* the clear_pmem() calls are ordered by a wmb_pmem() in the caller */
static void dax_new_buf(void __pmem *addr, unsigned size, unsigned first,
loff_t pos, loff_t end)
@ -98,19 +118,29 @@ static bool buffer_size_valid(struct buffer_head *bh)
return bh->b_state != 0;
}
static sector_t to_sector(const struct buffer_head *bh,
const struct inode *inode)
{
sector_t sector = bh->b_blocknr << (inode->i_blkbits - 9);
return sector;
}
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;
bool hole = false;
bool need_wmb = false;
loff_t pos = start, max = start, bh_max = start;
bool hole = false, need_wmb = false;
struct block_device *bdev = NULL;
int rw = iov_iter_rw(iter), rc;
long map_len = 0;
struct blk_dax_ctl dax = {
.addr = (void __pmem *) ERR_PTR(-EIO),
};
if (iov_iter_rw(iter) != WRITE)
if (rw == READ)
end = min(end, i_size_read(inode));
while (pos < end) {
@ -125,13 +155,13 @@ 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;
bh_max = pos - first + bh->b_size;
bdev = bh->b_bdev;
} else {
unsigned done = bh->b_size -
(bh_max - (pos - first));
@ -139,47 +169,53 @@ 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_atomic(bdev, &dax);
dax.sector = to_sector(bh, inode);
dax.size = bh->b_size;
map_len = dax_map_atomic(bdev, &dax);
if (map_len < 0) {
rc = map_len;
break;
}
if (buffer_unwritten(bh) || buffer_new(bh)) {
dax_new_buf(addr, retval, first, pos,
end);
dax_new_buf(dax.addr, map_len, first,
pos, end);
need_wmb = true;
}
addr += first;
size = retval - first;
dax.addr += first;
size = map_len - first;
}
max = min(pos + size, end);
}
if (iov_iter_rw(iter) == WRITE) {
len = copy_from_iter_pmem(addr, max - pos, iter);
len = copy_from_iter_pmem(dax.addr, max - pos, iter);
need_wmb = true;
} else if (!hole)
len = copy_to_iter((void __force *)addr, max - pos,
len = copy_to_iter((void __force *) dax.addr, max - pos,
iter);
else
len = iov_iter_zero(max - pos, iter);
if (!len) {
retval = -EFAULT;
rc = -EFAULT;
break;
}
pos += len;
addr += len;
if (!IS_ERR(dax.addr))
dax.addr += len;
}
if (need_wmb)
wmb_pmem();
dax_unmap_atomic(bdev, &dax);
return (pos == start) ? retval : pos - start;
return (pos == start) ? rc : pos - start;
}
/**
@ -268,28 +304,35 @@ static int dax_load_hole(struct address_space *mapping, struct page *page,
return VM_FAULT_LOCKED;
}
static int copy_user_bh(struct page *to, struct buffer_head *bh,
unsigned blkbits, unsigned long vaddr)
static int copy_user_bh(struct page *to, struct inode *inode,
struct buffer_head *bh, unsigned long vaddr)
{
void __pmem *vfrom;
struct blk_dax_ctl dax = {
.sector = to_sector(bh, inode),
.size = bh->b_size,
};
struct block_device *bdev = bh->b_bdev;
void *vto;
if (dax_get_addr(bh, &vfrom, blkbits) < 0)
return -EIO;
if (dax_map_atomic(bdev, &dax) < 0)
return PTR_ERR(dax.addr);
vto = kmap_atomic(to);
copy_user_page(vto, (void __force *)vfrom, vaddr, to);
copy_user_page(vto, (void __force *)dax.addr, vaddr, to);
kunmap_atomic(vto);
dax_unmap_atomic(bdev, &dax);
return 0;
}
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;
unsigned long pfn;
struct address_space *mapping = inode->i_mapping;
struct block_device *bdev = bh->b_bdev;
struct blk_dax_ctl dax = {
.sector = to_sector(bh, inode),
.size = bh->b_size,
};
pgoff_t size;
int error;
@ -308,20 +351,18 @@ 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;
if (dax_map_atomic(bdev, &dax) < 0) {
error = PTR_ERR(dax.addr);
goto out;
}
if (buffer_unwritten(bh) || buffer_new(bh)) {
clear_pmem(addr, PAGE_SIZE);
clear_pmem(dax.addr, PAGE_SIZE);
wmb_pmem();
}
dax_unmap_atomic(bdev, &dax);
error = vm_insert_mixed(vma, vaddr, pfn);
error = vm_insert_mixed(vma, vaddr, dax.pfn);
out:
i_mmap_unlock_read(mapping);
@ -415,7 +456,7 @@ int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
if (vmf->cow_page) {
struct page *new_page = vmf->cow_page;
if (buffer_written(&bh))
error = copy_user_bh(new_page, &bh, blkbits, vaddr);
error = copy_user_bh(new_page, inode, &bh, vaddr);
else
clear_user_highpage(new_page, vaddr);
if (error)
@ -527,11 +568,9 @@ 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;
struct block_device *bdev;
pgoff_t size, pgoff;
sector_t block, sector;
unsigned long pfn;
sector_t block;
int result = 0;
/* dax pmd mappings are broken wrt gup and fork */
@ -559,9 +598,9 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
block = (sector_t)pgoff << (PAGE_SHIFT - blkbits);
bh.b_size = PMD_SIZE;
length = get_block(inode, block, &bh, write);
if (length)
if (get_block(inode, block, &bh, write) != 0)
return VM_FAULT_SIGBUS;
bdev = bh.b_bdev;
i_mmap_lock_read(mapping);
/*
@ -616,32 +655,40 @@ 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);
struct blk_dax_ctl dax = {
.sector = to_sector(&bh, inode),
.size = PMD_SIZE,
};
long length = dax_map_atomic(bdev, &dax);
if (length < 0) {
result = VM_FAULT_SIGBUS;
goto out;
}
if ((length < PMD_SIZE) || (pfn & PG_PMD_COLOUR))
if ((length < PMD_SIZE) || (dax.pfn & PG_PMD_COLOUR)) {
dax_unmap_atomic(bdev, &dax);
goto fallback;
}
/*
* TODO: teach vmf_insert_pfn_pmd() to support
* 'pte_special' for pmds
*/
if (pfn_valid(pfn))
if (pfn_valid(dax.pfn)) {
dax_unmap_atomic(bdev, &dax);
goto fallback;
}
if (buffer_unwritten(&bh) || buffer_new(&bh)) {
clear_pmem(kaddr, PMD_SIZE);
clear_pmem(dax.addr, PMD_SIZE);
wmb_pmem();
count_vm_event(PGMAJFAULT);
mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
result |= VM_FAULT_MAJOR;
}
dax_unmap_atomic(bdev, &dax);
result |= vmf_insert_pfn_pmd(vma, address, pmd, pfn, write);
result |= vmf_insert_pfn_pmd(vma, address, pmd, dax.pfn, write);
}
out:
@ -743,12 +790,17 @@ 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;
clear_pmem(addr + offset, length);
struct block_device *bdev = bh.b_bdev;
struct blk_dax_ctl dax = {
.sector = to_sector(&bh, inode),
.size = PAGE_CACHE_SIZE,
};
if (dax_map_atomic(bdev, &dax) < 0)
return PTR_ERR(dax.addr);
clear_pmem(dax.addr + offset, length);
wmb_pmem();
dax_unmap_atomic(bdev, &dax);
}
return 0;

17
include/linux/blkdev.h
View File

@ -1617,6 +1617,20 @@ static inline bool integrity_req_gap_front_merge(struct request *req,
#endif /* CONFIG_BLK_DEV_INTEGRITY */
/**
* struct blk_dax_ctl - control and output parameters for ->direct_access
* @sector: (input) offset relative to a block_device
* @addr: (output) kernel virtual address for @sector populated by driver
* @pfn: (output) page frame number for @addr populated by driver
* @size: (input) number of bytes requested
*/
struct blk_dax_ctl {
sector_t sector;
void __pmem *addr;
long size;
unsigned long pfn;
};
struct block_device_operations {
int (*open) (struct block_device *, fmode_t);
void (*release) (struct gendisk *, fmode_t);
@ -1643,8 +1657,7 @@ extern int __blkdev_driver_ioctl(struct block_device *, fmode_t, unsigned int,
extern int bdev_read_page(struct block_device *, sector_t, struct page *);
extern int bdev_write_page(struct block_device *, sector_t, struct page *,
struct writeback_control *);
extern long bdev_direct_access(struct block_device *, sector_t,
void __pmem **addr, unsigned long *pfn, long size);
extern long bdev_direct_access(struct block_device *, struct blk_dax_ctl *);
#else /* CONFIG_BLOCK */
struct block_device;