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Commit 069c77bc authored by Jan Kara's avatar Jan Kara Committed by Vishal Verma
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dax: Remove zeroing from dax_io() 



All the filesystems are now zeroing blocks themselves for DAX IO to avoid
races between dax_io() and dax_fault(). Remove the zeroing code from
dax_io() and add warning to catch the case when somebody unexpectedly
returns new or unwritten buffer.

Reviewed-by: default avatarRoss Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarVishal Verma <vishal.l.verma@intel.com>
parent 2b10945c

fs/dax.c

+10 −18
Original line number Diff line number Diff line
@@ -119,18 +119,6 @@ int dax_clear_sectors(struct block_device *bdev, sector_t _sector, long _size) 
}

EXPORT_SYMBOL_GPL(dax_clear_sectors);



/* 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)

{

	loff_t final = end - pos + first; /* The final byte of the buffer */



	if (first > 0)

		clear_pmem(addr, first);

	if (final < size)

		clear_pmem(addr + final, size - final);

}



static bool buffer_written(struct buffer_head *bh)

{

	return buffer_mapped(bh) && !buffer_unwritten(bh);
@@ -169,6 +157,9 @@ static ssize_t dax_io(struct inode *inode, struct iov_iter *iter, 
	struct blk_dax_ctl dax = {

		.addr = (void __pmem *) ERR_PTR(-EIO),

	};

	unsigned blkbits = inode->i_blkbits;

	sector_t file_blks = (i_size_read(inode) + (1 << blkbits) - 1)

								>> blkbits;



	if (rw == READ)

		end = min(end, i_size_read(inode));
@@ -176,7 +167,6 @@ static ssize_t dax_io(struct inode *inode, struct iov_iter *iter, 
	while (pos < end) {

		size_t len;

		if (pos == max) {

			unsigned blkbits = inode->i_blkbits;

			long page = pos >> PAGE_SHIFT;

			sector_t block = page << (PAGE_SHIFT - blkbits);

			unsigned first = pos - (block << blkbits);
@@ -192,6 +182,13 @@ static ssize_t dax_io(struct inode *inode, struct iov_iter *iter, 
					bh->b_size = 1 << blkbits;

				bh_max = pos - first + bh->b_size;

				bdev = bh->b_bdev;

				/*

				 * We allow uninitialized buffers for writes

				 * beyond EOF as those cannot race with faults

				 */

				WARN_ON_ONCE(

					(buffer_new(bh) && block < file_blks) ||

					(rw == WRITE && buffer_unwritten(bh)));

			} else {

				unsigned done = bh->b_size -

						(bh_max - (pos - first));
@@ -211,11 +208,6 @@ static ssize_t dax_io(struct inode *inode, struct iov_iter *iter, 
					rc = map_len;

					break;

				}

				if (buffer_unwritten(bh) || buffer_new(bh)) {

					dax_new_buf(dax.addr, map_len, first,

							pos, end);

					need_wmb = true;

				}

				dax.addr += first;

				size = map_len - first;

			}