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23 October 2021, 00:29:24 UTC
Revision 914ee295af418e936ec20a08c1663eaabe4cd07a authored by Xin Zhong on 09 December 2010, 09:30:14 UTC, committed by Chris Mason on 10 December 2010, 21:29:10 UTC 
Btrfs: pwrite blocked when writing from the mmaped buffer of the same page
 
This problem is found in meego testing:
http://bugs.meego.com/show_bug.cgi?id=6672
A file in btrfs is mmaped and the mmaped buffer is passed to pwrite to write to the same page
of the same file. In btrfs_file_aio_write(), the pages is locked by prepare_pages(). So when
btrfs_copy_from_user() is called, page fault happens and the same page needs to be locked again
in filemap_fault(). The fix is to move iov_iter_fault_in_readable() before prepage_pages() to make page
fault happen before pages are locked. And also disable page fault in critical region in
btrfs_copy_from_user().

Reviewed-by: Yan, Zheng<zheng.z.yan@intel.com>
Signed-off-by: Zhong, Xin <xin.zhong@intel.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
1 parent f106e82
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Tip revision: 914ee295af418e936ec20a08c1663eaabe4cd07a authored by Xin Zhong on 09 December 2010, 09:30:14 UTC
Btrfs: pwrite blocked when writing from the mmaped buffer of the same page
Tip revision: 914ee29
datastream.h 
/*
 * datastream.h
 *
 */

struct buffer_head *befs_read_datastream(struct super_block *sb,
					 befs_data_stream * ds, befs_off_t pos,
					 uint * off);

int befs_fblock2brun(struct super_block *sb, befs_data_stream * data,
		     befs_blocknr_t fblock, befs_block_run * run);

size_t befs_read_lsymlink(struct super_block *sb, befs_data_stream * data,
			  void *buff, befs_off_t len);

befs_blocknr_t befs_count_blocks(struct super_block *sb, befs_data_stream * ds);

extern const befs_inode_addr BAD_IADDR;
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