https://github.com/torvalds/linux
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
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
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
Btrfs: pwrite blocked when writing from the mmaped buffer of the same page
Tip revision: 914ee29
inode.c
/*
* inode.c
*
* Copyright (C) 2001 Will Dyson <will_dyson@pobox.com>
*/
#include <linux/fs.h>
#include "befs.h"
#include "inode.h"
/*
Validates the correctness of the befs inode
Returns BEFS_OK if the inode should be used, otherwise
returns BEFS_BAD_INODE
*/
int
befs_check_inode(struct super_block *sb, befs_inode * raw_inode,
befs_blocknr_t inode)
{
u32 magic1 = fs32_to_cpu(sb, raw_inode->magic1);
befs_inode_addr ino_num = fsrun_to_cpu(sb, raw_inode->inode_num);
u32 flags = fs32_to_cpu(sb, raw_inode->flags);
/* check magic header. */
if (magic1 != BEFS_INODE_MAGIC1) {
befs_error(sb,
"Inode has a bad magic header - inode = %lu", inode);
return BEFS_BAD_INODE;
}
/*
* Sanity check2: inodes store their own block address. Check it.
*/
if (inode != iaddr2blockno(sb, &ino_num)) {
befs_error(sb, "inode blocknr field disagrees with vfs "
"VFS: %lu, Inode %lu",
inode, iaddr2blockno(sb, &ino_num));
return BEFS_BAD_INODE;
}
/*
* check flag
*/
if (!(flags & BEFS_INODE_IN_USE)) {
befs_error(sb, "inode is not used - inode = %lu", inode);
return BEFS_BAD_INODE;
}
return BEFS_OK;
}
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