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Merge branch 'xfs-mmap-lock' into for-next

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This commit is contained in:
Dave Chinner 2015-02-24 10:27:47 +11:00
commit 88e8fda99a
8 changed files with 216 additions and 113 deletions
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63
fs/xfs/xfs_iops.c
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@ -771,6 +771,7 @@ xfs_setattr_size(
return error;
ASSERT(xfs_isilocked(ip, XFS_IOLOCK_EXCL));
ASSERT(xfs_isilocked(ip, XFS_MMAPLOCK_EXCL));
ASSERT(S_ISREG(ip->i_d.di_mode));
ASSERT((iattr->ia_valid & (ATTR_UID|ATTR_GID|ATTR_ATIME|ATTR_ATIME_SET|
ATTR_MTIME_SET|ATTR_KILL_PRIV|ATTR_TIMES_SET)) == 0);
@ -834,55 +835,27 @@ xfs_setattr_size(
inode_dio_wait(inode);
/*
* Do all the page cache truncate work outside the transaction context
* as the "lock" order is page lock->log space reservation. i.e.
* locking pages inside the transaction can ABBA deadlock with
* writeback. We have to do the VFS inode size update before we truncate
* the pagecache, however, to avoid racing with page faults beyond the
* new EOF they are not serialised against truncate operations except by
* page locks and size updates.
* We've already locked out new page faults, so now we can safely remove
* pages from the page cache knowing they won't get refaulted until we
* drop the XFS_MMAP_EXCL lock after the extent manipulations are
* complete. The truncate_setsize() call also cleans partial EOF page
* PTEs on extending truncates and hence ensures sub-page block size
* filesystems are correctly handled, too.
*
* Hence we are in a situation where a truncate can fail with ENOMEM
* from xfs_trans_reserve(), but having already truncated the in-memory
* version of the file (i.e. made user visible changes). There's not
* much we can do about this, except to hope that the caller sees ENOMEM
* and retries the truncate operation.
* We have to do all the page cache truncate work outside the
* transaction context as the "lock" order is page lock->log space
* reservation as defined by extent allocation in the writeback path.
* Hence a truncate can fail with ENOMEM from xfs_trans_reserve(), but
* having already truncated the in-memory version of the file (i.e. made
* user visible changes). There's not much we can do about this, except
* to hope that the caller sees ENOMEM and retries the truncate
* operation.
*/
error = block_truncate_page(inode->i_mapping, newsize, xfs_get_blocks);
if (error)
return error;
truncate_setsize(inode, newsize);
/*
* The "we can't serialise against page faults" pain gets worse.
*
* If the file is mapped then we have to clean the page at the old EOF
* when extending the file. Extending the file can expose changes the
* underlying page mapping (e.g. from beyond EOF to a hole or
* unwritten), and so on the next attempt to write to that page we need
* to remap it for write. i.e. we need .page_mkwrite() to be called.
* Hence we need to clean the page to clean the pte and so a new write
* fault will be triggered appropriately.
*
* If we do it before we change the inode size, then we can race with a
* page fault that maps the page with exactly the same problem. If we do
* it after we change the file size, then a new page fault can come in
* and allocate space before we've run the rest of the truncate
* transaction. That's kinda grotesque, but it's better than have data
* over a hole, and so that's the lesser evil that has been chosen here.
*
* The real solution, however, is to have some mechanism for locking out
* page faults while a truncate is in progress.
*/
if (newsize > oldsize && mapping_mapped(VFS_I(ip)->i_mapping)) {
error = filemap_write_and_wait_range(
VFS_I(ip)->i_mapping,
round_down(oldsize, PAGE_CACHE_SIZE),
round_up(oldsize, PAGE_CACHE_SIZE) - 1);
if (error)
return error;
}
tp = xfs_trans_alloc(mp, XFS_TRANS_SETATTR_SIZE);
error = xfs_trans_reserve(tp, &M_RES(mp)->tr_itruncate, 0, 0);
if (error)
@ -981,8 +954,12 @@ xfs_vn_setattr(
xfs_ilock(ip, iolock);
error = xfs_break_layouts(dentry->d_inode, &iolock);
if (!error)
if (!error) {
xfs_ilock(ip, XFS_MMAPLOCK_EXCL);
iolock |= XFS_MMAPLOCK_EXCL;
error = xfs_setattr_size(ip, iattr);
}
xfs_iunlock(ip, iolock);
} else {
error = xfs_setattr_nonsize(ip, iattr, 0);