On Tue 17-11-15 12:16:14, Dan Williams wrote: > Currently dax mappings survive block_device shutdown. While page cache > pages are permitted to be read/written after the block_device is torn > down this is not acceptable in the dax case as all media access must end > when the device is disabled. The pfn backing a dax mapping is permitted > to be invalidated after bdev shutdown and this is indeed the case with > brd. > > When a dax capable block_device driver calls del_gendisk() in its > shutdown path, or a filesystem evicts an inode it needs to ensure that > all the pfns that had been mapped via bdev_direct_access() are unmapped. > This is different than the pagecache backed case where > truncate_inode_pages() is sufficient to end I/O to pages mapped to a > dying inode. > > Since dax bypasses the page cache we need to unmap in addition to > truncating pages. Also, since dax mappings are not accounted in the > mapping radix we uncoditionally truncate all inodes with the S_DAX flag. > Likely when we add support for dynamic dax enable/disable control we'll > have infrastructure to detect if the inode is unmapped and can skip the > truncate. > > Cc: <stable@xxxxxxxxxxxxxxx> > Cc: Jan Kara <jack@xxxxxxxx> > Cc: Dave Chinner <david@xxxxxxxxxxxxx> > Cc: Matthew Wilcox <willy@xxxxxxxxxxxxxxx> > Cc: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx> > Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx> > --- > fs/inode.c | 27 +++++++++++++++++++++++++++ > mm/truncate.c | 13 +++++++++++-- > 2 files changed, 38 insertions(+), 2 deletions(-) ... > @@ -433,7 +434,15 @@ void truncate_inode_pages_final(struct address_space *mapping) > spin_lock_irq(&mapping->tree_lock); > spin_unlock_irq(&mapping->tree_lock); > > - truncate_inode_pages(mapping, 0); > + /* > + * In the case of DAX we also need to unmap the inode > + * since the pfn backing the mapping may be invalidated > + * after this returns > + */ > + if (IS_DAX(inode)) > + truncate_pagecache(inode, 0); > + else > + truncate_inode_pages(mapping, 0); > } Hum, I don't get this. truncate_inode_pages_final() gets called when inode has no more users. So there are no mappings of the inode. So how could truncate_pagecache() possibly make a difference? Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
