On Thu 21-01-16 10:46:03, Ross Zwisler wrote:
> Fix the way that DAX PMD radix tree entries are handled. With this patch
> we now check to see if a PMD entry exists in the radix tree on write, even
> if we are just trying to insert a PTE. If it exists, we dirty that instead
> of inserting our own PTE entry.
>
> Fix a bug in the PMD path in dax_writeback_mapping_range() where we were
> previously passing a loff_t into radix_tree_lookup instead of a pgoff_t.
Ah, good catch!
> Account for the fact that multiple fsync/msync operations may be happening
> at the same time and don't flush entries that are beyond end_index.
>
> Signed-off-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
Just one nit below. You can add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
> ---
> fs/dax.c | 39 +++++++++++++++++++++++++++------------
> 1 file changed, 27 insertions(+), 12 deletions(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index 55ae394..afacc30 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
...
> @@ -460,31 +468,33 @@ int dax_writeback_mapping_range(struct address_space *mapping, loff_t start,
> {
> struct inode *inode = mapping->host;
> struct block_device *bdev = inode->i_sb->s_bdev;
> + pgoff_t start_index, end_index, pmd_index;
> pgoff_t indices[PAGEVEC_SIZE];
> - pgoff_t start_page, end_page;
> struct pagevec pvec;
> - void *entry;
> + bool done = false;
> int i, ret = 0;
> + void *entry;
>
> if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT))
> return -EIO;
>
> + start_index = start >> PAGE_CACHE_SHIFT;
> + end_index = end >> PAGE_CACHE_SHIFT;
> + pmd_index = DAX_PMD_INDEX(start_index);
> +
> rcu_read_lock();
> - entry = radix_tree_lookup(&mapping->page_tree, start & PMD_MASK);
> + entry = radix_tree_lookup(&mapping->page_tree, pmd_index);
> rcu_read_unlock();
>
> /* see if the start of our range is covered by a PMD entry */
> - if (entry && RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
> - start &= PMD_MASK;
> -
> - start_page = start >> PAGE_CACHE_SHIFT;
> - end_page = end >> PAGE_CACHE_SHIFT;
> + if (RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
Don't you miss a check that entry != NULL? I agree that RADIX_DAX_TYPE(NULL)
is != from RADIX_DAX_PMD so it works as desired but it looks a bit
dangerous.
Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
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