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Date: Tue, 16 Aug 2016 11:10:25 +0200 From: Jan Kara <jack@...e.cz> To: Ross Zwisler <ross.zwisler@...ux.intel.com> Cc: linux-kernel@...r.kernel.org, Theodore Ts'o <tytso@....edu>, Alexander Viro <viro@...iv.linux.org.uk>, Andreas Dilger <adilger.kernel@...ger.ca>, Andrew Morton <akpm@...ux-foundation.org>, Dan Williams <dan.j.williams@...el.com>, Dave Chinner <david@...morbit.com>, Jan Kara <jack@...e.com>, linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org, linux-mm@...ck.org, linux-nvdimm@...ts.01.org Subject: Re: [PATCH 1/7] ext2: tell DAX the size of allocation holes On Mon 15-08-16 13:09:12, Ross Zwisler wrote: > When DAX calls ext2_get_block() and the file offset points to a hole we > currently don't set bh_result->b_size. When we re-enable PMD faults DAX > will need bh_result->b_size to tell it the size of the hole so it can > decide whether to fault in a 4 KiB zero page or a 2 MiB zero page. > > For ext2 we always want DAX to use 4 KiB zero pages, so we just tell DAX > that all holes are 4 KiB in size. > > Signed-off-by: Ross Zwisler <ross.zwisler@...ux.intel.com> > --- > fs/ext2/inode.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c > index d5c7d09..c6d9763 100644 > --- a/fs/ext2/inode.c > +++ b/fs/ext2/inode.c > @@ -773,6 +773,12 @@ int ext2_get_block(struct inode *inode, sector_t iblock, struct buffer_head *bh_ > if (ret > 0) { > bh_result->b_size = (ret << inode->i_blkbits); > ret = 0; > + } else if (ret == 0 && IS_DAX(inode)) { I'd just drop the IS_DAX() check and set bh_result->b_size = 1 << inode->i_blkbits; IMO it's better to have things consistent between DAX & !DAX whenever possible. Honza > + /* > + * We have hit a hole. Tell DAX it is 4k in size so that it > + * uses PTE faults. > + */ > + bh_result->b_size = PAGE_SIZE; > } > return ret; > > -- > 2.9.0 > > -- Jan Kara <jack@...e.com> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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