Re: [PATCH 1/7] ext2: tell DAX the size of allocation holes
From: Jan Kara <jack@suse.cz>
Date: 2016-08-16 09:10:25
Also in:
linux-ext4, linux-fsdevel, lkml, nvdimm
On Mon 15-08-16 13:09:12, Ross Zwisler wrote:
quoted hunk ↗ jump to hunk
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 <redacted> --- 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
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