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    SubjectRe: [PATCH v7 11/22] Replace ext2_clear_xip_target with dax_clear_blocks
    On Sun 23-03-14 15:08:37, Matthew Wilcox wrote:
    > This is practically generic code; other filesystems will want to call
    > it from other places, but there's nothing ext2-specific about it.
    >
    > Make it a little more generic by allowing it to take a count of the number
    > of bytes to zero rather than fixing it to a single page. Thanks to Dave
    > Hansen for suggesting that I need to call cond_resched() if zeroing more
    > than one page.
    Another day, some more review ;) Comments below.
    >
    > Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com>
    > ---
    > fs/dax.c | 34 ++++++++++++++++++++++++++++++++++
    > fs/ext2/inode.c | 8 +++++---
    > fs/ext2/xip.c | 23 -----------------------
    > fs/ext2/xip.h | 3 ---
    > include/linux/fs.h | 6 ++++++
    > 5 files changed, 45 insertions(+), 29 deletions(-)
    >
    > diff --git a/fs/dax.c b/fs/dax.c
    > index 7271be0..45a0a41 100644
    > --- a/fs/dax.c
    > +++ b/fs/dax.c
    > @@ -23,9 +23,43 @@
    > #include <linux/memcontrol.h>
    > #include <linux/mm.h>
    > #include <linux/mutex.h>
    > +#include <linux/sched.h>
    > #include <linux/uio.h>
    > #include <linux/vmstat.h>
    >
    > +int dax_clear_blocks(struct inode *inode, sector_t block, long size)
    > +{
    > + struct block_device *bdev = inode->i_sb->s_bdev;
    > + const struct block_device_operations *ops = bdev->bd_disk->fops;
    > + sector_t sector = block << (inode->i_blkbits - 9);
    > + unsigned long pfn;
    > +
    > + might_sleep();
    > + do {
    > + void *addr;
    > + long count = ops->direct_access(bdev, sector, &addr, &pfn,
    > + size);
    So do you assume blocksize == PAGE_SIZE here? If not, addr could be in
    the middle of the page AFAICT.

    > + if (count < 0)
    > + return count;
    > + while (count >= PAGE_SIZE) {
    > + clear_page(addr);
    > + addr += PAGE_SIZE;
    > + size -= PAGE_SIZE;
    > + count -= PAGE_SIZE;
    > + sector += PAGE_SIZE / 512;
    > + cond_resched();
    > + }
    > + if (count > 0) {
    > + memset(addr, 0, count);
    > + sector += count / 512;
    > + size -= count;
    > + }
    > + } while (size);
    > +
    > + return 0;
    > +}
    > +EXPORT_SYMBOL_GPL(dax_clear_blocks);
    > +
    > static long dax_get_addr(struct inode *inode, struct buffer_head *bh,
    > void **addr)
    > {
    > diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
    > index b156fe8..a9346a9 100644
    > --- a/fs/ext2/inode.c
    > +++ b/fs/ext2/inode.c
    > @@ -733,10 +733,12 @@ static int ext2_get_blocks(struct inode *inode,
    >
    > if (IS_DAX(inode)) {
    > /*
    > - * we need to clear the block
    > + * block must be initialised before we put it in the tree
    > + * so that it's not found by another thread before it's
    > + * initialised
    > */
    > - err = ext2_clear_xip_target (inode,
    > - le32_to_cpu(chain[depth-1].key));
    > + err = dax_clear_blocks(inode, le32_to_cpu(chain[depth-1].key),
    > + count << inode->i_blkbits);
    Umm 'count' looks wrong here. You want to clear only one block, don't
    you?

    > if (err) {
    > mutex_unlock(&ei->truncate_mutex);
    > goto cleanup;
    --
    Jan Kara <jack@suse.cz>
    SUSE Labs, CR


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