On Thu, 2017-10-19 at 19:39 -0700, Dan Williams wrote:
> Commit 128a37852234 "fs: fix data races on inode->i_flctx" converted
> checks of inode->i_flctx to use smp_load_acquire(), but it did not
> convert break_layout(). smp_load_acquire() includes a READ_ONCE(). There
> should be no functional difference since __break_lease repeats the
> sequence, but this is a clean up to unify all ->i_flctx lookups on a
> common pattern.
>
> Cc: Christoph Hellwig <hch@xxxxxx>
> Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
> Cc: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
> Cc: Jeff Layton <jlayton@xxxxxxxxxxxxxxx>
> Cc: "J. Bruce Fields" <bfields@xxxxxxxxxxxx>
> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> ---
> include/linux/fs.h | 10 ++++++----
> 1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 13dab191a23e..eace2c5396a7 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -2281,8 +2281,9 @@ static inline int break_lease(struct inode *inode, unsigned int mode)
> * could end up racing with tasks trying to set a new lease on this
> * file.
> */
> - smp_mb();
> - if (inode->i_flctx && !list_empty_careful(&inode->i_flctx->flc_lease))
> + struct file_lock_context *ctx = smp_load_acquire(&inode->i_flctx);
> +
> + if (ctx && !list_empty_careful(&ctx->flc_lease))
> return __break_lease(inode, mode, FL_LEASE);
> return 0;
> }
> @@ -2325,8 +2326,9 @@ static inline int break_deleg_wait(struct inode **delegated_inode)
>
> static inline int break_layout(struct inode *inode, bool wait)
> {
> - smp_mb();
> - if (inode->i_flctx && !list_empty_careful(&inode->i_flctx->flc_lease))
> + struct file_lock_context *ctx = smp_load_acquire(&inode->i_flctx);
> +
> + if (ctx && !list_empty_careful(&ctx->flc_lease))
> return __break_lease(inode,
> wait ? O_WRONLY : O_WRONLY | O_NONBLOCK,
> FL_LAYOUT);
>
Nice catch. This can go in independently of the rest of the patches in
the series, I think. I'll assume Andrew is picking this up since he's in
the "To:", but let me know if you need me to get it.
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
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