On Fri, Apr 25, 2025 at 06:38:41PM +0800, Chi Zhiling wrote:
> From: Chi Zhiling <chizhiling@xxxxxxxxxx>
>
> For unextending writes, we will only update the pagecache and extent.
> In this case, if our write occurs within a single block, that is,
> within a single folio, we don't need an exclusive lock to ensure the
> atomicity of the write, because we already have the folio lock.
>
> Signed-off-by: Chi Zhiling <chizhiling@xxxxxxxxxx>
> ---
> fs/xfs/xfs_file.c | 34 +++++++++++++++++++++++++++++++++-
> 1 file changed, 33 insertions(+), 1 deletion(-)
>
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index a6f214f57238..8eaa98464328 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -914,6 +914,27 @@ xfs_file_dax_write(
> return ret;
> }
>
> +#define offset_in_block(inode, p) ((unsigned long)(p) & (i_blocksize(inode) - 1))
Is it correct to cast an loff_t (s64) to unsigned long (u32 on i386)
here?
> +
> +static inline bool xfs_allow_concurrent(
static inline bool
xfs_allow_concurrent(
(separate lines style nit)
> + struct kiocb *iocb,
> + struct iov_iter *from)
> +{
> + struct inode *inode = iocb->ki_filp->f_mapping->host;
> +
> + /* Extending write? */
> + if (iocb->ki_flags & IOCB_APPEND ||
> + iocb->ki_pos >= i_size_read(inode))
> + return false;
> +
> + /* Exceeds a block range? */
> + if (iov_iter_count(from) > i_blocksize(inode) ||
> + offset_in_block(inode, iocb->ki_pos) + iov_iter_count(from) > i_blocksize(inode))
> + return false;
> +
> + return true;
> +}
...and since this helper only has one caller, maybe it should be named
xfs_buffered_write_iolock_mode and return the lock mode directly?
> +
> STATIC ssize_t
> xfs_file_buffered_write(
> struct kiocb *iocb,
> @@ -925,8 +946,12 @@ xfs_file_buffered_write(
> bool cleared_space = false;
> unsigned int iolock;
>
> + if (xfs_allow_concurrent(iocb, from))
> + iolock = XFS_IOLOCK_SHARED;
> + else
> + iolock = XFS_IOLOCK_EXCL;
> +
> write_retry:
> - iolock = XFS_IOLOCK_EXCL;
> ret = xfs_ilock_iocb_for_write(iocb, &iolock, false);
> if (ret)
> return ret;
> @@ -935,6 +960,13 @@ xfs_file_buffered_write(
> if (ret)
> goto out;
>
> + if (iolock == XFS_IOLOCK_SHARED &&
> + iocb->ki_pos + iov_iter_count(from) > i_size_read(inode)) {
> + xfs_iunlock(ip, iolock);
> + iolock = XFS_IOLOCK_EXCL;
> + goto write_retry;
> + }
> +
> trace_xfs_file_buffered_write(iocb, from);
> ret = iomap_file_buffered_write(iocb, from,
> &xfs_buffered_write_iomap_ops, NULL);
> --
> 2.43.0
>
>
