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Message-ID: <20180226100611.sgw2rucvv6yhzn5y@quack2.suse.cz>
Date: Mon, 26 Feb 2018 11:06:11 +0100
From: Jan Kara <jack@...e.cz>
To: Dan Williams <dan.j.williams@...el.com>
Cc: linux-nvdimm@...ts.01.org,
"Darrick J. Wong" <darrick.wong@...cle.com>,
linux-kernel@...r.kernel.org, stable@...r.kernel.org,
linux-xfs@...r.kernel.org, linux-mm@...ck.org,
linux-fsdevel@...r.kernel.org,
kbuild test robot <fengguang.wu@...el.com>
Subject: Re: [PATCH v3 3/6] xfs, dax: introduce IS_FSDAX()
On Fri 23-02-18 16:43:27, Dan Williams wrote:
> Given that S_DAX is non-zero in the FS_DAX=n + DEV_DAX=y case, another
> mechanism besides the plain IS_DAX() check to compile out dead
> filesystem-dax code paths. Without IS_FSDAX() xfs will fail at link time
> with:
>
> ERROR: "dax_finish_sync_fault" [fs/xfs/xfs.ko] undefined!
> ERROR: "dax_iomap_fault" [fs/xfs/xfs.ko] undefined!
> ERROR: "dax_iomap_rw" [fs/xfs/xfs.ko] undefined!
>
> This compile failure was previously hidden by the fact that S_DAX was
> erroneously defined to '0' in the FS_DAX=n + DEV_DAX=y case.
>
> Cc: "Darrick J. Wong" <darrick.wong@...cle.com>
> Cc: linux-xfs@...r.kernel.org
> Cc: <stable@...r.kernel.org>
> Reported-by: kbuild test robot <fengguang.wu@...el.com>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>
As much as I appreciate that relying on compiler to optimize out dead
branches results in nicer looking code this is an example where it
backfires. Also having IS_DAX() and IS_FSDAX() doing almost the same, just
not exactly the same, is IMHO a recipe for confusion (e.g. a casual reader
could think why does ext4 get away with using IS_DAX while XFS has to use
IS_FSDAX?). So I'd just prefer to handle this as is usual in other kernel
areas - define empty stubs for all exported functions when CONFIG_FS_DAX is
not enabled. That way code can stay without ugly ifdefs and we don't have
to bother with IS_FSDAX vs IS_DAX distinction in filesystem code. Thoughts?
Honza
> ---
> fs/xfs/xfs_file.c | 14 +++++++-------
> fs/xfs/xfs_ioctl.c | 4 ++--
> fs/xfs/xfs_iomap.c | 6 +++---
> fs/xfs/xfs_reflink.c | 2 +-
> include/linux/fs.h | 2 ++
> 5 files changed, 15 insertions(+), 13 deletions(-)
>
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index 9ea08326f876..46a098b90fd0 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -288,7 +288,7 @@ xfs_file_read_iter(
> if (XFS_FORCED_SHUTDOWN(mp))
> return -EIO;
>
> - if (IS_DAX(inode))
> + if (IS_FSDAX(inode))
> ret = xfs_file_dax_read(iocb, to);
> else if (iocb->ki_flags & IOCB_DIRECT)
> ret = xfs_file_dio_aio_read(iocb, to);
> @@ -726,7 +726,7 @@ xfs_file_write_iter(
> if (XFS_FORCED_SHUTDOWN(ip->i_mount))
> return -EIO;
>
> - if (IS_DAX(inode))
> + if (IS_FSDAX(inode))
> ret = xfs_file_dax_write(iocb, from);
> else if (iocb->ki_flags & IOCB_DIRECT) {
> /*
> @@ -1045,7 +1045,7 @@ __xfs_filemap_fault(
> }
>
> xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
> - if (IS_DAX(inode)) {
> + if (IS_FSDAX(inode)) {
> pfn_t pfn;
>
> ret = dax_iomap_fault(vmf, pe_size, &pfn, NULL, &xfs_iomap_ops);
> @@ -1070,7 +1070,7 @@ xfs_filemap_fault(
> {
> /* DAX can shortcut the normal fault path on write faults! */
> return __xfs_filemap_fault(vmf, PE_SIZE_PTE,
> - IS_DAX(file_inode(vmf->vma->vm_file)) &&
> + IS_FSDAX(file_inode(vmf->vma->vm_file)) &&
> (vmf->flags & FAULT_FLAG_WRITE));
> }
>
> @@ -1079,7 +1079,7 @@ xfs_filemap_huge_fault(
> struct vm_fault *vmf,
> enum page_entry_size pe_size)
> {
> - if (!IS_DAX(file_inode(vmf->vma->vm_file)))
> + if (!IS_FSDAX(file_inode(vmf->vma->vm_file)))
> return VM_FAULT_FALLBACK;
>
> /* DAX can shortcut the normal fault path on write faults! */
> @@ -1124,12 +1124,12 @@ xfs_file_mmap(
> * We don't support synchronous mappings for non-DAX files. At least
> * until someone comes with a sensible use case.
> */
> - if (!IS_DAX(file_inode(filp)) && (vma->vm_flags & VM_SYNC))
> + if (!IS_FSDAX(file_inode(filp)) && (vma->vm_flags & VM_SYNC))
> return -EOPNOTSUPP;
>
> file_accessed(filp);
> vma->vm_ops = &xfs_file_vm_ops;
> - if (IS_DAX(file_inode(filp)))
> + if (IS_FSDAX(file_inode(filp)))
> vma->vm_flags |= VM_MIXEDMAP | VM_HUGEPAGE;
> return 0;
> }
> diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> index 89fb1eb80aae..234279ff66ce 100644
> --- a/fs/xfs/xfs_ioctl.c
> +++ b/fs/xfs/xfs_ioctl.c
> @@ -1108,9 +1108,9 @@ xfs_ioctl_setattr_dax_invalidate(
> }
>
> /* If the DAX state is not changing, we have nothing to do here. */
> - if ((fa->fsx_xflags & FS_XFLAG_DAX) && IS_DAX(inode))
> + if ((fa->fsx_xflags & FS_XFLAG_DAX) && IS_FSDAX(inode))
> return 0;
> - if (!(fa->fsx_xflags & FS_XFLAG_DAX) && !IS_DAX(inode))
> + if (!(fa->fsx_xflags & FS_XFLAG_DAX) && !IS_FSDAX(inode))
> return 0;
>
> /* lock, flush and invalidate mapping in preparation for flag change */
> diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
> index 66e1edbfb2b2..cf794d429aec 100644
> --- a/fs/xfs/xfs_iomap.c
> +++ b/fs/xfs/xfs_iomap.c
> @@ -241,7 +241,7 @@ xfs_iomap_write_direct(
> * the reserve block pool for bmbt block allocation if there is no space
> * left but we need to do unwritten extent conversion.
> */
> - if (IS_DAX(VFS_I(ip))) {
> + if (IS_FSDAX(VFS_I(ip))) {
> bmapi_flags = XFS_BMAPI_CONVERT | XFS_BMAPI_ZERO;
> if (imap->br_state == XFS_EXT_UNWRITTEN) {
> tflags |= XFS_TRANS_RESERVE;
> @@ -952,7 +952,7 @@ static inline bool imap_needs_alloc(struct inode *inode,
> return !nimaps ||
> imap->br_startblock == HOLESTARTBLOCK ||
> imap->br_startblock == DELAYSTARTBLOCK ||
> - (IS_DAX(inode) && imap->br_state == XFS_EXT_UNWRITTEN);
> + (IS_FSDAX(inode) && imap->br_state == XFS_EXT_UNWRITTEN);
> }
>
> static inline bool need_excl_ilock(struct xfs_inode *ip, unsigned flags)
> @@ -988,7 +988,7 @@ xfs_file_iomap_begin(
> return -EIO;
>
> if (((flags & (IOMAP_WRITE | IOMAP_DIRECT)) == IOMAP_WRITE) &&
> - !IS_DAX(inode) && !xfs_get_extsz_hint(ip)) {
> + !IS_FSDAX(inode) && !xfs_get_extsz_hint(ip)) {
> /* Reserve delalloc blocks for regular writeback. */
> return xfs_file_iomap_begin_delay(inode, offset, length, iomap);
> }
> diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
> index 270246943a06..a126e00e05e3 100644
> --- a/fs/xfs/xfs_reflink.c
> +++ b/fs/xfs/xfs_reflink.c
> @@ -1351,7 +1351,7 @@ xfs_reflink_remap_range(
> goto out_unlock;
>
> /* Don't share DAX file data for now. */
> - if (IS_DAX(inode_in) || IS_DAX(inode_out))
> + if (IS_FSDAX(inode_in) || IS_FSDAX(inode_out))
> goto out_unlock;
>
> ret = vfs_clone_file_prep_inodes(inode_in, pos_in, inode_out, pos_out,
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 79c413985305..a4310a95011b 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1909,6 +1909,8 @@ static inline bool sb_rdonly(const struct super_block *sb) { return sb->s_flags
> #define IS_WHITEOUT(inode) (S_ISCHR(inode->i_mode) && \
> (inode)->i_rdev == WHITEOUT_DEV)
>
> +#define IS_FSDAX(inode) (IS_ENABLED(CONFIG_FS_DAX) && IS_DAX(inode))
> +
> static inline bool HAS_UNMAPPED_ID(struct inode *inode)
> {
> return !uid_valid(inode->i_uid) || !gid_valid(inode->i_gid);
>
--
Jan Kara <jack@...e.com>
SUSE Labs, CR
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