On Thu 08-12-16 14:34:21, Dave Jiang wrote:
> Instead of passing in multiple parameters in the pmd_fault() handler,
> a vmf can be passed in just like a fault() handler. This will simplify
> code and remove the need for the actual pmd fault handlers to allocate a
> vmf. Related functions are also modified to do the same.
>
> Signed-off-by: Dave Jiang <dave.jiang@xxxxxxxxx>
> Reviewed-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
I like the idea however see below:
> @@ -1377,21 +1376,20 @@ int dax_iomap_pmd_fault(struct vm_area_struct *vma, unsigned long address,
> if (iomap.offset + iomap.length < pos + PMD_SIZE)
> goto unlock_entry;
>
> - vmf.pgoff = pgoff;
> - vmf.flags = flags;
> - vmf.gfp_mask = mapping_gfp_mask(mapping) | __GFP_IO;
> + vmf->pgoff = pgoff;
> + vmf->gfp_mask = mapping_gfp_mask(mapping) | __GFP_IO;
But now it's really unexpected that you change pgoff and gfp_mask because
that will propagate back to the caller and if we return VM_FAULT_FALLBACK
we may fault in wrong PTE because of this. So dax_iomap_pmd_fault() should
not modify the passed gfp_mask, just make its callers clear __GFP_FS from
it because *they* are responsible for acquiring locks / transactions that
block __GFP_FS allocations. They are also responsible for restoring
original gfp_mask once dax_iomap_pmd_fault() returns.
dax_iomap_pmd_fault() needs to modify pgoff however it must restore it to
the original value before it returns.
Otherwise the patch looks good to me.
Honza
>
> switch (iomap.type) {
> case IOMAP_MAPPED:
> - result = dax_pmd_insert_mapping(vma, pmd, &vmf, address,
> - &iomap, pos, write, &entry);
> + result = dax_pmd_insert_mapping(vma, vmf->pmd, vmf,
> + vmf->address, &iomap, pos, write, &entry);
> break;
> case IOMAP_UNWRITTEN:
> case IOMAP_HOLE:
> if (WARN_ON_ONCE(write))
> goto unlock_entry;
> - result = dax_pmd_load_hole(vma, pmd, &vmf, address, &iomap,
> - &entry);
> + result = dax_pmd_load_hole(vma, vmf->pmd, vmf, vmf->address,
> + &iomap, &entry);
> break;
> default:
> WARN_ON_ONCE(1);
> @@ -1417,12 +1415,11 @@ int dax_iomap_pmd_fault(struct vm_area_struct *vma, unsigned long address,
> }
> fallback:
> if (result == VM_FAULT_FALLBACK) {
> - split_huge_pmd(vma, pmd, address);
> + split_huge_pmd(vma, vmf->pmd, vmf->address);
> count_vm_event(THP_FAULT_FALLBACK);
> }
> out:
> - trace_dax_pmd_fault_done(inode, vma, address, flags, pgoff, max_pgoff,
> - result);
> + trace_dax_pmd_fault_done(inode, vma, vmf, max_pgoff, result);
> return result;
> }
> EXPORT_SYMBOL_GPL(dax_iomap_pmd_fault);
> diff --git a/fs/ext4/file.c b/fs/ext4/file.c
> index d663d3d..10b64ba 100644
> --- a/fs/ext4/file.c
> +++ b/fs/ext4/file.c
> @@ -275,21 +275,20 @@ static int ext4_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
> return result;
> }
>
> -static int ext4_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
> - pmd_t *pmd, unsigned int flags)
> +static int
> +ext4_dax_pmd_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
> {
> int result;
> struct inode *inode = file_inode(vma->vm_file);
> struct super_block *sb = inode->i_sb;
> - bool write = flags & FAULT_FLAG_WRITE;
> + bool write = vmf->flags & FAULT_FLAG_WRITE;
>
> if (write) {
> sb_start_pagefault(sb);
> file_update_time(vma->vm_file);
> }
> down_read(&EXT4_I(inode)->i_mmap_sem);
> - result = dax_iomap_pmd_fault(vma, addr, pmd, flags,
> - &ext4_iomap_ops);
> + result = dax_iomap_pmd_fault(vma, vmf, &ext4_iomap_ops);
> up_read(&EXT4_I(inode)->i_mmap_sem);
> if (write)
> sb_end_pagefault(sb);
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index d818c16..df0009f 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -1526,9 +1526,7 @@ xfs_filemap_fault(
> STATIC int
> xfs_filemap_pmd_fault(
> struct vm_area_struct *vma,
> - unsigned long addr,
> - pmd_t *pmd,
> - unsigned int flags)
> + struct vm_fault *vmf)
> {
> struct inode *inode = file_inode(vma->vm_file);
> struct xfs_inode *ip = XFS_I(inode);
> @@ -1539,16 +1537,16 @@ xfs_filemap_pmd_fault(
>
> trace_xfs_filemap_pmd_fault(ip);
>
> - if (flags & FAULT_FLAG_WRITE) {
> + if (vmf->flags & FAULT_FLAG_WRITE) {
> sb_start_pagefault(inode->i_sb);
> file_update_time(vma->vm_file);
> }
>
> xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
> - ret = dax_iomap_pmd_fault(vma, addr, pmd, flags, &xfs_iomap_ops);
> + ret = dax_iomap_pmd_fault(vma, vmf, &xfs_iomap_ops);
> xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
>
> - if (flags & FAULT_FLAG_WRITE)
> + if (vmf->flags & FAULT_FLAG_WRITE)
> sb_end_pagefault(inode->i_sb);
>
> return ret;
> diff --git a/include/linux/dax.h b/include/linux/dax.h
> index 6e36b11..9761c90 100644
> --- a/include/linux/dax.h
> +++ b/include/linux/dax.h
> @@ -71,16 +71,15 @@ static inline unsigned int dax_radix_order(void *entry)
> return PMD_SHIFT - PAGE_SHIFT;
> return 0;
> }
> -int dax_iomap_pmd_fault(struct vm_area_struct *vma, unsigned long address,
> - pmd_t *pmd, unsigned int flags, struct iomap_ops *ops);
> +int dax_iomap_pmd_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
> + struct iomap_ops *ops);
> #else
> static inline unsigned int dax_radix_order(void *entry)
> {
> return 0;
> }
> static inline int dax_iomap_pmd_fault(struct vm_area_struct *vma,
> - unsigned long address, pmd_t *pmd, unsigned int flags,
> - struct iomap_ops *ops)
> + struct vm_fault *vmf, struct iomap_ops *ops)
> {
> return VM_FAULT_FALLBACK;
> }
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 30f416a..aef645b 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -347,8 +347,7 @@ struct vm_operations_struct {
> void (*close)(struct vm_area_struct * area);
> int (*mremap)(struct vm_area_struct * area);
> int (*fault)(struct vm_area_struct *vma, struct vm_fault *vmf);
> - int (*pmd_fault)(struct vm_area_struct *, unsigned long address,
> - pmd_t *, unsigned int flags);
> + int (*pmd_fault)(struct vm_area_struct *vma, struct vm_fault *vmf);
> void (*map_pages)(struct vm_fault *vmf,
> pgoff_t start_pgoff, pgoff_t end_pgoff);
>
> diff --git a/include/trace/events/fs_dax.h b/include/trace/events/fs_dax.h
> index c3b0aae..a98665b 100644
> --- a/include/trace/events/fs_dax.h
> +++ b/include/trace/events/fs_dax.h
> @@ -8,9 +8,8 @@
>
> DECLARE_EVENT_CLASS(dax_pmd_fault_class,
> TP_PROTO(struct inode *inode, struct vm_area_struct *vma,
> - unsigned long address, unsigned int flags, pgoff_t pgoff,
> - pgoff_t max_pgoff, int result),
> - TP_ARGS(inode, vma, address, flags, pgoff, max_pgoff, result),
> + struct vm_fault *vmf, pgoff_t max_pgoff, int result),
> + TP_ARGS(inode, vma, vmf, max_pgoff, result),
> TP_STRUCT__entry(
> __field(unsigned long, ino)
> __field(unsigned long, vm_start)
> @@ -29,9 +28,9 @@ DECLARE_EVENT_CLASS(dax_pmd_fault_class,
> __entry->vm_start = vma->vm_start;
> __entry->vm_end = vma->vm_end;
> __entry->vm_flags = vma->vm_flags;
> - __entry->address = address;
> - __entry->flags = flags;
> - __entry->pgoff = pgoff;
> + __entry->address = vmf->address;
> + __entry->flags = vmf->flags;
> + __entry->pgoff = vmf->pgoff;
> __entry->max_pgoff = max_pgoff;
> __entry->result = result;
> ),
> @@ -54,9 +53,9 @@ DECLARE_EVENT_CLASS(dax_pmd_fault_class,
> #define DEFINE_PMD_FAULT_EVENT(name) \
> DEFINE_EVENT(dax_pmd_fault_class, name, \
> TP_PROTO(struct inode *inode, struct vm_area_struct *vma, \
> - unsigned long address, unsigned int flags, pgoff_t pgoff, \
> + struct vm_fault *vmf, \
> pgoff_t max_pgoff, int result), \
> - TP_ARGS(inode, vma, address, flags, pgoff, max_pgoff, result))
> + TP_ARGS(inode, vma, vmf, max_pgoff, result))
>
> DEFINE_PMD_FAULT_EVENT(dax_pmd_fault);
> DEFINE_PMD_FAULT_EVENT(dax_pmd_fault_done);
> diff --git a/mm/memory.c b/mm/memory.c
> index e37250f..8ec36cf 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3447,8 +3447,7 @@ static int create_huge_pmd(struct vm_fault *vmf)
> if (vma_is_anonymous(vma))
> return do_huge_pmd_anonymous_page(vmf);
> if (vma->vm_ops->pmd_fault)
> - return vma->vm_ops->pmd_fault(vma, vmf->address, vmf->pmd,
> - vmf->flags);
> + return vma->vm_ops->pmd_fault(vma, vmf);
> return VM_FAULT_FALLBACK;
> }
>
> @@ -3457,8 +3456,7 @@ static int wp_huge_pmd(struct vm_fault *vmf, pmd_t orig_pmd)
> if (vma_is_anonymous(vmf->vma))
> return do_huge_pmd_wp_page(vmf, orig_pmd);
> if (vmf->vma->vm_ops->pmd_fault)
> - return vmf->vma->vm_ops->pmd_fault(vmf->vma, vmf->address,
> - vmf->pmd, vmf->flags);
> + return vmf->vma->vm_ops->pmd_fault(vmf->vma, vmf);
>
> /* COW handled on pte level: split pmd */
> VM_BUG_ON_VMA(vmf->vma->vm_flags & VM_SHARED, vmf->vma);
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
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