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Subject[RFC PATCH 29/37] fs: list file types that support speculative faults.
Date
Add a speculative field to the vm_operations_struct, which indicates if
the associated file type supports speculative faults.

Initially this is set for files that implement fault() with filemap_fault().

Signed-off-by: Michel Lespinasse <michel@lespinasse.org>
---
fs/btrfs/file.c | 1 +
fs/cifs/file.c | 1 +
fs/fuse/file.c | 1 +
fs/nfs/file.c | 1 +
fs/ubifs/file.c | 1 +
fs/vboxsf/file.c | 1 +
include/linux/mm.h | 7 +++++++
mm/filemap.c | 1 +
8 files changed, 14 insertions(+)

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 0e155f013839..b31851271e51 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -2293,6 +2293,7 @@ static const struct vm_operations_struct btrfs_file_vm_ops = {
.fault = filemap_fault,
.map_pages = filemap_map_pages,
.page_mkwrite = btrfs_page_mkwrite,
+ .speculative = true,
};

static int btrfs_file_mmap(struct file *filp, struct vm_area_struct *vma)
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 042e24aad410..a0d5fbb25c62 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -4116,6 +4116,7 @@ static const struct vm_operations_struct cifs_file_vm_ops = {
.fault = filemap_fault,
.map_pages = filemap_map_pages,
.page_mkwrite = cifs_page_mkwrite,
+ .speculative = true,
};

int cifs_file_strict_mmap(struct file *file, struct vm_area_struct *vma)
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 8cccecb55fb8..c4874240d157 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -2354,6 +2354,7 @@ static const struct vm_operations_struct fuse_file_vm_ops = {
.fault = filemap_fault,
.map_pages = filemap_map_pages,
.page_mkwrite = fuse_page_mkwrite,
+ .speculative = true,
};

static int fuse_file_mmap(struct file *file, struct vm_area_struct *vma)
diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index 16ad5050e046..e653c6bc23ca 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -588,6 +588,7 @@ static const struct vm_operations_struct nfs_file_vm_ops = {
.fault = filemap_fault,
.map_pages = filemap_map_pages,
.page_mkwrite = nfs_vm_page_mkwrite,
+ .speculative = true,
};

static int nfs_need_check_write(struct file *filp, struct inode *inode,
diff --git a/fs/ubifs/file.c b/fs/ubifs/file.c
index 0e4b4be3aa26..3d97f1c3e9c7 100644
--- a/fs/ubifs/file.c
+++ b/fs/ubifs/file.c
@@ -1598,6 +1598,7 @@ static const struct vm_operations_struct ubifs_file_vm_ops = {
.fault = filemap_fault,
.map_pages = filemap_map_pages,
.page_mkwrite = ubifs_vm_page_mkwrite,
+ .speculative = true,
};

static int ubifs_file_mmap(struct file *file, struct vm_area_struct *vma)
diff --git a/fs/vboxsf/file.c b/fs/vboxsf/file.c
index c4ab5996d97a..e0a6a3af9cb9 100644
--- a/fs/vboxsf/file.c
+++ b/fs/vboxsf/file.c
@@ -146,6 +146,7 @@ static const struct vm_operations_struct vboxsf_file_vm_ops = {
.close = vboxsf_vma_close,
.fault = filemap_fault,
.map_pages = filemap_map_pages,
+ .speculative = true,
};

static int vboxsf_file_mmap(struct file *file, struct vm_area_struct *vma)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index f26490aff514..b4c0c10e434e 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -641,6 +641,13 @@ struct vm_operations_struct {
*/
struct page *(*find_special_page)(struct vm_area_struct *vma,
unsigned long addr);
+ /*
+ * speculative indicates that the vm_operations support
+ * speculative page faults. This allows ->fault and ->map_pages
+ * to be called with FAULT_FLAG_SPECULATIVE set; such calls will
+ * run within an rcu read locked section and with mmap lock not held.
+ */
+ bool speculative;
};

static inline void vma_init(struct vm_area_struct *vma, struct mm_struct *mm)
diff --git a/mm/filemap.c b/mm/filemap.c
index d496771749e6..b83040c672d3 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -3226,6 +3226,7 @@ const struct vm_operations_struct generic_file_vm_ops = {
.fault = filemap_fault,
.map_pages = filemap_map_pages,
.page_mkwrite = filemap_page_mkwrite,
+ .speculative = true,
};

/* This is used for a general mmap of a disk file */
--
2.20.1
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