vfs: add the fadvise() file operation

This is going to be used by overlayfs and possibly useful
for other filesystems.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

3 files changed, 53 insertions, 33 deletions

diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
index ec2142c8dbd3..a6c6a8af48a2 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -885,6 +885,7 @@ struct file_operations {
         ssize_t (*copy_file_range)(struct file *, loff_t, struct file *, loff_t, size_t, unsigned int);
         int (*clone_file_range)(struct file *, loff_t, struct file *, loff_t, u64);
         int (*dedupe_file_range)(struct file *, loff_t, struct file *, loff_t, u64);
+        int (*fadvise)(struct file *, loff_t, loff_t, int);
 };
 
 Again, all methods are called without any locks being held, unless
@@ -965,6 +966,8 @@ otherwise noted.
   dedupe_file_range: called by the ioctl(2) system call for FIDEDUPERANGE
         command.
 
+  fadvise: possibly called by the fadvise64() system call.
+
 Note that the file operations are implemented by the specific
 filesystem in which the inode resides. When opening a device node
 (character or block special) most filesystems will call special
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 33322702c910..6c0b4a1c22ff 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1763,6 +1763,7 @@ struct file_operations {
                         u64);
         int (*dedupe_file_range)(struct file *, loff_t, struct file *, loff_t,
                         u64);
+        int (*fadvise)(struct file *, loff_t, loff_t, int);
 } __randomize_layout;
 
 struct inode_operations {
@@ -3459,4 +3460,8 @@ static inline bool dir_relax_shared(struct inode *inode)
 extern bool path_noexec(const struct path *path);
 extern void inode_nohighmem(struct inode *inode);
 
+/* mm/fadvise.c */
+extern int vfs_fadvise(struct file *file, loff_t offset, loff_t len,
+                       int advice);
+
 #endif /* _LINUX_FS_H */
diff --git a/mm/fadvise.c b/mm/fadvise.c
index 2d8376e3c640..2f59bac1cb77 100644
--- a/mm/fadvise.c
+++ b/mm/fadvise.c
@@ -27,9 +27,9 @@
  * deactivate the pages and clear PG_Referenced.
  */
 
-int ksys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
+static int generic_fadvise(struct file *file, loff_t offset, loff_t len,
+                           int advice)
 {
-        struct fd f = fdget(fd);
         struct inode *inode;
         struct address_space *mapping;
         struct backing_dev_info *bdi;
@@ -37,22 +37,14 @@ int ksys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
         pgoff_t start_index;
         pgoff_t end_index;
         unsigned long nrpages;
-        int ret = 0;
 
-        if (!f.file)
-                return -EBADF;
+        inode = file_inode(file);
+        if (S_ISFIFO(inode->i_mode))
+                return -ESPIPE;
 
-        inode = file_inode(f.file);
-        if (S_ISFIFO(inode->i_mode)) {
-                ret = -ESPIPE;
-                goto out;
-        }
-
-        mapping = f.file->f_mapping;
-        if (!mapping || len < 0) {
-                ret = -EINVAL;
-                goto out;
-        }
+        mapping = file->f_mapping;
+        if (!mapping || len < 0)
+                return -EINVAL;
 
         bdi = inode_to_bdi(mapping->host);
 
@@ -67,9 +59,9 @@ int ksys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
                         /* no bad return value, but ignore advice */
                         break;
                 default:
-                        ret = -EINVAL;
+                        return -EINVAL;
                 }
-                goto out;
+                return 0;
         }
 
         /*
@@ -85,21 +77,21 @@ int ksys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
 
         switch (advice) {
         case POSIX_FADV_NORMAL:
-                f.file->f_ra.ra_pages = bdi->ra_pages;
-                spin_lock(&f.file->f_lock);
-                f.file->f_mode &= ~FMODE_RANDOM;
-                spin_unlock(&f.file->f_lock);
+                file->f_ra.ra_pages = bdi->ra_pages;
+                spin_lock(&file->f_lock);
+                file->f_mode &= ~FMODE_RANDOM;
+                spin_unlock(&file->f_lock);
                 break;
         case POSIX_FADV_RANDOM:
-                spin_lock(&f.file->f_lock);
-                f.file->f_mode |= FMODE_RANDOM;
-                spin_unlock(&f.file->f_lock);
+                spin_lock(&file->f_lock);
+                file->f_mode |= FMODE_RANDOM;
+                spin_unlock(&file->f_lock);
                 break;
         case POSIX_FADV_SEQUENTIAL:
-                f.file->f_ra.ra_pages = bdi->ra_pages * 2;
-                spin_lock(&f.file->f_lock);
-                f.file->f_mode &= ~FMODE_RANDOM;
-                spin_unlock(&f.file->f_lock);
+                file->f_ra.ra_pages = bdi->ra_pages * 2;
+                spin_lock(&file->f_lock);
+                file->f_mode &= ~FMODE_RANDOM;
+                spin_unlock(&file->f_lock);
                 break;
         case POSIX_FADV_WILLNEED:
                 /* First and last PARTIAL page! */
@@ -115,8 +107,7 @@ int ksys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
                  * Ignore return value because fadvise() shall return
                  * success even if filesystem can't retrieve a hint,
                  */
-                force_page_cache_readahead(mapping, f.file, start_index,
-                                           nrpages);
+                force_page_cache_readahead(mapping, file, start_index, nrpages);
                 break;
         case POSIX_FADV_NOREUSE:
                 break;
@@ -183,9 +174,30 @@ int ksys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
                 }
                 break;
         default:
-                ret = -EINVAL;
+                return -EINVAL;
         }
-out:
+        return 0;
+}
+
+int vfs_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
+{
+        if (file->f_op->fadvise)
+                return file->f_op->fadvise(file, offset, len, advice);
+
+        return generic_fadvise(file, offset, len, advice);
+}
+EXPORT_SYMBOL(vfs_fadvise);
+
+int ksys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
+{
+        struct fd f = fdget(fd);
+        int ret;
+
+        if (!f.file)
+                return -EBADF;
+
+        ret = vfs_fadvise(f.file, offset, len, advice);
+
         fdput(f);
         return ret;
 }