From: Omar Sandoval <osan...@fb.com>
The documentation for these functions is wrong in several ways:
- swap_activate() is called with the inode locked
- swap_activate() takes a swap_info_struct * and a sector_t *
- swap_activate() can also return a positive number of extents it added
itself
- swap_deactivate() does not return anything
Signed-off-by: Omar Sandoval <osan...@fb.com>
---
Documentation/filesystems/Locking | 17 +++++++----------
Documentation/filesystems/vfs.txt | 12 ++++++++----
2 files changed, 15 insertions(+), 14 deletions(-)
diff --git a/Documentation/filesystems/Locking
b/Documentation/filesystems/Locking
index 75d2d57e2c44..7f009e98fa3c 100644
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -211,8 +211,9 @@ prototypes:
int (*launder_page)(struct page *);
int (*is_partially_uptodate)(struct page *, unsigned long, unsigned
long);
int (*error_remove_page)(struct address_space *, struct page *);
- int (*swap_activate)(struct file *);
- int (*swap_deactivate)(struct file *);
+ int (*swap_activate)(struct swap_info_struct *, struct file *,
+ sector_t *);
+ void (*swap_deactivate)(struct file *);
locking rules:
All except set_page_dirty and freepage may block
@@ -236,8 +237,8 @@ putback_page: yes
launder_page: yes
is_partially_uptodate: yes
error_remove_page: yes
-swap_activate: no
-swap_deactivate: no
+swap_activate: yes
+swap_deactivate: no
->write_begin(), ->write_end() and ->readpage() may be called from
the request handler (/dev/loop).
@@ -334,14 +335,10 @@ cleaned, or an error value if not. Note that in order to
prevent the page
getting mapped back in and redirtied, it needs to be kept locked
across the entire operation.
- ->swap_activate will be called with a non-zero argument on
-files backing (non block device backed) swapfiles. A return value
-of zero indicates success, in which case this file can be used for
-backing swapspace. The swapspace operations will be proxied to the
-address space operations.
+ ->swap_activate is called from sys_swapon() with the inode locked.
->swap_deactivate() will be called in the sys_swapoff()
-path after ->swap_activate() returned success.
+path after ->swap_activate() returned success. The inode is not locked.
----------------------- file_lock_operations ------------------------------
prototypes:
diff --git a/Documentation/filesystems/vfs.txt
b/Documentation/filesystems/vfs.txt
index 5fd325df59e2..0149109d94d1 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -650,8 +650,9 @@ struct address_space_operations {
unsigned long);
void (*is_dirty_writeback) (struct page *, bool *, bool *);
int (*error_remove_page) (struct mapping *mapping, struct page *page);
- int (*swap_activate)(struct file *);
- int (*swap_deactivate)(struct file *);
+ int (*swap_activate)(struct swap_info_struct *, struct file *,
+ sector_t *);
+ void (*swap_deactivate)(struct file *);
};
writepage: called by the VM to write a dirty page to backing store.
@@ -828,8 +829,11 @@ struct address_space_operations {
swap_activate: Called when swapon is used on a file to allocate
space if necessary and pin the block lookup information in
- memory. A return value of zero indicates success,
- in which case this file can be used to back swapspace.
+ memory. If this returns zero, the swap system will call the address
+ space operations ->readpage() and ->direct_IO(). Alternatively, this
+ may call add_swap_extent() and return the number of extents added, in
+ which case the swap system will use the provided blocks directly
+ instead of going through the filesystem.
swap_deactivate: Called during swapoff on files where swap_activate
was successful.
--
2.17.0
--
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