| Message ID | 4578bf3c7543f6f9a95b14a0523f2066f58ad43d.1527197312.git.osandov@fb.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 25.05.2018 00:41, Omar Sandoval wrote: > From: Omar Sandoval <osandov@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 <osandov@fb.com> Reviewed-by: Nikolay Borisov <nborisov@suse.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. >
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.