Kernel/linux-stable
1
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git synced 2024-12-29 09:16:33 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

cramfs: Convert cramfs to read_folio

Browse Source 
This is a "weak" conversion which converts straight back to using pages.
A full conversion should be performed at some point, hopefully by
someone familiar with the filesystem.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
This commit is contained in:
Matthew Wilcox (Oracle) 2022-04-29 11:12:16 -04:00
parent 65c0d259cb
commit 5aab331ad6
2 changed files with 8 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
fs/cramfs/README
View File

@ -115,7 +115,7 @@ Block Size
(Block size in cramfs refers to the size of input data that is (Block size in cramfs refers to the size of input data that is
compressed at a time. It's intended to be somewhere around compressed at a time. It's intended to be somewhere around
PAGE_SIZE for cramfs_readpage's convenience.) PAGE_SIZE for cramfs_read_folio's convenience.)
The superblock ought to indicate the block size that the fs was The superblock ought to indicate the block size that the fs was
written for, since comments in <linux/pagemap.h> indicate that written for, since comments in <linux/pagemap.h> indicate that
@ -161,7 +161,7 @@ size. The options are:
PAGE_SIZE. PAGE_SIZE.
It's easy enough to change the kernel to use a smaller value than It's easy enough to change the kernel to use a smaller value than
PAGE_SIZE: just make cramfs_readpage read multiple blocks. PAGE_SIZE: just make cramfs_read_folio read multiple blocks.
The cost of option 1 is that kernels with a larger PAGE_SIZE The cost of option 1 is that kernels with a larger PAGE_SIZE
value don't get as good compression as they can. value don't get as good compression as they can.
@ -173,9 +173,9 @@ they don't mind their cramfs being inaccessible to kernels with
smaller PAGE_SIZE values. smaller PAGE_SIZE values.
Option 3 is easy to implement if we don't mind being CPU-inefficient: Option 3 is easy to implement if we don't mind being CPU-inefficient:
e.g. get readpage to decompress to a buffer of size MAX_BLKSIZE (which e.g. get read_folio to decompress to a buffer of size MAX_BLKSIZE (which
must be no larger than 32KB) and discard what it doesn't need. must be no larger than 32KB) and discard what it doesn't need.
Getting readpage to read into all the covered pages is harder. Getting read_folio to read into all the covered pages is harder.
The main advantage of option 3 over 1, 2, is better compression. The The main advantage of option 3 over 1, 2, is better compression. The
cost is greater complexity. Probably not worth it, but I hope someone cost is greater complexity. Probably not worth it, but I hope someone

7
fs/cramfs/inode.c
View File

@ -414,7 +414,7 @@ static int cramfs_physmem_mmap(struct file *file, struct vm_area_struct *vma)
/* /*
* Let's create a mixed map if we can't map it all. * Let's create a mixed map if we can't map it all.
* The normal paging machinery will take care of the * The normal paging machinery will take care of the
* unpopulated ptes via cramfs_readpage(). * unpopulated ptes via cramfs_read_folio().
*/ */
int i; int i;
vma->vm_flags |= VM_MIXEDMAP; vma->vm_flags |= VM_MIXEDMAP;
@ -814,8 +814,9 @@ static struct dentry *cramfs_lookup(struct inode *dir, struct dentry *dentry, un
return d_splice_alias(inode, dentry); return d_splice_alias(inode, dentry);
} }
static int cramfs_readpage(struct file *file, struct page *page) static int cramfs_read_folio(struct file *file, struct folio *folio)
{ {
struct page *page = &folio->page;
struct inode *inode = page->mapping->host; struct inode *inode = page->mapping->host;
u32 maxblock; u32 maxblock;
int bytes_filled; int bytes_filled;
@ -925,7 +926,7 @@ static int cramfs_readpage(struct file *file, struct page *page)
} }
static const struct address_space_operations cramfs_aops = { static const struct address_space_operations cramfs_aops = {
.readpage = cramfs_readpage .read_folio = cramfs_read_folio
}; };
/* /*