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xfs: teach xfile to pass back direct-map pages to caller

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Certain xfile array operations (such as sorting) can be sped up quite a
bit by allowing xfile users to grab a page to bulk-read the records
contained within it.  Create helper methods to facilitate this.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Kent Overstreet <kent.overstreet@linux.dev>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
This commit is contained in:
Darrick J. Wong 2023-08-10 07:48:05 -07:00
parent c390c64503
commit 137db333b2
3 changed files with 120 additions and 0 deletions
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2
fs/xfs/scrub/trace.h
View File

@ -821,6 +821,8 @@ DEFINE_EVENT(xfile_class, name, \
DEFINE_XFILE_EVENT(xfile_pread);
DEFINE_XFILE_EVENT(xfile_pwrite);
DEFINE_XFILE_EVENT(xfile_seek_data);
DEFINE_XFILE_EVENT(xfile_get_page);
DEFINE_XFILE_EVENT(xfile_put_page);
TRACE_EVENT(xfarray_create,
TP_PROTO(struct xfarray *xfa, unsigned long long required_capacity),

108
fs/xfs/scrub/xfile.c
View File

@ -310,3 +310,111 @@ xfile_stat(
statbuf->bytes = ks.blocks << SECTOR_SHIFT;
return 0;
}
/*
* Grab the (locked) page for a memory object. The object cannot span a page
* boundary. Returns 0 (and a locked page) if successful, -ENOTBLK if we
* cannot grab the page, or the usual negative errno.
*/
int
xfile_get_page(
struct xfile *xf,
loff_t pos,
unsigned int len,
struct xfile_page *xfpage)
{
struct inode *inode = file_inode(xf->file);
struct address_space *mapping = inode->i_mapping;
const struct address_space_operations *aops = mapping->a_ops;
struct page *page = NULL;
void *fsdata = NULL;
loff_t key = round_down(pos, PAGE_SIZE);
unsigned int pflags;
int error;
if (inode->i_sb->s_maxbytes - pos < len)
return -ENOMEM;
if (len > PAGE_SIZE - offset_in_page(pos))
return -ENOTBLK;
trace_xfile_get_page(xf, pos, len);
pflags = memalloc_nofs_save();
/*
* We call write_begin directly here to avoid all the freezer
* protection lock-taking that happens in the normal path. shmem
* doesn't support fs freeze, but lockdep doesn't know that and will
* trip over that.
*/
error = aops->write_begin(NULL, mapping, key, PAGE_SIZE, &page,
&fsdata);
if (error)
goto out_pflags;
/* We got the page, so make sure we push out EOF. */
if (i_size_read(inode) < pos + len)
i_size_write(inode, pos + len);
/*
* If the page isn't up to date, fill it with zeroes before we hand it
* to the caller and make sure the backing store will hold on to them.
*/
if (!PageUptodate(page)) {
void *kaddr;
kaddr = kmap_local_page(page);
memset(kaddr, 0, PAGE_SIZE);
kunmap_local(kaddr);
SetPageUptodate(page);
}
/*
* Mark each page dirty so that the contents are written to some
* backing store when we drop this buffer, and take an extra reference
* to prevent the xfile page from being swapped or removed from the
* page cache by reclaim if the caller unlocks the page.
*/
set_page_dirty(page);
get_page(page);
xfpage->page = page;
xfpage->fsdata = fsdata;
xfpage->pos = key;
out_pflags:
memalloc_nofs_restore(pflags);
return error;
}
/*
* Release the (locked) page for a memory object. Returns 0 or a negative
* errno.
*/
int
xfile_put_page(
struct xfile *xf,
struct xfile_page *xfpage)
{
struct inode *inode = file_inode(xf->file);
struct address_space *mapping = inode->i_mapping;
const struct address_space_operations *aops = mapping->a_ops;
unsigned int pflags;
int ret;
trace_xfile_put_page(xf, xfpage->pos, PAGE_SIZE);
/* Give back the reference that we took in xfile_get_page. */
put_page(xfpage->page);
pflags = memalloc_nofs_save();
ret = aops->write_end(NULL, mapping, xfpage->pos, PAGE_SIZE, PAGE_SIZE,
xfpage->page, xfpage->fsdata);
memalloc_nofs_restore(pflags);
memset(xfpage, 0, sizeof(struct xfile_page));
if (ret < 0)
return ret;
if (ret != PAGE_SIZE)
return -EIO;
return 0;
}

10
fs/xfs/scrub/xfile.h
View File

@ -6,6 +6,12 @@
#ifndef __XFS_SCRUB_XFILE_H__
#define __XFS_SCRUB_XFILE_H__
struct xfile_page {
struct page *page;
void *fsdata;
loff_t pos;
};
struct xfile {
struct file *file;
};
@ -54,4 +60,8 @@ struct xfile_stat {
int xfile_stat(struct xfile *xf, struct xfile_stat *statbuf);
int xfile_get_page(struct xfile *xf, loff_t offset, unsigned int len,
struct xfile_page *xbuf);
int xfile_put_page(struct xfile *xf, struct xfile_page *xbuf);
#endif /* __XFS_SCRUB_XFILE_H__ */