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xfs: teach xfile to pass back direct-map pages to caller
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>
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c390c64503
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3 changed files with 120 additions and 0 deletions
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@ -821,6 +821,8 @@ DEFINE_EVENT(xfile_class, name, \
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DEFINE_XFILE_EVENT(xfile_pread);
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DEFINE_XFILE_EVENT(xfile_pwrite);
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DEFINE_XFILE_EVENT(xfile_seek_data);
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DEFINE_XFILE_EVENT(xfile_get_page);
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DEFINE_XFILE_EVENT(xfile_put_page);
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TRACE_EVENT(xfarray_create,
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TP_PROTO(struct xfarray *xfa, unsigned long long required_capacity),
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@ -310,3 +310,111 @@ xfile_stat(
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statbuf->bytes = ks.blocks << SECTOR_SHIFT;
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return 0;
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}
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/*
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* Grab the (locked) page for a memory object. The object cannot span a page
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* boundary. Returns 0 (and a locked page) if successful, -ENOTBLK if we
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* cannot grab the page, or the usual negative errno.
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*/
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int
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xfile_get_page(
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struct xfile *xf,
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loff_t pos,
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unsigned int len,
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struct xfile_page *xfpage)
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{
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struct inode *inode = file_inode(xf->file);
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struct address_space *mapping = inode->i_mapping;
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const struct address_space_operations *aops = mapping->a_ops;
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struct page *page = NULL;
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void *fsdata = NULL;
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loff_t key = round_down(pos, PAGE_SIZE);
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unsigned int pflags;
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int error;
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if (inode->i_sb->s_maxbytes - pos < len)
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return -ENOMEM;
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if (len > PAGE_SIZE - offset_in_page(pos))
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return -ENOTBLK;
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trace_xfile_get_page(xf, pos, len);
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pflags = memalloc_nofs_save();
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/*
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* We call write_begin directly here to avoid all the freezer
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* protection lock-taking that happens in the normal path. shmem
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* doesn't support fs freeze, but lockdep doesn't know that and will
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* trip over that.
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*/
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error = aops->write_begin(NULL, mapping, key, PAGE_SIZE, &page,
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&fsdata);
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if (error)
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goto out_pflags;
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/* We got the page, so make sure we push out EOF. */
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if (i_size_read(inode) < pos + len)
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i_size_write(inode, pos + len);
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/*
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* If the page isn't up to date, fill it with zeroes before we hand it
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* to the caller and make sure the backing store will hold on to them.
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*/
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if (!PageUptodate(page)) {
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void *kaddr;
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kaddr = kmap_local_page(page);
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memset(kaddr, 0, PAGE_SIZE);
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kunmap_local(kaddr);
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SetPageUptodate(page);
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}
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/*
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* Mark each page dirty so that the contents are written to some
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* backing store when we drop this buffer, and take an extra reference
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* to prevent the xfile page from being swapped or removed from the
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* page cache by reclaim if the caller unlocks the page.
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*/
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set_page_dirty(page);
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get_page(page);
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xfpage->page = page;
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xfpage->fsdata = fsdata;
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xfpage->pos = key;
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out_pflags:
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memalloc_nofs_restore(pflags);
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return error;
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}
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/*
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* Release the (locked) page for a memory object. Returns 0 or a negative
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* errno.
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*/
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int
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xfile_put_page(
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struct xfile *xf,
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struct xfile_page *xfpage)
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{
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struct inode *inode = file_inode(xf->file);
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struct address_space *mapping = inode->i_mapping;
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const struct address_space_operations *aops = mapping->a_ops;
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unsigned int pflags;
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int ret;
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trace_xfile_put_page(xf, xfpage->pos, PAGE_SIZE);
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/* Give back the reference that we took in xfile_get_page. */
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put_page(xfpage->page);
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pflags = memalloc_nofs_save();
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ret = aops->write_end(NULL, mapping, xfpage->pos, PAGE_SIZE, PAGE_SIZE,
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xfpage->page, xfpage->fsdata);
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memalloc_nofs_restore(pflags);
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memset(xfpage, 0, sizeof(struct xfile_page));
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if (ret < 0)
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return ret;
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if (ret != PAGE_SIZE)
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return -EIO;
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return 0;
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}
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@ -6,6 +6,12 @@
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#ifndef __XFS_SCRUB_XFILE_H__
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#define __XFS_SCRUB_XFILE_H__
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struct xfile_page {
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struct page *page;
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void *fsdata;
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loff_t pos;
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};
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struct xfile {
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struct file *file;
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};
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@ -54,4 +60,8 @@ struct xfile_stat {
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int xfile_stat(struct xfile *xf, struct xfile_stat *statbuf);
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int xfile_get_page(struct xfile *xf, loff_t offset, unsigned int len,
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struct xfile_page *xbuf);
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int xfile_put_page(struct xfile *xf, struct xfile_page *xbuf);
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#endif /* __XFS_SCRUB_XFILE_H__ */
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