diff options
| -rw-r--r-- | fs/read_write.c | 49 |
1 files changed, 41 insertions, 8 deletions
diff --git a/fs/read_write.c b/fs/read_write.c index 1f5088dec566..5bbf587f5bc1 100644 --- a/fs/read_write.c +++ b/fs/read_write.c @@ -1811,10 +1811,7 @@ static int generic_remap_check_len(struct inode *inode_in, return (remap_flags & REMAP_FILE_DEDUP) ? -EBADE : -EINVAL; } -/* - * Read a page's worth of file data into the page cache. Return the page - * locked. - */ +/* Read a page's worth of file data into the page cache. */ static struct page *vfs_dedupe_get_page(struct inode *inode, loff_t offset) { struct page *page; @@ -1826,11 +1823,33 @@ static struct page *vfs_dedupe_get_page(struct inode *inode, loff_t offset) put_page(page); return ERR_PTR(-EIO); } - lock_page(page); return page; } /* + * Lock two pages, ensuring that we lock in offset order if the pages are from + * the same file. + */ +static void vfs_lock_two_pages(struct page *page1, struct page *page2) +{ + /* Always lock in order of increasing index. */ + if (page1->index > page2->index) + swap(page1, page2); + + lock_page(page1); + if (page1 != page2) + lock_page(page2); +} + +/* Unlock two pages, being careful not to unlock the same page twice. */ +static void vfs_unlock_two_pages(struct page *page1, struct page *page2) +{ + unlock_page(page1); + if (page1 != page2) + unlock_page(page2); +} + +/* * Compare extents of two files to see if they are the same. * Caller must have locked both inodes to prevent write races. */ @@ -1867,10 +1886,24 @@ static int vfs_dedupe_file_range_compare(struct inode *src, loff_t srcoff, dest_page = vfs_dedupe_get_page(dest, destoff); if (IS_ERR(dest_page)) { error = PTR_ERR(dest_page); - unlock_page(src_page); put_page(src_page); goto out_error; } + + vfs_lock_two_pages(src_page, dest_page); + + /* + * Now that we've locked both pages, make sure they're still + * mapped to the file data we're interested in. If not, + * someone is invalidating pages on us and we lose. + */ + if (!PageUptodate(src_page) || !PageUptodate(dest_page) || + src_page->mapping != src->i_mapping || + dest_page->mapping != dest->i_mapping) { + same = false; + goto unlock; + } + src_addr = kmap_atomic(src_page); dest_addr = kmap_atomic(dest_page); @@ -1882,8 +1915,8 @@ static int vfs_dedupe_file_range_compare(struct inode *src, loff_t srcoff, kunmap_atomic(dest_addr); kunmap_atomic(src_addr); - unlock_page(dest_page); - unlock_page(src_page); +unlock: + vfs_unlock_two_pages(src_page, dest_page); put_page(dest_page); put_page(src_page); |