[PATCH 02/10] fs: Introduce filemap_range_has_page()
From: Goldwyn Rodrigues <hidden>
Date: 2017-05-24 16:42:05
Also in:
linux-api, linux-btrfs, linux-ext4, linux-fsdevel, linux-xfs
Subsystem:
filesystems (vfs and infrastructure), memory management, page cache, the rest · Maintainers:
Alexander Viro, Christian Brauner, Andrew Morton, Matthew Wilcox, Linus Torvalds
From: Goldwyn Rodrigues <redacted> filemap_range_has_page() return true if the file's mapping has a page within the range mentioned. This function will be used to check if a write() call will cause a writeback of previous writes. Signed-off-by: Goldwyn Rodrigues <redacted> Reviewed-by: Christoph Hellwig <hch@lst.de> --- include/linux/fs.h | 2 ++ mm/filemap.c | 33 +++++++++++++++++++++++++++++++++ 2 files changed, 35 insertions(+)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index f53867140f43..dc0ab585cd56 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h@@ -2517,6 +2517,8 @@ extern int filemap_fdatawait(struct address_space *); extern void filemap_fdatawait_keep_errors(struct address_space *); extern int filemap_fdatawait_range(struct address_space *, loff_t lstart, loff_t lend); +extern int filemap_range_has_page(struct address_space *, loff_t lstart, + loff_t lend); extern int filemap_write_and_wait(struct address_space *mapping); extern int filemap_write_and_wait_range(struct address_space *mapping, loff_t lstart, loff_t lend);
diff --git a/mm/filemap.c b/mm/filemap.c
index 6f1be573a5e6..87aba7698584 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c@@ -376,6 +376,39 @@ int filemap_flush(struct address_space *mapping) } EXPORT_SYMBOL(filemap_flush); +/** + * filemap_range_has_page - check if a page exists in range. + * @mapping: address space structure to wait for + * @start_byte: offset in bytes where the range starts + * @end_byte: offset in bytes where the range ends (inclusive) + * + * Find at least one page in the range supplied, usually used to check if + * direct writing in this range will trigger a writeback. + */ +int filemap_range_has_page(struct address_space *mapping, + loff_t start_byte, loff_t end_byte) +{ + pgoff_t index = start_byte >> PAGE_SHIFT; + pgoff_t end = end_byte >> PAGE_SHIFT; + struct pagevec pvec; + int ret; + + if (end_byte < start_byte) + return 0; + + if (mapping->nrpages == 0) + return 0; + + pagevec_init(&pvec, 0); + ret = pagevec_lookup(&pvec, mapping, index, 1); + if (!ret) + return 0; + ret = (pvec.pages[0]->index <= end); + pagevec_release(&pvec); + return ret; +} +EXPORT_SYMBOL(filemap_range_has_page); + static int __filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte, loff_t end_byte) {
--
2.12.0