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Commit 7fc9e472 authored by Goldwyn Rodrigues's avatar Goldwyn Rodrigues Committed by Jens Axboe
Browse files

fs: Introduce filemap_range_has_page() 



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.

Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarGoldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent fdd2f5b7

include/linux/fs.h

+2 −0
Original line number Diff line number Diff line
@@ -2518,6 +2518,8 @@ 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 bool 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);

mm/filemap.c

+32 −0
Original line number Diff line number Diff line
@@ -376,6 +376,38 @@ 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 within which to check

 * @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.

 */

bool 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;

	bool ret;



	if (end_byte < start_byte)

		return false;



	if (mapping->nrpages == 0)

		return false;



	pagevec_init(&pvec, 0);

	if (!pagevec_lookup(&pvec, mapping, index, 1))

		return false;

	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)

{