docs/core-api/mm: fix return value descriptions in mm/

Many kernel-doc comments in mm/ have the return value descriptions
either misformatted or omitted at all which makes kernel-doc script
unhappy:

$ make V=1 htmldocs
...
./mm/util.c:36: info: Scanning doc for kstrdup
./mm/util.c:41: warning: No description found for return value of 'kstrdup'
./mm/util.c:57: info: Scanning doc for kstrdup_const
./mm/util.c:66: warning: No description found for return value of 'kstrdup_const'
./mm/util.c:75: info: Scanning doc for kstrndup
./mm/util.c:83: warning: No description found for return value of 'kstrndup'
...

Fixing the formatting and adding the missing return value descriptions
eliminates ~100 such warnings.

Link: http://lkml.kernel.org/r/1549549644-4903-4-git-send-email-rppt@linux.ibm.com
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 62 insertions, 11 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index e59fdecdab74..ae0022f6106d 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -392,6 +392,8 @@ static int filemap_check_and_keep_errors(struct address_space *mapping)
  * opposed to a regular memory cleansing writeback.  The difference between
  * these two operations is that if a dirty page/buffer is encountered, it must
  * be waited upon, and not just skipped over.
+ *
+ * Return: %0 on success, negative error code otherwise.
  */
 int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
                                 loff_t end, int sync_mode)
@@ -438,6 +440,8 @@ EXPORT_SYMBOL(filemap_fdatawrite_range);
  *
  * This is a mostly non-blocking flush.  Not suitable for data-integrity
  * purposes - I/O may not be started against all dirty pages.
+ *
+ * Return: %0 on success, negative error code otherwise.
  */
 int filemap_flush(struct address_space *mapping)
 {
@@ -453,6 +457,9 @@ EXPORT_SYMBOL(filemap_flush);
  *
  * Find at least one page in the range supplied, usually used to check if
  * direct writing in this range will trigger a writeback.
+ *
+ * Return: %true if at least one page exists in the specified range,
+ * %false otherwise.
  */
 bool filemap_range_has_page(struct address_space *mapping,
                            loff_t start_byte, loff_t end_byte)
@@ -529,6 +536,8 @@ static void __filemap_fdatawait_range(struct address_space *mapping,
  * Since the error status of the address space is cleared by this function,
  * callers are responsible for checking the return value and handling and/or
  * reporting the error.
+ *
+ * Return: error status of the address space.
  */
 int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
                             loff_t end_byte)
@@ -551,6 +560,8 @@ EXPORT_SYMBOL(filemap_fdatawait_range);
  * Since the error status of the file is advanced by this function,
  * callers are responsible for checking the return value and handling and/or
  * reporting the error.
+ *
+ * Return: error status of the address space vs. the file->f_wb_err cursor.
  */
 int file_fdatawait_range(struct file *file, loff_t start_byte, loff_t end_byte)
 {
@@ -572,6 +583,8 @@ EXPORT_SYMBOL(file_fdatawait_range);
  * Use this function if callers don't handle errors themselves.  Expected
  * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
  * fsfreeze(8)
+ *
+ * Return: error status of the address space.
  */
 int filemap_fdatawait_keep_errors(struct address_space *mapping)
 {
@@ -623,6 +636,8 @@ EXPORT_SYMBOL(filemap_write_and_wait);
  *
  * Note that @lend is inclusive (describes the last byte to be written) so
  * that this function can be used to write to the very end-of-file (end = -1).
+ *
+ * Return: error status of the address space.
  */
 int filemap_write_and_wait_range(struct address_space *mapping,
                                  loff_t lstart, loff_t lend)
@@ -678,6 +693,8 @@ EXPORT_SYMBOL(__filemap_set_wb_err);
  * While we handle mapping->wb_err with atomic operations, the f_wb_err
  * value is protected by the f_lock since we must ensure that it reflects
  * the latest value swapped in for this file descriptor.
+ *
+ * Return: %0 on success, negative error code otherwise.
  */
 int file_check_and_advance_wb_err(struct file *file)
 {
@@ -720,6 +737,8 @@ EXPORT_SYMBOL(file_check_and_advance_wb_err);
  *
  * After writing out and waiting on the data, we check and advance the
  * f_wb_err cursor to the latest value, and return any errors detected there.
+ *
+ * Return: %0 on success, negative error code otherwise.
  */
 int file_write_and_wait_range(struct file *file, loff_t lstart, loff_t lend)
 {
@@ -753,6 +772,8 @@ EXPORT_SYMBOL(file_write_and_wait_range);
  * caller must do that.
  *
  * The remove + add is atomic.  This function cannot fail.
+ *
+ * Return: %0
  */
 int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
 {
@@ -867,6 +888,8 @@ error:
  *
  * This function is used to add a page to the pagecache. It must be locked.
  * This function does not add the page to the LRU.  The caller must do that.
+ *
+ * Return: %0 on success, negative error code otherwise.
  */
 int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
                 pgoff_t offset, gfp_t gfp_mask)
@@ -1463,7 +1486,7 @@ EXPORT_SYMBOL(page_cache_prev_miss);
  * If the slot holds a shadow entry of a previously evicted page, or a
  * swap entry from shmem/tmpfs, it is returned.
  *
- * Otherwise, %NULL is returned.
+ * Return: the found page or shadow entry, %NULL if nothing is found.
  */
 struct page *find_get_entry(struct address_space *mapping, pgoff_t offset)
 {
@@ -1521,9 +1544,9 @@ EXPORT_SYMBOL(find_get_entry);
  * If the slot holds a shadow entry of a previously evicted page, or a
  * swap entry from shmem/tmpfs, it is returned.
  *
- * Otherwise, %NULL is returned.
- *
  * find_lock_entry() may sleep.
+ *
+ * Return: the found page or shadow entry, %NULL if nothing is found.
  */
 struct page *find_lock_entry(struct address_space *mapping, pgoff_t offset)
 {
@@ -1563,12 +1586,14 @@ EXPORT_SYMBOL(find_lock_entry);
  * - FGP_CREAT: If page is not present then a new page is allocated using
  *   @gfp_mask and added to the page cache and the VM's LRU
  *   list. The page is returned locked and with an increased
- *   refcount. Otherwise, NULL is returned.
+ *   refcount.
  *
  * If FGP_LOCK or FGP_CREAT are specified then the function may sleep even
  * if the GFP flags specified for FGP_CREAT are atomic.
  *
  * If there is a page cache page, it is returned with an increased refcount.
+ *
+ * Return: the found page or %NULL otherwise.
  */
 struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset,
         int fgp_flags, gfp_t gfp_mask)
@@ -1656,8 +1681,7 @@ EXPORT_SYMBOL(pagecache_get_page);
  * Any shadow entries of evicted pages, or swap entries from
  * shmem/tmpfs, are included in the returned array.
  *
- * find_get_entries() returns the number of pages and shadow entries
- * which were found.
+ * Return: the number of pages and shadow entries which were found.
  */
 unsigned find_get_entries(struct address_space *mapping,
                           pgoff_t start, unsigned int nr_entries,
@@ -1727,8 +1751,8 @@ retry:
  * indexes.  There may be holes in the indices due to not-present pages.
  * We also update @start to index the next page for the traversal.
  *
- * find_get_pages_range() returns the number of pages which were found. If this
- * number is smaller than @nr_pages, the end of specified range has been
+ * Return: the number of pages which were found. If this number is
+ * smaller than @nr_pages, the end of specified range has been
  * reached.
  */
 unsigned find_get_pages_range(struct address_space *mapping, pgoff_t *start,
@@ -1801,7 +1825,7 @@ out:
  * find_get_pages_contig() works exactly like find_get_pages(), except
  * that the returned number of pages are guaranteed to be contiguous.
  *
- * find_get_pages_contig() returns the number of pages which were found.
+ * Return: the number of pages which were found.
  */
 unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
                                unsigned int nr_pages, struct page **pages)
@@ -1862,6 +1886,8 @@ EXPORT_SYMBOL(find_get_pages_contig);
  *
  * Like find_get_pages, except we only return pages which are tagged with
  * @tag.   We update @index to index the next page for the traversal.
+ *
+ * Return: the number of pages which were found.
  */
 unsigned find_get_pages_range_tag(struct address_space *mapping, pgoff_t *index,
                         pgoff_t end, xa_mark_t tag, unsigned int nr_pages,
@@ -1939,6 +1965,8 @@ EXPORT_SYMBOL(find_get_pages_range_tag);
  *
  * Like find_get_entries, except we only return entries which are tagged with
  * @tag.
+ *
+ * Return: the number of entries which were found.
  */
 unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start,
                         xa_mark_t tag, unsigned int nr_entries,
@@ -2024,6 +2052,10 @@ static void shrink_readahead_size_eio(struct file *filp,
  *
  * This is really ugly. But the goto's actually try to clarify some
  * of the logic when it comes to error handling etc.
+ *
+ * Return:
+ * * total number of bytes copied, including those the were already @written
+ * * negative error code if nothing was copied
  */
 static ssize_t generic_file_buffered_read(struct kiocb *iocb,
                 struct iov_iter *iter, ssize_t written)
@@ -2285,6 +2317,9 @@ out:
  *
  * This is the "read_iter()" routine for all filesystems
  * that can use the page cache directly.
+ * Return:
+ * * number of bytes copied, even for partial reads
+ * * negative error code if nothing was read
  */
 ssize_t
 generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
@@ -2352,6 +2387,8 @@ EXPORT_SYMBOL(generic_file_read_iter);
  *
  * This adds the requested page to the page cache if it isn't already there,
  * and schedules an I/O to read in its contents from disk.
+ *
+ * Return: %0 on success, negative error code otherwise.
  */
 static int page_cache_read(struct file *file, pgoff_t offset, gfp_t gfp_mask)
 {
@@ -2466,6 +2503,8 @@ static void do_async_mmap_readahead(struct vm_area_struct *vma,
  * has not been released.
  *
  * We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set.
+ *
+ * Return: bitwise-OR of %VM_FAULT_ codes.
  */
 vm_fault_t filemap_fault(struct vm_fault *vmf)
 {
@@ -2851,6 +2890,8 @@ out:
  * not set, try to fill the page and wait for it to become unlocked.
  *
  * If the page does not get brought uptodate, return -EIO.
+ *
+ * Return: up to date page on success, ERR_PTR() on failure.
  */
 struct page *read_cache_page(struct address_space *mapping,
                                 pgoff_t index,
@@ -2871,6 +2912,8 @@ EXPORT_SYMBOL(read_cache_page);
  * any new page allocations done using the specified allocation flags.
  *
  * If the page does not get brought uptodate, return -EIO.
+ *
+ * Return: up to date page on success, ERR_PTR() on failure.
  */
 struct page *read_cache_page_gfp(struct address_space *mapping,
                                 pgoff_t index,
@@ -3254,6 +3297,10 @@ EXPORT_SYMBOL(generic_perform_write);
  * This function does *not* take care of syncing data in case of O_SYNC write.
  * A caller has to handle it. This is mainly due to the fact that we want to
  * avoid syncing under i_mutex.
+ *
+ * Return:
+ * * number of bytes written, even for truncated writes
+ * * negative error code if no data has been written at all
  */
 ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 {
@@ -3338,6 +3385,10 @@ EXPORT_SYMBOL(__generic_file_write_iter);
  * This is a wrapper around __generic_file_write_iter() to be used by most
  * filesystems. It takes care of syncing the file in case of O_SYNC file
  * and acquires i_mutex as needed.
+ * Return:
+ * * negative error code if no data has been written at all of
+ *   vfs_fsync_range() failed for a synchronous write
+ * * number of bytes written, even for truncated writes
  */
 ssize_t generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 {
@@ -3364,8 +3415,7 @@ EXPORT_SYMBOL(generic_file_write_iter);
  * @gfp_mask: memory allocation flags (and I/O mode)
  *
  * The address_space is to try to release any data against the page
- * (presumably at page->private).  If the release was successful, return '1'.
- * Otherwise return zero.
+ * (presumably at page->private).
  *
  * This may also be called if PG_fscache is set on a page, indicating that the
  * page is known to the local caching routines.
@@ -3373,6 +3423,7 @@ EXPORT_SYMBOL(generic_file_write_iter);
  * The @gfp_mask argument specifies whether I/O may be performed to release
  * this page (__GFP_IO), and whether the call may block (__GFP_RECLAIM & __GFP_FS).
  *
+ * Return: %1 if the release was successful, otherwise return zero.
  */
 int try_to_release_page(struct page *page, gfp_t gfp_mask)
 {