[PATCH RFC 07/20] fs: use must_set_pos()

[Christian Brauner <brauner@kernel.org>]

Make generic_file_llseek_size() use must_set_pos(). We'll use
must_set_pos() in another helper in a minutes. Remove __maybe_unused
from must_set_pos() now that it's used.

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 fs/read_write.c | 51 ++++++++++++++-------------------------------------
 1 file changed, 14 insertions(+), 37 deletions(-)

diff --git a/fs/read_write.c b/fs/read_write.c
index acee26989d95..ad93b72cc378 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -97,7 +97,7 @@ EXPORT_SYMBOL(vfs_setpos);
  * Return: 0 if f_pos doesn't need to be updated, 1 if f_pos has to be
  * updated, and negative error code on failure.
  */
-static __maybe_unused int must_set_pos(struct file *file, loff_t *offset, int whence, loff_t eof)
+static int must_set_pos(struct file *file, loff_t *offset, int whence, loff_t eof)
 {
 	switch (whence) {
 	case SEEK_END:
@@ -157,45 +157,22 @@ loff_t
 generic_file_llseek_size(struct file *file, loff_t offset, int whence,
 		loff_t maxsize, loff_t eof)
 {
-	switch (whence) {
-	case SEEK_END:
-		offset += eof;
-		break;
-	case SEEK_CUR:
-		/*
-		 * Here we special-case the lseek(fd, 0, SEEK_CUR)
-		 * position-querying operation.  Avoid rewriting the "same"
-		 * f_pos value back to the file because a concurrent read(),
-		 * write() or lseek() might have altered it
-		 */
-		if (offset == 0)
-			return file->f_pos;
-		/*
-		 * f_lock protects against read/modify/write race with other
-		 * SEEK_CURs. Note that parallel writes and reads behave
-		 * like SEEK_SET.
-		 */
-		spin_lock(&file->f_lock);
-		offset = vfs_setpos(file, file->f_pos + offset, maxsize);
-		spin_unlock(&file->f_lock);
+	int ret;
+
+	ret = must_set_pos(file, &offset, whence, eof);
+	if (ret < 0)
+		return ret;
+	if (ret == 0)
 		return offset;
-	case SEEK_DATA:
-		/*
-		 * In the generic case the entire file is data, so as long as
-		 * offset isn't at the end of the file then the offset is data.
-		 */
-		if ((unsigned long long)offset >= eof)
-			return -ENXIO;
-		break;
-	case SEEK_HOLE:
+
+	if (whence == SEEK_CUR) {
 		/*
-		 * There is a virtual hole at the end of the file, so as long as
-		 * offset isn't i_size or larger, return i_size.
+		 * f_lock protects against read/modify/write race with
+		 * other SEEK_CURs. Note that parallel writes and reads
+		 * behave like SEEK_SET.
 		 */
-		if ((unsigned long long)offset >= eof)
-			return -ENXIO;
-		offset = eof;
-		break;
+		guard(spinlock)(&file->f_lock);
+		return vfs_setpos(file, file->f_pos + offset, maxsize);
 	}
 
 	return vfs_setpos(file, offset, maxsize);

-- 
2.45.2