iomap: fix iomap_read_end() for already uptodate folios

iomap: fix iomap_read_end() for already uptodate folios

There are some cases where when iomap_read_end() is called, the folio
may already have been marked uptodate. For example, if the iomap block
needed zeroing, then the folio may have been marked uptodate after the
zeroing.

iomap_read_end() should unlock the folio instead of calling
folio_end_read(), which is how these cases were handled prior to commit
f8eaf79406fe ("iomap: simplify ->read_folio_range() error handling for
reads"). Calling folio_end_read() on an uptodate folio leads to buggy
behavior where marking an already uptodate folio as uptodate will XOR it
to be marked nonuptodate.

Fixes: f8eaf79406fe ("iomap: simplify ->read_folio_range() error handling for reads")
Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Link: https://patch.msgid.link/20251118211111.1027272-2-joannelkoong@gmail.com
Tested-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reported-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>