[PATCH 55/64] afs: Handle len being extending over page end in write_begin/write_end
From: David Howells <dhowells@redhat.com>
Date: 2021-11-29 14:39:01
Also in:
ceph-devel, linux-cifs, linux-fsdevel, lkml
Subsystem:
afs filesystem, filesystems (vfs and infrastructure), the rest · Maintainers:
David Howells, Marc Dionne, Alexander Viro, Christian Brauner, Linus Torvalds
With transparent huge pages, in the future, write_begin() and write_end()
may be passed a length parameter that, in combination with the offset into
the page, exceeds the length of that page. This allows
grab_cache_page_write_begin() to better choose the size of THP to allocate.
Fix afs's functions to handle this by trimming the length as needed after
the page has been allocated.
[Removed the now-unnecessary index var; spotted by kernel test robot]
Fixes: e1b1240c1ff5 ("netfs: Add write_begin helper")
Reported-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Jeff Layton <jlayton@kernel.org>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Link: https://lore.kernel.org/r/162367681795.460125.11729955608839747375.stgit@warthog.procyon.org.uk/ (local) # v1
---
fs/afs/write.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/fs/afs/write.c b/fs/afs/write.c
index ca4909baf5e6..8e4e87d66855 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c@@ -25,7 +25,8 @@ int afs_set_page_dirty(struct page *page) } /* - * prepare to perform part of a write to a page + * Prepare to perform part of a write to a page. Note that len may extend + * beyond the end of the page. */ int afs_write_begin(struct file *file, struct address_space *mapping, loff_t pos, unsigned len, unsigned flags,
@@ -36,7 +37,6 @@ int afs_write_begin(struct file *file, struct address_space *mapping, unsigned long priv; unsigned f, from; unsigned t, to; - pgoff_t index; int ret; _enter("{%llx:%llu},%llx,%x",
@@ -51,8 +51,8 @@ int afs_write_begin(struct file *file, struct address_space *mapping, if (ret < 0) return ret; - index = folio_index(folio); - from = pos - index * PAGE_SIZE; + from = offset_in_folio(folio, pos); + len = min_t(size_t, len, folio_size(folio) - from); to = from + len; try_again:
@@ -103,7 +103,8 @@ int afs_write_begin(struct file *file, struct address_space *mapping, } /* - * finalise part of a write to a page + * Finalise part of a write to a page. Note that len may extend beyond the end + * of the page. */ int afs_write_end(struct file *file, struct address_space *mapping, loff_t pos, unsigned len, unsigned copied,