From: David Howells <dhowells@redhat.com>
To: linux-cachefs@redhat.com, linux-afs@lists.infradead.org
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>,
Jeff Layton <jlayton@kernel.org>,
dhowells@redhat.com, Jeff Layton <jlayton@kernel.org>,
"Matthew Wilcox (Oracle)" <willy@infradead.org>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v2 1/3] afs: Handle len being extending over page end in write_begin/write_end
Date: Thu, 17 Jun 2021 09:24:02 +0100 [thread overview]
Message-ID: <162391824293.1173366.15452474691364794223.stgit@warthog.procyon.org.uk> (raw)
In-Reply-To: <162391823192.1173366.9740514875196345746.stgit@warthog.procyon.org.uk>
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: linux-afs@lists.infradead.org
Link: https://lore.kernel.org/r/162367681795.460125.11729955608839747375.stgit@warthog.procyon.org.uk/ # v1
---
fs/afs/write.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)
diff --git a/fs/afs/write.c b/fs/afs/write.c
index a523bb86915d..56e2cff2cb87 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 = page->index;
- from = pos - index * PAGE_SIZE;
+ from = offset_in_thp(page, pos);
+ len = min_t(size_t, len, thp_size(page) - 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,
@@ -111,7 +112,7 @@ int afs_write_end(struct file *file, struct address_space *mapping,
{
struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
unsigned long priv;
- unsigned int f, from = pos & (thp_size(page) - 1);
+ unsigned int f, from = offset_in_thp(page, pos);
unsigned int t, to = from + copied;
loff_t i_size, maybe_i_size;
next prev parent reply other threads:[~2021-06-17 8:24 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-17 8:23 [PATCH v2 0/3] netfs, afs: Fix netfs_write_begin and THP handling David Howells
2021-06-17 8:24 ` David Howells [this message]
2021-06-21 14:32 ` [PATCH v2 1/3] afs: Handle len being extending over page end in write_begin/write_end Matthew Wilcox
2021-06-17 8:24 ` [PATCH v2 2/3] afs: Fix afs_write_end() to handle short writes David Howells
2021-06-21 14:36 ` Matthew Wilcox
2021-06-17 8:24 ` [PATCH v2 3/3] netfs: fix test for whether we can skip read when writing beyond EOF David Howells
2021-06-21 14:50 ` Matthew Wilcox
2021-06-18 3:46 ` [PATCH v2 0/3] netfs, afs: Fix netfs_write_begin and THP handling Al Viro
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