[PATCH] xfs: fix sub-page uptodate handling

Christoph Hellwig
2019-12-04T17:30:21Z

bio complentions can race when a page spans more than one file system
block. Add a spinlock to synchronize marking the page uptodate.

Fixes: 9dc55f1389f9 ("iomap: add support for sub-pagesize buffered I/O without buffer heads")
Reported-by: Jan Stancek <jstancek@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
fs/iomap/buffered-io.c | 35 +++++++++++++++++++++++++----------
1 file changed, 25 insertions(+), 10 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 512856a88106..340c15400423 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -28,6 +28,7 @@
struct iomap_page {
atomic_t read_count;
atomic_t write_count;
+ spinlock_t uptodate_lock;
DECLARE_BITMAP(uptodate, PAGE_SIZE / 512);
};

@@ -51,6 +52,7 @@ iomap_page_create(struct inode *inode, struct page *page)
iop = kmalloc(sizeof(*iop), GFP_NOFS | __GFP_NOFAIL);
atomic_set(&iop->read_count, 0);
atomic_set(&iop->write_count, 0);
+ spin_lock_init(&iop->uptodate_lock);
bitmap_zero(iop->uptodate, PAGE_SIZE / SECTOR_SIZE);

/*
@@ -139,25 +141,38 @@ iomap_adjust_read_range(struct inode *inode, struct iomap_page *iop,
}

static void
-iomap_set_range_uptodate(struct page *page, unsigned off, unsigned len)
+iomap_iop_set_range_uptodate(struct page *page, unsigned off, unsigned len)
{
struct iomap_page *iop = to_iomap_page(page);
struct inode *inode = page->mapping->host;
unsigned first = off >> inode->i_blkbits;
unsigned last = (off + len - 1) >> inode->i_blkbits;
- unsigned int i;
bool uptodate = true;
+ unsigned long flags;
+ unsigned int i;

- if (iop) {
- for (i = 0; i < PAGE_SIZE / i_blocksize(inode); i++) {
- if (i >= first && i <= last)
- set_bit(i, iop->uptodate);
- else if (!test_bit(i, iop->uptodate))
- uptodate = false;
- }
+ spin_lock_irqsave(&iop->uptodate_lock, flags);
+ for (i = 0; i < PAGE_SIZE / i_blocksize(inode); i++) {
+ if (i >= first && i <= last)
+ set_bit(i, iop->uptodate);
+ else if (!test_bit(i, iop->uptodate))
+ uptodate = false;
}

- if (uptodate && !PageError(page))
+ if (uptodate)
+ SetPageUptodate(page);
+ spin_unlock_irqrestore(&iop->uptodate_lock, flags);
+}
+
+static void
+iomap_set_range_uptodate(struct page *page, unsigned off, unsigned len)
+{
+ if (PageError(page))
+ return;
+
+ if (page_has_private(page))
+ iomap_iop_set_range_uptodate(page, off, len);
+ else
SetPageUptodate(page);
}

--
2.20.1