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Btrfs: Fix the unplug_io_fn to grab a consistent copy of page->mapping

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Signed-off-by: Chris Mason <chris.mason@oracle.com>
This commit is contained in:
Chris Mason 2008-04-22 13:26:47 -04:00
parent e1c4b7451e
commit bcbfce8abd
2 changed files with 22 additions and 7 deletions
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13
fs/btrfs/disk-io.c
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@ -936,14 +936,25 @@ void btrfs_unplug_io_fn(struct backing_dev_info *bdi, struct page *page)
struct inode *inode;
struct extent_map_tree *em_tree;
struct extent_map *em;
struct address_space *mapping;
u64 offset;
/* the generic O_DIRECT read code does this */
if (!page) {
__unplug_io_fn(bdi, page);
return;
}
inode = page->mapping->host;
/*
* page->mapping may change at any time. Get a consistent copy
* and use that for everything below
*/
smp_mb();
mapping = page->mapping;
if (!mapping)
return;
inode = mapping->host;
offset = page_offset(page);
em_tree = &BTRFS_I(inode)->extent_tree;