shmem_getpage return page locked
In the new aops, write_begin is supposed to return the page locked: though
I've seen no ill effects, that's been overlooked in the case of
shmem_write_begin, and should be fixed. Then shmem_write_end must unlock the
page: do so _after_ updating i_size, as we found to be important in other
filesystems (though since shmem pages don't go the usual writeback route, they
never suffered from that corruption).
For shmem_write_begin to return the page locked, we need shmem_getpage to
return the page locked in SGP_WRITE case as well as SGP_CACHE case: let's
simplify the interface and return it locked even when SGP_READ.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/shmem.c b/mm/shmem.c
index 20cefe1..43d0719 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -729,6 +729,8 @@
(void) shmem_getpage(inode,
attr->ia_size>>PAGE_CACHE_SHIFT,
&page, SGP_READ, NULL);
+ if (page)
+ unlock_page(page);
}
/*
* Reset SHMEM_PAGEIN flag so that shmem_truncate can
@@ -1286,12 +1288,7 @@
SetPageUptodate(filepage);
}
done:
- if (*pagep != filepage) {
- *pagep = filepage;
- if (sgp != SGP_CACHE)
- unlock_page(filepage);
-
- }
+ *pagep = filepage;
return 0;
failed:
@@ -1469,12 +1466,13 @@
{
struct inode *inode = mapping->host;
+ if (pos + copied > inode->i_size)
+ i_size_write(inode, pos + copied);
+
+ unlock_page(page);
set_page_dirty(page);
page_cache_release(page);
- if (pos+copied > inode->i_size)
- i_size_write(inode, pos+copied);
-
return copied;
}
@@ -1529,6 +1527,7 @@
if (err)
break;
+ unlock_page(page);
left = bytes;
if (PageHighMem(page)) {
volatile unsigned char dummy;
@@ -1610,6 +1609,8 @@
desc->error = 0;
break;
}
+ if (page)
+ unlock_page(page);
/*
* We must evaluate after, since reads (unlike writes)
@@ -1899,6 +1900,7 @@
iput(inode);
return error;
}
+ unlock_page(page);
inode->i_op = &shmem_symlink_inode_operations;
kaddr = kmap_atomic(page, KM_USER0);
memcpy(kaddr, symname, len);
@@ -1926,6 +1928,8 @@
struct page *page = NULL;
int res = shmem_getpage(dentry->d_inode, 0, &page, SGP_READ, NULL);
nd_set_link(nd, res ? ERR_PTR(res) : kmap(page));
+ if (page)
+ unlock_page(page);
return page;
}