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Subject[PATCH 09/13] afs: Wait on PG_fscache before modifying/releasing a page
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PG_fscache is going to be used to indicate that a page is being written to
the cache, and that the page should not be modified or released until it's
finished.

Make afs_invalidatepage() and afs_releasepage() wait for it.

Signed-off-by: David Howells <dhowells@redhat.com>
---

fs/afs/file.c | 7 +++++++
fs/afs/write.c | 9 +++++++++
2 files changed, 16 insertions(+)

diff --git a/fs/afs/file.c b/fs/afs/file.c
index 8baafe655433..2f9a7369b77b 100644
--- a/fs/afs/file.c
+++ b/fs/afs/file.c
@@ -580,6 +580,13 @@ static int afs_releasepage(struct page *page, gfp_t gfp_flags)

/* deny if page is being written to the cache and the caller hasn't
* elected to wait */
+#ifdef CONFIG_AFS_FSCACHE
+ if (PageFsCache(page)) {
+ if (!(gfp_flags & __GFP_DIRECT_RECLAIM) || !(gfp_flags & __GFP_FS))
+ return false;
+ }
+#endif
+
if (PagePrivate(page)) {
priv = page_private(page);
trace_afs_page_dirty(vnode, tracepoint_string("rel"),
diff --git a/fs/afs/write.c b/fs/afs/write.c
index d9de0dc877ca..73e2f4c93512 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -125,6 +125,10 @@ int afs_write_begin(struct file *file, struct address_space *mapping,
SetPageUptodate(page);
}

+#ifdef CONFIG_AFS_FSCACHE
+ wait_on_page_fscache(page);
+#endif
+
/* page won't leak in error case: it eventually gets cleaned off LRU */
*pagep = page;

@@ -849,6 +853,11 @@ vm_fault_t afs_page_mkwrite(struct vm_fault *vmf)
/* Wait for the page to be written to the cache before we allow it to
* be modified. We then assume the entire page will need writing back.
*/
+#ifdef CONFIG_AFS_FSCACHE
+ if (PageFsCache(vmf->page) &&
+ wait_on_page_bit_killable(vmf->page, PG_fscache) < 0)
+ return VM_FAULT_RETRY;
+#endif

if (PageWriteback(vmf->page) &&
wait_on_page_bit_killable(vmf->page, PG_writeback) < 0)

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