[PATCH] CIFS: Fix readpages retrying on reconnects

[Pavel Shilovsky]

From: Pavel Shilovsky <pshilovsky-***@public.gmane.org>

If we got a reconnect error from async readv we re-add pages back
to page_list and continue loop. That is wrong because these pages
have been already added to the pagecache but page_list has pages that
have not been added to the pagecache yet. This ends up with a general
protection fault in put_pages after readpages. Fix it by not retrying
the read of these pages and falling back to readpage instead.

Signed-off-by: Pavel Shilovsky <pshilovsky-***@public.gmane.org>
---
fs/cifs/file.c | 8 +-------
1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 7c018a1..5f29354 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -3568,15 +3568,9 @@ static int cifs_readpages(struct file *file, struct address_space *mapping,
lru_cache_add_file(page);
unlock_page(page);
page_cache_release(page);
- if (rc == -EAGAIN)
- list_add_tail(&page->lru, &tmplist);
}
+ /* Fallback to the readpage in error/reconnect cases */
kref_put(&rdata->refcount, cifs_readdata_release);
- if (rc == -EAGAIN) {
- /* Re-add pages to the page_list and retry */
- list_splice(&tmplist, page_list);
- continue;
- }
break;
}

[Steve French]

Merged into cifs-2.6.git for-next (and for-linus)

I would like to get this and also
http://git.samba.org/?p=sfrench/cifs-2.6.git;a=commit;h=19e81573fca7b87ced7701e01ba164b968d929bd
upstream ASAP but timing is getting tight, will need to wait at least
a day for the normal linux-next build processes to complete and any
additional test results.

Post by Pavel Shilovsky
If we got a reconnect error from async readv we re-add pages back
to page_list and continue loop. That is wrong because these pages
have been already added to the pagecache but page_list has pages that
have not been added to the pagecache yet. This ends up with a general
protection fault in put_pages after readpages. Fix it by not retrying
the read of these pages and falling back to readpage instead.
---
fs/cifs/file.c | 8 +-------
1 file changed, 1 insertion(+), 7 deletions(-)
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 7c018a1..5f29354 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -3568,15 +3568,9 @@ static int cifs_readpages(struct file *file, struct address_space *mapping,
lru_cache_add_file(page);
unlock_page(page);
page_cache_release(page);
- if (rc == -EAGAIN)
- list_add_tail(&page->lru, &tmplist);
}
+ /* Fallback to the readpage in error/reconnect cases */
kref_put(&rdata->refcount, cifs_readdata_release);
- if (rc == -EAGAIN) {
- /* Re-add pages to the page_list and retry */
- list_splice(&tmplist, page_list);
- continue;
- }
break;
}
--
1.7.10.4
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