diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 96c664af8d069f9f5d96d77efea7b293f2549fe6..a452b13620a228739fe60f296e85720643bf03e0 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -213,7 +213,7 @@ static int do_lo_send_aops(struct loop_device *lo, struct bio_vec *bvec,
struct address_space_operations *aops = mapping->a_ops;
pgoff_t index;
unsigned offset, bv_offs;
- int len, ret = 0;
+ int len, ret;
down(&mapping->host->i_sem);
index = pos >> PAGE_CACHE_SHIFT;
@@ -232,9 +232,15 @@ static int do_lo_send_aops(struct loop_device *lo, struct bio_vec *bvec,
page = grab_cache_page(mapping, index);
if (unlikely(!page))
goto fail;
- if (unlikely(aops->prepare_write(file, page, offset,
- offset + size)))
+ ret = aops->prepare_write(file, page, offset,
+ offset + size);
+ if (unlikely(ret)) {
+ if (ret == AOP_TRUNCATED_PAGE) {
+ page_cache_release(page);
+ continue;
+ }
goto unlock;
+ }
transfer_result = lo_do_transfer(lo, WRITE, page, offset,
bvec->bv_page, bv_offs, size, IV);
if (unlikely(transfer_result)) {
@@ -251,9 +257,15 @@ static int do_lo_send_aops(struct loop_device *lo, struct bio_vec *bvec,
kunmap_atomic(kaddr, KM_USER0);
}
flush_dcache_page(page);
- if (unlikely(aops->commit_write(file, page, offset,
- offset + size)))
+ ret = aops->commit_write(file, page, offset,
+ offset + size);
+ if (unlikely(ret)) {
+ if (ret == AOP_TRUNCATED_PAGE) {
+ page_cache_release(page);
+ continue;
+ }
goto unlock;
+ }
if (unlikely(transfer_result))
goto unlock;
bv_offs += size;
@@ -264,6 +276,7 @@ static int do_lo_send_aops(struct loop_device *lo, struct bio_vec *bvec,
unlock_page(page);
page_cache_release(page);
}
+ ret = 0;
out:
up(&mapping->host->i_sem);
return ret;
diff --git a/drivers/block/rd.c b/drivers/block/rd.c
index 68c60a5bcdabaf4f172854bbd1df959ecbe80689..ffd6abd6d5a045f40dd98a92486e1d21ea29e81c 100644
--- a/drivers/block/rd.c
+++ b/drivers/block/rd.c
@@ -154,7 +154,7 @@ static int ramdisk_commit_write(struct file *file, struct page *page,
/*
* ->writepage to the the blockdev's mapping has to redirty the page so that the
- * VM doesn't go and steal it. We return WRITEPAGE_ACTIVATE so that the VM
+ * VM doesn't go and steal it. We return AOP_WRITEPAGE_ACTIVATE so that the VM
* won't try to (pointlessly) write the page again for a while.
*
* Really, these pages should not be on the LRU at all.
@@ -165,7 +165,7 @@ static int ramdisk_writepage(struct page *page, struct writeback_control *wbc)
make_page_uptodate(page);
SetPageDirty(page);
if (wbc->for_reclaim)
- return WRITEPAGE_ACTIVATE;
+ return AOP_WRITEPAGE_ACTIVATE;
unlock_page(page);
return 0;
}
diff --git a/fs/mpage.c b/fs/mpage.c
index c5adcdddf3cc457dabb7af2197f69684a4b86020..f1d2d02bd4c81ebeb0ccde0c2d66d6c4a980d3d3 100644
--- a/fs/mpage.c
+++ b/fs/mpage.c
@@ -721,7 +721,7 @@ mpage_writepages(struct address_space *mapping,
&last_block_in_bio, &ret, wbc,
page->mapping->a_ops->writepage);
}
- if (unlikely(ret == WRITEPAGE_ACTIVATE))
+ if (unlikely(ret == AOP_WRITEPAGE_ACTIVATE))
unlock_page(page);
if (ret || (--(wbc->nr_to_write) <= 0))
done = 1;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index cc35b6ac778d6778f51a5112bc2569b9c1f563f4..ed9a41a71e8b57ff62ea245fbbe46e586d74c5ee 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -302,6 +302,37 @@ struct iattr {
*/
#include <linux/quota.h>
+/**
+ * enum positive_aop_returns - aop return codes with specific semantics
+ *
+ * @AOP_WRITEPAGE_ACTIVATE: Informs the caller that page writeback has
+ * completed, that the page is still locked, and
+ * should be considered active. The VM uses this hint
+ * to return the page to the active list -- it won't
+ * be a candidate for writeback again in the near
+ * future. Other callers must be careful to unlock
+ * the page if they get this return. Returned by
+ * writepage();
+ *
+ * @AOP_TRUNCATED_PAGE: The AOP method that was handed a locked page has
+ * unlocked it and the page might have been truncated.
+ * The caller should back up to acquiring a new page and
+ * trying again. The aop will be taking reasonable
+ * precautions not to livelock. If the caller held a page
+ * reference, it should drop it before retrying. Returned
+ * by readpage(), prepare_write(), and commit_write().
+ *
+ * address_space_operation functions return these large constants to indicate
+ * special semantics to the caller. These are much larger than the bytes in a
+ * page to allow for functions that return the number of bytes operated on in a
+ * given page.
+ */
+
+enum positive_aop_returns {
+ AOP_WRITEPAGE_ACTIVATE = 0x80000,
+ AOP_TRUNCATED_PAGE = 0x80001,
+};
+
/*
* oh the beauties of C type declarations.
*/
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index 343d883d69c5d56314b7b15280513376f1b6d1bd..64a36ba43b2f051cc74ad32329b59b8dfcbc336e 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -59,12 +59,6 @@ struct writeback_control {
unsigned for_reclaim:1; /* Invoked from the page allocator */
};
-/*
- * ->writepage() return values (make these much larger than a pagesize, in
- * case some fs is returning number-of-bytes-written from writepage)
- */
-#define WRITEPAGE_ACTIVATE 0x80000 /* IO was not started: activate page */
-
/*
* fs/fs-writeback.c
*/
diff --git a/mm/filemap.c b/mm/filemap.c
index 33a28bfde158a5c6e403fa11992cd2e897fe6868..6e1d08a2b8b9e1f8f690b91e2510f60070fecb55 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -831,8 +831,13 @@ void do_generic_mapping_read(struct address_space *mapping,
/* Start the actual read. The read will unlock the page. */
error = mapping->a_ops->readpage(filp, page);
- if (unlikely(error))
+ if (unlikely(error)) {
+ if (error == AOP_TRUNCATED_PAGE) {
+ page_cache_release(page);
+ goto find_page;
+ }
goto readpage_error;
+ }
if (!PageUptodate(page)) {
lock_page(page);
@@ -1152,26 +1157,24 @@ static int fastcall page_cache_read(struct file * file, unsigned long offset)
{
struct address_space *mapping = file->f_mapping;
struct page *page;
- int error;
+ int ret;
- page = page_cache_alloc_cold(mapping);
- if (!page)
- return -ENOMEM;
+ do {
+ page = page_cache_alloc_cold(mapping);
+ if (!page)
+ return -ENOMEM;
+
+ ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL);
+ if (ret == 0)
+ ret = mapping->a_ops->readpage(file, page);
+ else if (ret == -EEXIST)
+ ret = 0; /* losing race to add is OK */
- error = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL);
- if (!error) {
- error = mapping->a_ops->readpage(file, page);
page_cache_release(page);
- return error;
- }
- /*
- * We arrive here in the unlikely event that someone
- * raced with us and added our page to the cache first
- * or we are out of memory for radix-tree nodes.
- */
- page_cache_release(page);
- return error == -EEXIST ? 0 : error;
+ } while (ret == AOP_TRUNCATED_PAGE);
+
+ return ret;
}
#define MMAP_LOTSAMISS (100)
@@ -1331,10 +1334,14 @@ struct page *filemap_nopage(struct vm_area_struct *area,
goto success;
}
- if (!mapping->a_ops->readpage(file, page)) {
+ error = mapping->a_ops->readpage(file, page);
+ if (!error) {
wait_on_page_locked(page);
if (PageUptodate(page))
goto success;
+ } else if (error == AOP_TRUNCATED_PAGE) {
+ page_cache_release(page);
+ goto retry_find;
}
/*
@@ -1358,10 +1365,14 @@ struct page *filemap_nopage(struct vm_area_struct *area,
goto success;
}
ClearPageError(page);
- if (!mapping->a_ops->readpage(file, page)) {
+ error = mapping->a_ops->readpage(file, page);
+ if (!error) {
wait_on_page_locked(page);
if (PageUptodate(page))
goto success;
+ } else if (error == AOP_TRUNCATED_PAGE) {
+ page_cache_release(page);
+ goto retry_find;
}
/*
@@ -1444,10 +1455,14 @@ static struct page * filemap_getpage(struct file *file, unsigned long pgoff,
goto success;
}
- if (!mapping->a_ops->readpage(file, page)) {
+ error = mapping->a_ops->readpage(file, page);
+ if (!error) {
wait_on_page_locked(page);
if (PageUptodate(page))
goto success;
+ } else if (error == AOP_TRUNCATED_PAGE) {
+ page_cache_release(page);
+ goto retry_find;
}
/*
@@ -1470,10 +1485,14 @@ static struct page * filemap_getpage(struct file *file, unsigned long pgoff,
}
ClearPageError(page);
- if (!mapping->a_ops->readpage(file, page)) {
+ error = mapping->a_ops->readpage(file, page);
+ if (!error) {
wait_on_page_locked(page);
if (PageUptodate(page))
goto success;
+ } else if (error == AOP_TRUNCATED_PAGE) {
+ page_cache_release(page);
+ goto retry_find;
}
/*
@@ -1934,12 +1953,16 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
status = a_ops->prepare_write(file, page, offset, offset+bytes);
if (unlikely(status)) {
loff_t isize = i_size_read(inode);
+
+ if (status != AOP_TRUNCATED_PAGE)
+ unlock_page(page);
+ page_cache_release(page);
+ if (status == AOP_TRUNCATED_PAGE)
+ continue;
/*
* prepare_write() may have instantiated a few blocks
* outside i_size. Trim these off again.
*/
- unlock_page(page);
- page_cache_release(page);
if (pos + bytes > isize)
vmtruncate(inode, isize);
break;
@@ -1952,6 +1975,10 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
cur_iov, iov_base, bytes);
flush_dcache_page(page);
status = a_ops->commit_write(file, page, offset, offset+bytes);
+ if (status == AOP_TRUNCATED_PAGE) {
+ page_cache_release(page);
+ continue;
+ }
if (likely(copied > 0)) {
if (!status)
status = copied;
diff --git a/mm/readahead.c b/mm/readahead.c
index 72e7adbb87c7dd1e08cc1eb2851bdb96300d7e02..8d6eeaaa6296f9fb2372cff059138cbdd4b89723 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -158,7 +158,7 @@ static int read_pages(struct address_space *mapping, struct file *filp,
{
unsigned page_idx;
struct pagevec lru_pvec;
- int ret = 0;
+ int ret;
if (mapping->a_ops->readpages) {
ret = mapping->a_ops->readpages(filp, mapping, pages, nr_pages);
@@ -171,14 +171,17 @@ static int read_pages(struct address_space *mapping, struct file *filp,
list_del(&page->lru);
if (!add_to_page_cache(page, mapping,
page->index, GFP_KERNEL)) {
- mapping->a_ops->readpage(filp, page);
- if (!pagevec_add(&lru_pvec, page))
- __pagevec_lru_add(&lru_pvec);
- } else {
- page_cache_release(page);
+ ret = mapping->a_ops->readpage(filp, page);
+ if (ret != AOP_TRUNCATED_PAGE) {
+ if (!pagevec_add(&lru_pvec, page))
+ __pagevec_lru_add(&lru_pvec);
+ continue;
+ } /* else fall through to release */
}
+ page_cache_release(page);
}
pagevec_lru_add(&lru_pvec);
+ ret = 0;
out:
return ret;
}
diff --git a/mm/shmem.c b/mm/shmem.c
index dc25565a61e95c1aaacc8b4aa67b4c3862acea4a..d9fc277940da5473e472087c115f5be10608c190 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -855,7 +855,7 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
swap_free(swap);
redirty:
set_page_dirty(page);
- return WRITEPAGE_ACTIVATE; /* Return with the page locked */
+ return AOP_WRITEPAGE_ACTIVATE; /* Return with the page locked */
}
#ifdef CONFIG_NUMA
diff --git a/mm/vmscan.c b/mm/vmscan.c
index b0cd81c32de6ca0f601bb1be3c12764beb37a8af..795a050fe4714cb781dac80dcfc9d3e3c8f45275 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -367,7 +367,7 @@ static pageout_t pageout(struct page *page, struct address_space *mapping)
res = mapping->a_ops->writepage(page, &wbc);
if (res < 0)
handle_write_error(mapping, page, res);
- if (res == WRITEPAGE_ACTIVATE) {
+ if (res == AOP_WRITEPAGE_ACTIVATE) {
ClearPageReclaim(page);
return PAGE_ACTIVATE;
}