It isn't necessary to zero page in nobh_writepage() since mpage_writepage()
takes care of that. We just have to use block_write_full_page() instead
of __block_write_full_page() to properly zero the page in case we have
to fallback to ordinary writepage.
Since __block_write_full_page is then only used from
block_write_full_page_endio() join them.
Signed-off-by: Jan Kara <jack@xxxxxxx>
---
fs/buffer.c | 426 +++++++++++++++++++++++++++--------------------------------
1 files changed, 196 insertions(+), 230 deletions(-)
diff --git a/fs/buffer.c b/fs/buffer.c
index 67b260a..0eaa961 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1589,207 +1589,6 @@ void unmap_underlying_metadata(struct block_device *bdev, sector_t block)
EXPORT_SYMBOL(unmap_underlying_metadata);
/*
- * NOTE! All mapped/uptodate combinations are valid:
- *
- * Mapped Uptodate Meaning
- *
- * No No "unknown" - must do get_block()
- * No Yes "hole" - zero-filled
- * Yes No "allocated" - allocated on disk, not read in
- * Yes Yes "valid" - allocated and up-to-date in memory.
- *
- * "Dirty" is valid only with the last case (mapped+uptodate).
- */
-
-/*
- * While block_write_full_page is writing back the dirty buffers under
- * the page lock, whoever dirtied the buffers may decide to clean them
- * again at any time. We handle that by only looking at the buffer
- * state inside lock_buffer().
- *
- * If block_write_full_page() is called for regular writeback
- * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
- * locked buffer. This only can happen if someone has written the buffer
- * directly, with submit_bh(). At the address_space level PageWriteback
- * prevents this contention from occurring.
- *
- * If block_write_full_page() is called with wbc->sync_mode ==
- * WB_SYNC_ALL, the writes are posted using WRITE_SYNC_PLUG; this
- * causes the writes to be flagged as synchronous writes, but the
- * block device queue will NOT be unplugged, since usually many pages
- * will be pushed to the out before the higher-level caller actually
- * waits for the writes to be completed. The various wait functions,
- * such as wait_on_writeback_range() will ultimately call sync_page()
- * which will ultimately call blk_run_backing_dev(), which will end up
- * unplugging the device queue.
- */
-static int __block_write_full_page(struct inode *inode, struct page *page,
- get_block_t *get_block, struct writeback_control *wbc,
- bh_end_io_t *handler)
-{
- int err;
- sector_t block;
- sector_t last_block;
- struct buffer_head *bh, *head;
- const unsigned blocksize = 1 << inode->i_blkbits;
- int nr_underway = 0;
- int write_op = (wbc->sync_mode == WB_SYNC_ALL ?
- WRITE_SYNC_PLUG : WRITE);
-
- BUG_ON(!PageLocked(page));
-
- last_block = (i_size_read(inode) - 1) >> inode->i_blkbits;
-
- if (!page_has_buffers(page)) {
- create_empty_buffers(page, blocksize,
- (1 << BH_Dirty)|(1 << BH_Uptodate));
- }
-
- /*
- * Be very careful. We have no exclusion from __set_page_dirty_buffers
- * here, and the (potentially unmapped) buffers may become dirty at
- * any time. If a buffer becomes dirty here after we've inspected it
- * then we just miss that fact, and the page stays dirty.
- *
- * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
- * handle that here by just cleaning them.
- */
-
- block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
- head = page_buffers(page);
- bh = head;
-
- /*
- * Get all the dirty buffers mapped to disk addresses and
- * handle any aliases from the underlying blockdev's mapping.
- */
- do {
- if (block > last_block) {
- /*
- * mapped buffers outside i_size will occur, because
- * this page can be outside i_size when there is a
- * truncate in progress.
- */
- /*
- * The buffer was zeroed by block_write_full_page()
- */
- clear_buffer_dirty(bh);
- set_buffer_uptodate(bh);
- } else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
- buffer_dirty(bh)) {
- WARN_ON(bh->b_size != blocksize);
- err = get_block(inode, block, bh, 1);
- if (err)
- goto recover;
- clear_buffer_delay(bh);
- if (buffer_new(bh)) {
- /* blockdev mappings never come here */
- clear_buffer_new(bh);
- unmap_underlying_metadata(bh->b_bdev,
- bh->b_blocknr);
- }
- }
- bh = bh->b_this_page;
- block++;
- } while (bh != head);
-
- do {
- if (!buffer_mapped(bh))
- continue;
- /*
- * If it's a fully non-blocking write attempt and we cannot
- * lock the buffer then redirty the page. Note that this can
- * potentially cause a busy-wait loop from pdflush and kswapd
- * activity, but those code paths have their own higher-level
- * throttling.
- */
- if (wbc->sync_mode != WB_SYNC_NONE || !wbc->nonblocking) {
- lock_buffer(bh);
- } else if (!trylock_buffer(bh)) {
- redirty_page_for_writepage(wbc, page);
- continue;
- }
- if (test_clear_buffer_dirty(bh)) {
- mark_buffer_async_write_endio(bh, handler);
- } else {
- unlock_buffer(bh);
- }
- } while ((bh = bh->b_this_page) != head);
-
- /*
- * The page and its buffers are protected by PageWriteback(), so we can
- * drop the bh refcounts early.
- */
- BUG_ON(PageWriteback(page));
- set_page_writeback(page);
-
- do {
- struct buffer_head *next = bh->b_this_page;
- if (buffer_async_write(bh)) {
- submit_bh(write_op, bh);
- nr_underway++;
- }
- bh = next;
- } while (bh != head);
- unlock_page(page);
-
- err = 0;
-done:
- if (nr_underway == 0) {
- /*
- * The page was marked dirty, but the buffers were
- * clean. Someone wrote them back by hand with
- * ll_rw_block/submit_bh. A rare case.
- */
- end_page_writeback(page);
-
- /*
- * The page and buffer_heads can be released at any time from
- * here on.
- */
- }
- return err;
-
-recover:
- /*
- * ENOSPC, or some other error. We may already have added some
- * blocks to the file, so we need to write these out to avoid
- * exposing stale data.
- * The page is currently locked and not marked for writeback
- */
- bh = head;
- /* Recovery: lock and submit the mapped buffers */
- do {
- if (buffer_mapped(bh) && buffer_dirty(bh) &&
- !buffer_delay(bh)) {
- lock_buffer(bh);
- mark_buffer_async_write_endio(bh, handler);
- } else {
- /*
- * The buffer may have been set dirty during
- * attachment to a dirty page.
- */
- clear_buffer_dirty(bh);
- }
- } while ((bh = bh->b_this_page) != head);
- SetPageError(page);
- BUG_ON(PageWriteback(page));
- mapping_set_error(page->mapping, err);
- set_page_writeback(page);
- do {
- struct buffer_head *next = bh->b_this_page;
- if (buffer_async_write(bh)) {
- clear_buffer_dirty(bh);
- submit_bh(write_op, bh);
- nr_underway++;
- }
- bh = next;
- } while (bh != head);
- unlock_page(page);
- goto done;
-}
-
-/*
* If a page has any new buffers, zero them out here, and mark them uptodate
* and dirty so they'll be written out (in order to prevent uninitialised
* block data from leaking). And clear the new bit.
@@ -2653,36 +2452,11 @@ EXPORT_SYMBOL(nobh_write_end);
int nobh_writepage(struct page *page, get_block_t *get_block,
struct writeback_control *wbc)
{
- struct inode * const inode = page->mapping->host;
- loff_t i_size = i_size_read(inode);
- const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
- unsigned offset;
int ret;
- /* Is the page fully inside i_size? */
- if (page->index < end_index)
- goto out;
-
- /* Is the page fully outside i_size? (truncate in progress) */
- offset = i_size & (PAGE_CACHE_SIZE-1);
- if (page->index >= end_index+1 || !offset) {
- unlock_page(page);
- return 0;
- }
-
- /*
- * The page straddles i_size. It must be zeroed out on each and every
- * writepage invocation because it may be mmapped. "A file is mapped
- * in multiples of the page size. For a file that is not a multiple of
- * the page size, the remaining memory is zeroed when mapped, and
- * writes to that region are not written out to the file."
- */
- zero_user_segment(page, offset, PAGE_CACHE_SIZE);
-out:
ret = mpage_writepage(page, get_block, wbc);
if (ret == -EAGAIN)
- ret = __block_write_full_page(inode, page, get_block, wbc,
- end_buffer_async_write);
+ ret = block_write_full_page(page, get_block, wbc);
return ret;
}
EXPORT_SYMBOL(nobh_writepage);
@@ -2841,21 +2615,64 @@ out:
}
/*
+ * NOTE! All mapped/uptodate combinations are valid:
+ *
+ * Mapped Uptodate Meaning
+ *
+ * No No "unknown" - must do get_block()
+ * No Yes "hole" - zero-filled
+ * Yes No "allocated" - allocated on disk, not read in
+ * Yes Yes "valid" - allocated and up-to-date in memory.
+ *
+ * "Dirty" is valid only with the last case (mapped+uptodate).
+ */
+
+/*
* The generic ->writepage function for buffer-backed address_spaces
* this form passes in the end_io handler used to finish the IO.
+ *
+ * While block_write_full_page is writing back the dirty buffers under
+ * the page lock, whoever dirtied the buffers may decide to clean them
+ * again at any time. We handle that by only looking at the buffer
+ * state inside lock_buffer().
+ *
+ * If block_write_full_page() is called for regular writeback
+ * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
+ * locked buffer. This only can happen if someone has written the buffer
+ * directly, with submit_bh(). At the address_space level PageWriteback
+ * prevents this contention from occurring.
+ *
+ * If block_write_full_page() is called with wbc->sync_mode ==
+ * WB_SYNC_ALL, the writes are posted using WRITE_SYNC_PLUG; this
+ * causes the writes to be flagged as synchronous writes, but the
+ * block device queue will NOT be unplugged, since usually many pages
+ * will be pushed to the out before the higher-level caller actually
+ * waits for the writes to be completed. The various wait functions,
+ * such as wait_on_writeback_range() will ultimately call sync_page()
+ * which will ultimately call blk_run_backing_dev(), which will end up
+ * unplugging the device queue.
*/
int block_write_full_page_endio(struct page *page, get_block_t *get_block,
struct writeback_control *wbc, bh_end_io_t *handler)
{
+ int err;
struct inode * const inode = page->mapping->host;
loff_t i_size = i_size_read(inode);
const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
unsigned offset;
+ sector_t block;
+ sector_t last_block;
+ struct buffer_head *bh, *head;
+ const unsigned blocksize = 1 << inode->i_blkbits;
+ int nr_underway = 0;
+ int write_op = (wbc->sync_mode == WB_SYNC_ALL ?
+ WRITE_SYNC_PLUG : WRITE);
+
+ BUG_ON(!PageLocked(page));
/* Is the page fully inside i_size? */
if (page->index < end_index)
- return __block_write_full_page(inode, page, get_block, wbc,
- handler);
+ goto write_page;
/* Is the page fully outside i_size? (truncate in progress) */
offset = i_size & (PAGE_CACHE_SIZE-1);
@@ -2872,7 +2689,156 @@ int block_write_full_page_endio(struct page *page, get_block_t *get_block,
* writes to that region are not written out to the file."
*/
zero_user_segment(page, offset, PAGE_CACHE_SIZE);
- return __block_write_full_page(inode, page, get_block, wbc, handler);
+write_page:
+ last_block = i_size >> inode->i_blkbits;
+
+ if (!page_has_buffers(page)) {
+ create_empty_buffers(page, blocksize,
+ (1 << BH_Dirty)|(1 << BH_Uptodate));
+ }
+
+ /*
+ * Be very careful. We have no exclusion from __set_page_dirty_buffers
+ * here, and the (potentially unmapped) buffers may become dirty at
+ * any time. If a buffer becomes dirty here after we've inspected it
+ * then we just miss that fact, and the page stays dirty.
+ *
+ * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
+ * handle that here by just cleaning them.
+ */
+
+ block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
+ head = page_buffers(page);
+ bh = head;
+
+ /*
+ * Get all the dirty buffers mapped to disk addresses and
+ * handle any aliases from the underlying blockdev's mapping.
+ */
+ do {
+ if (block > last_block) {
+ /*
+ * mapped buffers outside i_size will occur, because
+ * this page can be outside i_size when there is a
+ * truncate in progress.
+ */
+ /*
+ * The buffer was zeroed by block_write_full_page()
+ */
+ clear_buffer_dirty(bh);
+ set_buffer_uptodate(bh);
+ } else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
+ buffer_dirty(bh)) {
+ WARN_ON(bh->b_size != blocksize);
+ err = get_block(inode, block, bh, 1);
+ if (err)
+ goto recover;
+ clear_buffer_delay(bh);
+ if (buffer_new(bh)) {
+ /* blockdev mappings never come here */
+ clear_buffer_new(bh);
+ unmap_underlying_metadata(bh->b_bdev,
+ bh->b_blocknr);
+ }
+ }
+ bh = bh->b_this_page;
+ block++;
+ } while (bh != head);
+
+ do {
+ if (!buffer_mapped(bh))
+ continue;
+ /*
+ * If it's a fully non-blocking write attempt and we cannot
+ * lock the buffer then redirty the page. Note that this can
+ * potentially cause a busy-wait loop from pdflush and kswapd
+ * activity, but those code paths have their own higher-level
+ * throttling.
+ */
+ if (wbc->sync_mode != WB_SYNC_NONE || !wbc->nonblocking) {
+ lock_buffer(bh);
+ } else if (!trylock_buffer(bh)) {
+ redirty_page_for_writepage(wbc, page);
+ continue;
+ }
+ if (test_clear_buffer_dirty(bh)) {
+ mark_buffer_async_write_endio(bh, handler);
+ } else {
+ unlock_buffer(bh);
+ }
+ } while ((bh = bh->b_this_page) != head);
+
+ /*
+ * The page and its buffers are protected by PageWriteback(), so we can
+ * drop the bh refcounts early.
+ */
+ BUG_ON(PageWriteback(page));
+ set_page_writeback(page);
+
+ do {
+ struct buffer_head *next = bh->b_this_page;
+ if (buffer_async_write(bh)) {
+ submit_bh(write_op, bh);
+ nr_underway++;
+ }
+ bh = next;
+ } while (bh != head);
+ unlock_page(page);
+
+ err = 0;
+done:
+ if (nr_underway == 0) {
+ /*
+ * The page was marked dirty, but the buffers were
+ * clean. Someone wrote them back by hand with
+ * ll_rw_block/submit_bh. A rare case.
+ */
+ end_page_writeback(page);
+
+ /*
+ * The page and buffer_heads can be released at any time from
+ * here on.
+ */
+ }
+ return err;
+
+recover:
+ /*
+ * ENOSPC, or some other error. We may already have added some
+ * blocks to the file, so we need to write these out to avoid
+ * exposing stale data.
+ * The page is currently locked and not marked for writeback
+ */
+ bh = head;
+ /* Recovery: lock and submit the mapped buffers */
+ do {
+ if (buffer_mapped(bh) && buffer_dirty(bh) &&
+ !buffer_delay(bh)) {
+ lock_buffer(bh);
+ mark_buffer_async_write_endio(bh, handler);
+ } else {
+ /*
+ * The buffer may have been set dirty during
+ * attachment to a dirty page.
+ */
+ clear_buffer_dirty(bh);
+ }
+ } while ((bh = bh->b_this_page) != head);
+ SetPageError(page);
+ BUG_ON(PageWriteback(page));
+ mapping_set_error(page->mapping, err);
+ set_page_writeback(page);
+ do {
+ struct buffer_head *next = bh->b_this_page;
+ if (buffer_async_write(bh)) {
+ clear_buffer_dirty(bh);
+ submit_bh(write_op, bh);
+ nr_underway++;
+ }
+ bh = next;
+ } while (bh != head);
+ unlock_page(page);
+ goto done;
}
/*
--
1.6.0.2
--
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