block_write_full_page: Use synchronous writes for WBC_SYNC_ALL writebacks

When doing synchronous writes because wbc->sync_mode is set to
WBC_SYNC_ALL, send the write request using WRITE_SYNC, so that we
don't unduly block system calls such as fsync().

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Acked-by: Jan Kara <jack@suse.cz>

diff --git a/fs/buffer.c b/fs/buffer.c
index 891e1c7..e7ebd95 100644 (file)
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1714,6 +1714,7 @@ static int __block_write_full_page(struct inode *inode, struct page *page,
        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 : WRITE);
 
        BUG_ON(!PageLocked(page));
 
@@ -1805,7 +1806,7 @@ static int __block_write_full_page(struct inode *inode, struct page *page,
        do {
                struct buffer_head *next = bh->b_this_page;
                if (buffer_async_write(bh)) {
-                       submit_bh(WRITE, bh);
+                       submit_bh(write_op, bh);
                        nr_underway++;
                }
                bh = next;
@@ -1859,7 +1860,7 @@ recover:
                struct buffer_head *next = bh->b_this_page;
                if (buffer_async_write(bh)) {
                        clear_buffer_dirty(bh);
-                       submit_bh(WRITE, bh);
+                       submit_bh(write_op, bh);
                        nr_underway++;
                }
                bh = next;