btrfs: zoned: only allow one process to add pages to a relocation inode

Don't allow more than one process to add pages to a relocation inode on
a zoned filesystem, otherwise we cannot guarantee the sequential write
rule once we're filling preallocated extents on a zoned filesystem.

Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 8959ac580f4661e8caa9500b177b98f96ddd40ef..cb366f6bcaedec34fbf944cf00eab55bb05ba8d2 100644 (file)
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -5132,6 +5132,9 @@ int extent_write_locked_range(struct inode *inode, u64 start, u64 end,
 int extent_writepages(struct address_space *mapping,
                      struct writeback_control *wbc)
 {
+       struct inode *inode = mapping->host;
+       const bool data_reloc = btrfs_is_data_reloc_root(BTRFS_I(inode)->root);
+       const bool zoned = btrfs_is_zoned(BTRFS_I(inode)->root->fs_info);
        int ret = 0;
        struct extent_page_data epd = {
                .bio_ctrl = { 0 },
@@ -5139,7 +5142,15 @@ int extent_writepages(struct address_space *mapping,
                .sync_io = wbc->sync_mode == WB_SYNC_ALL,
        };
 
+       /*
+        * Allow only a single thread to do the reloc work in zoned mode to
+        * protect the write pointer updates.
+        */
+       if (data_reloc && zoned)
+               btrfs_inode_lock(inode, 0);
        ret = extent_write_cache_pages(mapping, wbc, &epd);
+       if (data_reloc && zoned)
+               btrfs_inode_unlock(inode, 0);
        ASSERT(ret <= 0);
        if (ret < 0) {
                end_write_bio(&epd, ret);