jbd2: mark the transaction context with the scope GFP_NOFS context

now that we have memalloc_nofs_{save,restore} api we can mark the whole
transaction context as implicitly GFP_NOFS.  All allocations will
automatically inherit GFP_NOFS this way.  This means that we do not have
to mark any of those requests with GFP_NOFS and moreover all the
ext4_kv[mz]alloc(GFP_NOFS) are also safe now because even the hardcoded
GFP_KERNEL allocations deep inside the vmalloc will be NOFS now.

[akpm@linux-foundation.org: tweak comments]
Link: http://lkml.kernel.org/r/20170306131408.9828-7-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Chris Mason <clm@fb.com>
Cc: David Sterba <dsterba@suse.cz>
Cc: Brian Foster <bfoster@redhat.com>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Cc: Nikolay Borisov <nborisov@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index 5e659ee..9ee4832 100644 (file)
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -29,6 +29,7 @@
 #include <linux/backing-dev.h>
 #include <linux/bug.h>
 #include <linux/module.h>
+#include <linux/sched/mm.h>
 
 #include <trace/events/jbd2.h>
 
@@ -388,6 +389,11 @@ repeat:
 
        rwsem_acquire_read(&journal->j_trans_commit_map, 0, 0, _THIS_IP_);
        jbd2_journal_free_transaction(new_transaction);
+       /*
+        * Ensure that no allocations done while the transaction is open are
+        * going to recurse back to the fs layer.
+        */
+       handle->saved_alloc_context = memalloc_nofs_save();
        return 0;
 }
 
@@ -466,6 +472,7 @@ handle_t *jbd2__journal_start(journal_t *journal, int nblocks, int rsv_blocks,
        trace_jbd2_handle_start(journal->j_fs_dev->bd_dev,
                                handle->h_transaction->t_tid, type,
                                line_no, nblocks);
+
        return handle;
 }
 EXPORT_SYMBOL(jbd2__journal_start);
@@ -1760,6 +1767,11 @@ int jbd2_journal_stop(handle_t *handle)
        if (handle->h_rsv_handle)
                jbd2_journal_free_reserved(handle->h_rsv_handle);
 free_and_exit:
+       /*
+        * Scope of the GFP_NOFS context is over here and so we can restore the
+        * original alloc context.
+        */
+       memalloc_nofs_restore(handle->saved_alloc_context);
        jbd2_free_handle(handle);
        return err;
 }

diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index dfaa1f4..606b6bc 100644 (file)
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -491,6 +491,8 @@ struct jbd2_journal_handle
 
        unsigned long           h_start_jiffies;
        unsigned int            h_requested_credits;
+
+       unsigned int            saved_alloc_context;
 };