linux-kernel - [PATCH v2 3/9] mm: clear any AS_* errors when returning error on any fsync or close

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Date:   Wed,  8 Mar 2017 11:29:28 -0500
From:   Jeff Layton <jlayton@...hat.com>
To:     viro@...iv.linux.org.uk, akpm@...ux-foundation.org
Cc:     konishi.ryusuke@....ntt.co.jp, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-nilfs@...r.kernel.org, ross.zwisler@...ux.intel.com,
        jack@...e.cz, neilb@...e.com, openosd@...il.com, adilger@...ger.ca,
        James.Bottomley@...senPartnership.com
Subject: [PATCH v2 3/9] mm: clear any AS_* errors when returning error on any fsync or close

Currently we don't clear the address space error when there is a -EIO
error on fsynci, due to writeback initiation failure. If writes fail
with -EIO and the mapping is flagged with an AS_EIO or AS_ENOSPC error,
then we can end up returning errors on two fsync calls, even when a
write between them succeeded (or there was no write).

Ensure that we also clear out any mapping errors when initiating
writeback fails with -EIO in filemap_write_and_wait and
filemap_write_and_wait_range.

Suggested-by: Jan Kara <jack@...e.cz>
Signed-off-by: Jeff Layton <jlayton@...hat.com>
---
 mm/filemap.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 1694623a6289..fc123b9833e1 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -488,7 +488,7 @@ EXPORT_SYMBOL(filemap_fdatawait);
 
 int filemap_write_and_wait(struct address_space *mapping)
 {
-	int err = 0;
+	int err;
 
 	if ((!dax_mapping(mapping) && mapping->nrpages) ||
 	    (dax_mapping(mapping) && mapping->nrexceptional)) {
@@ -499,10 +499,18 @@ int filemap_write_and_wait(struct address_space *mapping)
 		 * But the -EIO is special case, it may indicate the worst
 		 * thing (e.g. bug) happened, so we avoid waiting for it.
 		 */
-		if (err != -EIO) {
+		if (likely(err != -EIO)) {
 			int err2 = filemap_fdatawait(mapping);
 			if (!err)
 				err = err2;
+		} else {
+			/*
+			 * Clear the error in the address space since we're
+			 * returning an error here. -EIO takes precedence over
+			 * everything else though, so we can just discard
+			 * the return here.
+			 */
+			filemap_check_errors(mapping);
 		}
 	} else {
 		err = filemap_check_errors(mapping);
@@ -537,6 +545,14 @@ int filemap_write_and_wait_range(struct address_space *mapping,
 						lstart, lend);
 			if (!err)
 				err = err2;
+		} else {
+			/*
+			 * Clear the error in the address space since we're
+			 * returning an error here. -EIO takes precedence over
+			 * everything else though, so we can just discard
+			 * the return here.
+			 */
+			filemap_check_errors(mapping);
 		}
 	} else {
 		err = filemap_check_errors(mapping);
-- 
2.9.3