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Date:   Thu,  9 Sep 2021 20:23:34 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Theodore Ts'o <tytso@....edu>, yangerkun <yangerkun@...wei.com>,
        Sasha Levin <sashal@...nel.org>, linux-ext4@...r.kernel.org
Subject: [PATCH AUTOSEL 4.9 13/17] ext4: if zeroout fails fall back to splitting the extent node

From: Theodore Ts'o <tytso@....edu>

[ Upstream commit 308c57ccf4318236be75dfa251c84713e694457b ]

If the underlying storage device is using thin-provisioning, it's
possible for a zeroout operation to return ENOSPC.

Commit df22291ff0fd ("ext4: Retry block allocation if we have free blocks
left") added logic to retry block allocation since we might get free block
after we commit a transaction. But the ENOSPC from thin-provisioning
will confuse ext4, and lead to an infinite loop.

Since using zeroout instead of splitting the extent node is an
optimization, if it fails, we might as well fall back to splitting the
extent node.

Reported-by: yangerkun <yangerkun@...wei.com>
Signed-off-by: Theodore Ts'o <tytso@....edu>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/ext4/extents.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index d195f41071d8..851ccbc01138 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -3636,7 +3636,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
 				split_map.m_len - ee_block);
 			err = ext4_ext_zeroout(inode, &zero_ex1);
 			if (err)
-				goto out;
+				goto fallback;
 			split_map.m_len = allocated;
 		}
 		if (split_map.m_lblk - ee_block + split_map.m_len <
@@ -3650,7 +3650,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
 						      ext4_ext_pblock(ex));
 				err = ext4_ext_zeroout(inode, &zero_ex2);
 				if (err)
-					goto out;
+					goto fallback;
 			}
 
 			split_map.m_len += split_map.m_lblk - ee_block;
@@ -3659,6 +3659,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
 		}
 	}
 
+fallback:
 	err = ext4_split_extent(handle, inode, ppath, &split_map, split_flag,
 				flags);
 	if (err > 0)
-- 
2.30.2

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