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Groups > linux.kernel > #1339840
| From | Ross Zwisler <ross.zwisler@linux.intel.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [PATCH v4 3/5] ext4: Online defrag not supported with DAX |
| Date | 2016-02-22 20:10 +0100 |
| Message-ID | <r541Q-1YW-33@gated-at.bofh.it> (permalink) |
| References | <r53Sa-1FT-15@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
Online defrag operations for ext4 are hard coded to use the page cache.
See ext4_ioctl() -> ext4_move_extents() -> move_extent_per_page()
When combined with DAX I/O, which circumvents the page cache, this can
result in data corruption. This was observed with xfstests ext4/307 and
ext4/308.
Fix this by only allowing online defrag for non-DAX files.
Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
---
fs/ext4/ioctl.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index a99b010..eae5917 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -583,6 +583,11 @@ group_extend_out:
"Online defrag not supported with bigalloc");
err = -EOPNOTSUPP;
goto mext_out;
+ } else if (IS_DAX(inode)) {
+ ext4_msg(sb, KERN_ERR,
+ "Online defrag not supported with DAX");
+ err = -EOPNOTSUPP;
+ goto mext_out;
}
err = mnt_want_write_file(filp);
--
2.5.0
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[PATCH v4 0/5] DAX fixes, move flushing calls to FS Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-02-22 20:00 +0100 [PATCH v4 5/5] dax: move writeback calls into the filesystems Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-02-22 20:00 +0100 [PATCH v4 1/5] block: disable block device DAX by default Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-02-22 20:10 +0100 [PATCH v4 2/5] ext2, ext4: only set S_DAX for regular inodes Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-02-22 20:10 +0100 [PATCH v4 3/5] ext4: Online defrag not supported with DAX Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-02-22 20:10 +0100 [PATCH v4 4/5] dax: give DAX clearing code correct bdev Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-02-22 20:10 +0100
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