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authorJan Kara <jack@suse.cz>2013-08-17 18:09:31 +0400
committerTheodore Ts'o <tytso@mit.edu>2013-08-17 18:09:31 +0400
commit90e775b71ac4e685898c7995756fe58c135adaa6 (patch)
treee7e84b7990ad61717808830726b0fce4e9c0464a /fs/ext4/ext4.h
parent5208386c501276df18fee464e21d3c58d2d79517 (diff)
downloadlinux-90e775b71ac4e685898c7995756fe58c135adaa6.tar.xz
ext4: fix lost truncate due to race with writeback
The following race can lead to a loss of i_disksize update from truncate thus resulting in a wrong inode size if the inode size isn't updated again before inode is reclaimed: ext4_setattr() mpage_map_and_submit_extent() EXT4_I(inode)->i_disksize = attr->ia_size; ... ... disksize = ((loff_t)mpd->first_page) << PAGE_CACHE_SHIFT /* False because i_size isn't * updated yet */ if (disksize > i_size_read(inode)) /* True, because i_disksize is * already truncated */ if (disksize > EXT4_I(inode)->i_disksize) /* Overwrite i_disksize * update from truncate */ ext4_update_i_disksize() i_size_write(inode, attr->ia_size); For other places updating i_disksize such race cannot happen because i_mutex prevents these races. Writeback is the only place where we do not hold i_mutex and we cannot grab it there because of lock ordering. We fix the race by doing both i_disksize and i_size update in truncate atomically under i_data_sem and in mpage_map_and_submit_extent() we move the check against i_size under i_data_sem as well. Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> Cc: stable@vger.kernel.org
Diffstat (limited to 'fs/ext4/ext4.h')
-rw-r--r--fs/ext4/ext4.h24
1 files changed, 20 insertions, 4 deletions
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 58dede76f75f..3dbc56eb4849 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2432,16 +2432,32 @@ do { \
#define EXT4_FREECLUSTERS_WATERMARK 0
#endif
+/* Update i_disksize. Requires i_mutex to avoid races with truncate */
static inline void ext4_update_i_disksize(struct inode *inode, loff_t newsize)
{
- /*
- * XXX: replace with spinlock if seen contended -bzzz
- */
+ WARN_ON_ONCE(S_ISREG(inode->i_mode) &&
+ !mutex_is_locked(&inode->i_mutex));
+ down_write(&EXT4_I(inode)->i_data_sem);
+ if (newsize > EXT4_I(inode)->i_disksize)
+ EXT4_I(inode)->i_disksize = newsize;
+ up_write(&EXT4_I(inode)->i_data_sem);
+}
+
+/*
+ * Update i_disksize after writeback has been started. Races with truncate
+ * are avoided by checking i_size under i_data_sem.
+ */
+static inline void ext4_wb_update_i_disksize(struct inode *inode, loff_t newsize)
+{
+ loff_t i_size;
+
down_write(&EXT4_I(inode)->i_data_sem);
+ i_size = i_size_read(inode);
+ if (newsize > i_size)
+ newsize = i_size;
if (newsize > EXT4_I(inode)->i_disksize)
EXT4_I(inode)->i_disksize = newsize;
up_write(&EXT4_I(inode)->i_data_sem);
- return ;
}
struct ext4_group_info {