ext4: remove EXT4_EOFBLOCKS_FL and associated code

The EXT4_EOFBLOCKS_FL inode flag is used to indicate whether a file
contains unwritten blocks past i_size.  It's set when ext4_fallocate
is called with the KEEP_SIZE flag to extend a file with an unwritten
extent.  However, this flag hasn't been useful functionally since
March, 2012, when a decision was made to remove it from ext4.

All traces of EXT4_EOFBLOCKS_FL were removed from e2fsprogs version
1.42.2 by commit 010dc7b90d97 ("e2fsck: remove EXT4_EOFBLOCKS_FL flag
handling") at that time.  Now that enough time has passed to make
e2fsprogs versions containing this modification common, this patch now
removes the code associated with EXT4_EOFBLOCKS_FL from the kernel as
well.

This change has two implications.  First, because pre-1.42.2 e2fsck
versions only look for a problem if EXT4_EOFBLOCKS_FL is set, and
because that bit will never be set by newer kernels containing this
patch, old versions of e2fsck won't have a compatibility problem with
files created by newer kernels.

Second, newer kernels will not clear EXT4_EOFBLOCKS_FL inode flag bits
belonging to a file written by an older kernel.  If set, it will remain
in that state until the file is deleted.  Because e2fsck versions since
1.42.2 don't check the flag at all, no adverse effect is expected.
However, pre-1.42.2 e2fsck versions that do check the flag may report
that it is set when it ought not to be after a file has been truncated
or had its unwritten blocks written.  In this case, the old version of
e2fsck will offer to clear the flag.  No adverse effect would then
occur whether the user chooses to clear the flag or not.

Signed-off-by: Eric Whitney <enwlinux@gmail.com>
Link: https://lore.kernel.org/r/20200211210216.24960-1-enwlinux@gmail.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

1 files changed, 2 insertions, 3 deletions

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 61b37a052052..54f0a003053b 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -414,7 +414,7 @@ struct flex_groups {
 #define EXT4_EXTENTS_FL			0x00080000 /* Inode uses extents */
 #define EXT4_VERITY_FL			0x00100000 /* Verity protected inode */
 #define EXT4_EA_INODE_FL	        0x00200000 /* Inode used for large EA */
-#define EXT4_EOFBLOCKS_FL		0x00400000 /* Blocks allocated beyond EOF */
+/* 0x00400000 was formerly EXT4_EOFBLOCKS_FL */
 #define EXT4_INLINE_DATA_FL		0x10000000 /* Inode has inline data. */
 #define EXT4_PROJINHERIT_FL		0x20000000 /* Create with parents projid */
 #define EXT4_CASEFOLD_FL		0x40000000 /* Casefolded file */
@@ -487,7 +487,7 @@ enum {
 	EXT4_INODE_EXTENTS	= 19,	/* Inode uses extents */
 	EXT4_INODE_VERITY	= 20,	/* Verity protected inode */
 	EXT4_INODE_EA_INODE	= 21,	/* Inode used for large EA */
-	EXT4_INODE_EOFBLOCKS	= 22,	/* Blocks allocated beyond EOF */
+/* 22 was formerly EXT4_INODE_EOFBLOCKS */
 	EXT4_INODE_INLINE_DATA	= 28,	/* Data in inode. */
 	EXT4_INODE_PROJINHERIT	= 29,	/* Create with parents projid */
 	EXT4_INODE_RESERVED	= 31,	/* reserved for ext4 lib */
@@ -533,7 +533,6 @@ static inline void ext4_check_flag_values(void)
 	CHECK_FLAG_VALUE(EXTENTS);
 	CHECK_FLAG_VALUE(VERITY);
 	CHECK_FLAG_VALUE(EA_INODE);
-	CHECK_FLAG_VALUE(EOFBLOCKS);
 	CHECK_FLAG_VALUE(INLINE_DATA);
 	CHECK_FLAG_VALUE(PROJINHERIT);
 	CHECK_FLAG_VALUE(RESERVED);