Hi Darrick, Thanks for your review. On 2020/7/28 0:08, Darrick J. Wong wrote:
On Mon, Jul 27, 2020 at 05:29:01PM +0800, Xiao Yang wrote:Use the letter 'x' to set/get dax attribute on a directory/file. Signed-off-by: Xiao Yang<yangx.jy@xxxxxxxxxxxxxx> --- lib/e2p/pf.c | 1 + lib/ext2fs/ext2_fs.h | 1 + misc/chattr.1.in | 10 ++++++++-- misc/chattr.c | 3 ++- 4 files changed, 12 insertions(+), 3 deletions(-) diff --git a/lib/e2p/pf.c b/lib/e2p/pf.c index 0c6998c4..e59cccff 100644 --- a/lib/e2p/pf.c +++ b/lib/e2p/pf.c @@ -44,6 +44,7 @@ static struct flags_name flags_array[] = { { EXT2_TOPDIR_FL, "T", "Top_of_Directory_Hierarchies" }, { EXT4_EXTENTS_FL, "e", "Extents" }, { FS_NOCOW_FL, "C", "No_COW" }, + { FS_DAX_FL, "x", "Dax" }, { EXT4_CASEFOLD_FL, "F", "Casefold" }, { EXT4_INLINE_DATA_FL, "N", "Inline_Data" }, { EXT4_PROJINHERIT_FL, "P", "Project_Hierarchy" }, diff --git a/lib/ext2fs/ext2_fs.h b/lib/ext2fs/ext2_fs.h index 6c20ea77..b5e2e42a 100644 --- a/lib/ext2fs/ext2_fs.h +++ b/lib/ext2fs/ext2_fs.h @@ -334,6 +334,7 @@ struct ext2_dx_tail { #define EXT4_EA_INODE_FL 0x00200000 /* Inode used for large EA */ /* EXT4_EOFBLOCKS_FL 0x00400000 was here */ #define FS_NOCOW_FL 0x00800000 /* Do not cow file */ +#define FS_DAX_FL 0x02000000 /* Inode is DAX */ #define EXT4_SNAPFILE_FL 0x01000000 /* Inode is a snapshot */ #define EXT4_SNAPFILE_DELETED_FL 0x04000000 /* Snapshot is being deleted */ #define EXT4_SNAPFILE_SHRUNK_FL 0x08000000 /* Snapshot shrink has completed */ diff --git a/misc/chattr.1.in b/misc/chattr.1.in index ff2fcf00..b27c8e1f 100644 --- a/misc/chattr.1.in +++ b/misc/chattr.1.in @@ -23,7 +23,7 @@ chattr \- change file attributes on a Linux file system .B chattr changes the file attributes on a Linux file system. .PP -The format of a symbolic mode is +-=[aAcCdDeFijPsStTu]. +The format of a symbolic mode is +-=[aAcCdDeFijPsStTux]. .PP The operator '+' causes the selected attributes to be added to the existing attributes of the files; '-' causes them to be removed; and '=' @@ -45,7 +45,8 @@ secure deletion (s), synchronous updates (S), no tail-merging (t), top of directory hierarchy (T), -and undeletable (u). +undeletable (u), +and direct access for files (x). .PP The following attributes are read-only, and may be listed by .BR lsattr (1) @@ -210,6 +211,11 @@ saved. This allows the user to ask for its undeletion. Note: please make sure to read the bugs and limitations section at the end of this document. .TP +.B x +A file with the 'x' attribute set is accessed directly on the memory-like +disk(e.g. /dev/pmem) by the kernel. Kernel will skip page cache and do +reads/writes on the file directly.There's much more to FS_DAX_FL than that.
Agreed. Sorry for the rough description.
See the "Enabling DAX on XFS and ext4" section of Documentation/filesystems/dax.txt. Note the part where you can set it on directories too; and also the part where there's a separate state for whether or not you get the pagecache bypass.
I will try to add more detailed description in v2 patch. Thanks, Xiao Yang
--D+.TP .B V A file with the 'V' attribute set has fs-verity enabled. It cannot be written to, and the filesystem will automatically verify all data read diff --git a/misc/chattr.c b/misc/chattr.c index a5d60170..c0337f86 100644 --- a/misc/chattr.c +++ b/misc/chattr.c @@ -86,7 +86,7 @@ static unsigned long sf; static void usage(void) { fprintf(stderr, - _("Usage: %s [-pRVf] [-+=aAcCdDeijPsStTuF] [-v version] files...\n"), + _("Usage: %s [-pRVf] [-+=aAcCdDeijPsStTuFx] [-v version] files...\n"), program_name); exit(1); } @@ -112,6 +112,7 @@ static const struct flags_char flags_array[] = { { EXT2_NOTAIL_FL, 't' }, { EXT2_TOPDIR_FL, 'T' }, { FS_NOCOW_FL, 'C' }, + { FS_DAX_FL, 'x' }, { EXT4_CASEFOLD_FL, 'F' }, { 0, 0 } }; -- 2.21.0.
