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Message-ID: <5F1F7B88.40001@cn.fujitsu.com> Date: Tue, 28 Jul 2020 09:12:40 +0800 From: Xiao Yang <yangx.jy@...fujitsu.com> To: "Darrick J. Wong" <darrick.wong@...cle.com> CC: <ira.weiny@...el.com>, <tytso@....edu>, <linux-ext4@...r.kernel.org> Subject: Re: [PATCH] chattr/lsattr: Support dax attribute 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@...fujitsu.com> >> --- >> 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 >> >> >> > > . >
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