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Wong" Cc: Nirjhar Roy , fstests@vger.kernel.org, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, ojaswin@linux.ibm.com, zlang@kernel.org Subject: Re: [PATCH v2 1/2] common/rc,xfs/207: Adding a common helper function to check xflag bits on a given file In-Reply-To: <20241118162810.GI9425@frogsfrogsfrogs> Date: Mon, 18 Nov 2024 23:36:12 +0530 Message-ID: <87r0788lij.fsf@gmail.com> References: <9a955f34cab443d3ed0fc07c17886d5e8a11ad80.1731597226.git.nirjhar@linux.ibm.com> <20241115164548.GE9425@frogsfrogsfrogs> <87r07cco5p.fsf@gmail.com> <20241118162810.GI9425@frogsfrogsfrogs> Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: "Darrick J. Wong" writes: > On Sat, Nov 16, 2024 at 12:36:26AM +0530, Ritesh Harjani wrote: >> "Darrick J. Wong" writes: >> >> > On Fri, Nov 15, 2024 at 09:45:58AM +0530, Nirjhar Roy wrote: >> >> This patch defines a common helper function to test whether any of >> >> fsxattr xflags field is set or not. We will use this helper in the next >> >> patch for checking extsize (e) flag. >> >> >> >> Reviewed-by: Ritesh Harjani (IBM) >> >> Reviewed-by: Ojaswin Mujoo >> >> Signed-off-by: Nirjhar Roy >> >> --- >> >> common/rc | 7 +++++++ >> >> tests/xfs/207 | 13 ++----------- >> >> 2 files changed, 9 insertions(+), 11 deletions(-) >> >> >> >> diff --git a/common/rc b/common/rc >> >> index 2af26f23..fc18fc94 100644 >> >> --- a/common/rc >> >> +++ b/common/rc >> >> @@ -41,6 +41,13 @@ _md5_checksum() >> >> md5sum $1 | cut -d ' ' -f1 >> >> } >> >> >> >> +# Check whether a fsxattr xflags character ($2) field is set on a given file ($1). >> >> +# e.g, fsxattr.xflags = 0x80000800 [----------e-----X] >> >> +_test_fsx_xflags_field() >> > >> > How about we call this "_test_fsxattr_xflag" instead? >> > >> > fsx is already something else in fstests. >> > >> >> +{ >> >> + grep -q "fsxattr.xflags.*\[.*$2.*\]" <($XFS_IO_PROG -c "stat" "$1") >> >> +} >> > >> > Not sure why this lost the xfs_io | grep -q structure. The return value >> > of the whole expression will always be the return value of the last >> > command in the pipeline. >> > >> >> I guess it was suggested here [1] >> >> [1]: https://lore.kernel.org/all/20241025025651.okneano7d324nl4e@dell-per750-06-vm-08.rhts.eng.pek2.redhat.com/ > > Ah. > >> root-> grep -q "hello" <(echo "hello world"); echo $? >> 0 >> >> The cmd is not using the unnamed pipes ("|") any more. It's spawning the >> process () which does echo "hello world" and creating a named pipe or >> say temporary FD <() which is being read by grep now. So we still will >> have the correct return value. Slightly inefficitent compared to unnamed >> pipes though I agree. > > Well... it's subtle, being bash, right? :) > > bash creates a pipe and a subprocess for the "echo hello world", then > hooks its stdout to the pipe, just like a regular "|" pipe. > > But for "grep -q hello" things are different -- for the grep process, > the pipe is added as a new fd (e.g. /dev/fd/63), and then that path is > provided on the command line. So what bash is doing is: > > grep -q "hello" /dev/fd/63 > > AFAICT for grep this makes no difference unless you want it to tell you > filenames: > > $ grep -l hello <(echo hello world) > /dev/fd/63 aah yes, I see (from strace) pipe2([3, 4], 0) = 0 fcntl(63, F_GETFD) = 0 fcntl(62, F_GETFD) = -1 EBADF (Bad file descriptor) dup2(3, 62) = 62 close(3) = 0 Thanks! -ritesh > $ echo hello world | grep -l hello > (standard input) > > and I'm sure there's other weird implications that I'm not remembering. > >> > (Correct? I hate bash...) >> > >> >> root-> ls -la <(echo "hello world"); >> lr-x------ 1 root root 64 Nov 16 00:42 /dev/fd/63 -> 'pipe:[74211850]' >> >> Did I make you hate it more? ;) > > Yep! > > --D > >> >> -ritesh >> >> > --D >> > >> >> + >> >> # Write a byte into a range of a file >> >> _pwrite_byte() { >> >> local pattern="$1" >> >> diff --git a/tests/xfs/207 b/tests/xfs/207 >> >> index bbe21307..4f6826f3 100755 >> >> --- a/tests/xfs/207 >> >> +++ b/tests/xfs/207 >> >> @@ -21,15 +21,6 @@ _require_cp_reflink >> >> _require_xfs_io_command "fiemap" >> >> _require_xfs_io_command "cowextsize" >> >> >> >> -# Takes the fsxattr.xflags line, >> >> -# i.e. fsxattr.xflags = 0x0 [--------------C-] >> >> -# and tests whether a flag character is set >> >> -test_xflag() >> >> -{ >> >> - local flg=$1 >> >> - grep -q "\[.*${flg}.*\]" && echo "$flg flag set" || echo "$flg flag unset" >> >> -} >> >> - >> >> echo "Format and mount" >> >> _scratch_mkfs > $seqres.full 2>&1 >> >> _scratch_mount >> $seqres.full 2>&1 >> >> @@ -65,14 +56,14 @@ echo "Set cowextsize and check flag" >> >> $XFS_IO_PROG -c "cowextsize 1048576" $testdir/file3 | _filter_scratch >> >> _scratch_cycle_mount >> >> >> >> -$XFS_IO_PROG -c "stat" $testdir/file3 | grep 'fsxattr.xflags' | test_xflag "C" >> >> +_test_fsx_xflags_field "$testdir/file3" "C" && echo "C flag set" || echo "C flag unset" >> >> $XFS_IO_PROG -c "cowextsize" $testdir/file3 | _filter_scratch >> >> >> >> echo "Unset cowextsize and check flag" >> >> $XFS_IO_PROG -c "cowextsize 0" $testdir/file3 | _filter_scratch >> >> _scratch_cycle_mount >> >> >> >> -$XFS_IO_PROG -c "stat" $testdir/file3 | grep 'fsxattr.xflags' | test_xflag "C" >> >> +_test_fsx_xflags_field "$testdir/file3" "C" && echo "C flag set" || echo "C flag unset" >> >> $XFS_IO_PROG -c "cowextsize" $testdir/file3 | _filter_scratch >> >> >> >> status=0 >> >> -- >> >> 2.43.5 >> >> >> >> >>