| Message ID | 20240910125753.80502-1-chao@kernel.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [f2fs-dev] f2fs: fix to tag STATX_DIOALIGN only if inode support dio | expand |
On Tue, Sep 10, 2024 at 08:57:53PM +0800, Chao Yu via Linux-f2fs-devel wrote: > After commit 5c8764f8679e ("f2fs: fix to force buffered IO on inline_data > inode"), f2fs starts to force using buffered IO on inline_data inode. > > And also, it will cause f2fs_getattr() returning invalid zeroed value on > .dio_mem_align and .dio_offset_align fields, however, STATX_DIOALIGN flag > was been tagged. User may use zeroed .stx_dio_offset_align value > since STATX_DIOALIGN was been tagged, then it causes a deadloop during > generic/465 test due to below logic: > > align=stx_dio_offset_align(it equals to zero) > page_size=4096 > while [ $align -le $page_size ]; do > echo "$AIO_TEST -a $align -d $testfile.$align" >> $seqres.full > $AIO_TEST -a $align -d $testfile.$align 2>&1 | tee -a $seqres.full > align=$((align * 2)) > done > > Quoted from description of statx manual: > > " If a filesystem does not support a field or if it has an > unrepresentable value (for instance, a file with an exotic type), > then the mask bit corresponding to that field will be cleared in > stx_mask even if the user asked for it and a dummy value will be > filled in for compatibility purposes if one is available (e.g., > a dummy UID and GID may be specified to mount under some > circumstances)." > > We should not set STATX_DIOALIGN flag in kstat.stx_mask if inode > does not support DIO, so that it can indicate related fields contain > dummy value, and avoid following incorrect use of them. > > Fixes: c8c02272a9f7 ("f2fs: support STATX_DIOALIGN") When claiming to be Fixing a commit, please make sure to Cc the author of that commit. > Signed-off-by: Chao Yu <chao@kernel.org> > --- > fs/f2fs/file.c | 11 ++++------- > 1 file changed, 4 insertions(+), 7 deletions(-) > > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c > index 99903eafa7fe..f0b8b77e93ba 100644 > --- a/fs/f2fs/file.c > +++ b/fs/f2fs/file.c > @@ -906,14 +906,11 @@ int f2fs_getattr(struct mnt_idmap *idmap, const struct path *path, > * f2fs sometimes supports DIO reads but not DIO writes. STATX_DIOALIGN > * cannot represent that, so in that case we report no DIO support. > */ > - if ((request_mask & STATX_DIOALIGN) && S_ISREG(inode->i_mode)) { > - unsigned int bsize = i_blocksize(inode); > - > + if ((request_mask & STATX_DIOALIGN) && S_ISREG(inode->i_mode) && > + !f2fs_force_buffered_io(inode, WRITE)) { > + stat->dio_mem_align = F2FS_BLKSIZE; > + stat->dio_offset_align = F2FS_BLKSIZE; > stat->result_mask |= STATX_DIOALIGN; > - if (!f2fs_force_buffered_io(inode, WRITE)) { > - stat->dio_mem_align = bsize; > - stat->dio_offset_align = bsize; > - } > } > > flags = fi->i_flags; No, this patch is wrong and the existing code is correct. The cases are: STATX_DIOALIGN set and stx_dio_*_align nonzero: File supports DIO. STATX_DIOALIGN set and stx_dio_*_align zero: File doesn't support DIO. STATX_DIOALIGN unset: Filesystem doesn't support STATX_DIOALIGN, so it's unknown whether the file supports DIO or not. Please see the statx(2) manual page which explains this too. - Eric
On 2024/9/11 1:06, Eric Biggers wrote: > On Tue, Sep 10, 2024 at 08:57:53PM +0800, Chao Yu via Linux-f2fs-devel wrote: >> After commit 5c8764f8679e ("f2fs: fix to force buffered IO on inline_data >> inode"), f2fs starts to force using buffered IO on inline_data inode. >> >> And also, it will cause f2fs_getattr() returning invalid zeroed value on >> .dio_mem_align and .dio_offset_align fields, however, STATX_DIOALIGN flag >> was been tagged. User may use zeroed .stx_dio_offset_align value >> since STATX_DIOALIGN was been tagged, then it causes a deadloop during >> generic/465 test due to below logic: >> >> align=stx_dio_offset_align(it equals to zero) >> page_size=4096 >> while [ $align -le $page_size ]; do >> echo "$AIO_TEST -a $align -d $testfile.$align" >> $seqres.full >> $AIO_TEST -a $align -d $testfile.$align 2>&1 | tee -a $seqres.full >> align=$((align * 2)) >> done >> >> Quoted from description of statx manual: >> >> " If a filesystem does not support a field or if it has an >> unrepresentable value (for instance, a file with an exotic type), >> then the mask bit corresponding to that field will be cleared in >> stx_mask even if the user asked for it and a dummy value will be >> filled in for compatibility purposes if one is available (e.g., >> a dummy UID and GID may be specified to mount under some >> circumstances)." >> >> We should not set STATX_DIOALIGN flag in kstat.stx_mask if inode >> does not support DIO, so that it can indicate related fields contain >> dummy value, and avoid following incorrect use of them. >> >> Fixes: c8c02272a9f7 ("f2fs: support STATX_DIOALIGN") > > When claiming to be Fixing a commit, please make sure to Cc the author of that > commit. No problem, will make sure they were Cced. > >> Signed-off-by: Chao Yu <chao@kernel.org> >> --- >> fs/f2fs/file.c | 11 ++++------- >> 1 file changed, 4 insertions(+), 7 deletions(-) >> >> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c >> index 99903eafa7fe..f0b8b77e93ba 100644 >> --- a/fs/f2fs/file.c >> +++ b/fs/f2fs/file.c >> @@ -906,14 +906,11 @@ int f2fs_getattr(struct mnt_idmap *idmap, const struct path *path, >> * f2fs sometimes supports DIO reads but not DIO writes. STATX_DIOALIGN >> * cannot represent that, so in that case we report no DIO support. >> */ >> - if ((request_mask & STATX_DIOALIGN) && S_ISREG(inode->i_mode)) { >> - unsigned int bsize = i_blocksize(inode); >> - >> + if ((request_mask & STATX_DIOALIGN) && S_ISREG(inode->i_mode) && >> + !f2fs_force_buffered_io(inode, WRITE)) { >> + stat->dio_mem_align = F2FS_BLKSIZE; >> + stat->dio_offset_align = F2FS_BLKSIZE; >> stat->result_mask |= STATX_DIOALIGN; >> - if (!f2fs_force_buffered_io(inode, WRITE)) { >> - stat->dio_mem_align = bsize; >> - stat->dio_offset_align = bsize; >> - } >> } >> >> flags = fi->i_flags; > > No, this patch is wrong and the existing code is correct. The cases are: Yes, you're right, thanks for pointing out this! > > STATX_DIOALIGN set and stx_dio_*_align nonzero: > File supports DIO. > > STATX_DIOALIGN set and stx_dio_*_align zero: > File doesn't support DIO. > > STATX_DIOALIGN unset: > Filesystem doesn't support STATX_DIOALIGN, so it's unknown whether the > file supports DIO or not. Above description is clear to me. > > Please see the statx(2) manual page which explains this too. However, below manual seems not very clear about explaining what does it mean about STATX_DIOALIGN is set or not? At least not so clear like above description. stx_dio_mem_align The alignment (in bytes) required for user memory buffers for direct I/O (O_DIRECT) on this file, or 0 if direct I/O is not supported on this file. STATX_DIOALIGN (stx_dio_mem_align and stx_dio_offset_align) is supported on block devices since Linux 6.1. The support on regular files varies by filesystem; it is supported by ext4, f2fs, and xfs since Linux 6.1. stx_dio_offset_align The alignment (in bytes) required for file offsets and I/O segment lengths for direct I/O (O_DIRECT) on this file, or 0 if direct I/O is not supported on this file. This will only be nonzero if stx_dio_mem_align is nonzero, and vice versa. Thanks, > > - Eric
On Wed, Sep 11, 2024 at 11:06:22AM +0800, Chao Yu wrote: > On 2024/9/11 1:06, Eric Biggers wrote: > > On Tue, Sep 10, 2024 at 08:57:53PM +0800, Chao Yu via Linux-f2fs-devel wrote: > > > After commit 5c8764f8679e ("f2fs: fix to force buffered IO on inline_data > > > inode"), f2fs starts to force using buffered IO on inline_data inode. > > > > > > And also, it will cause f2fs_getattr() returning invalid zeroed value on > > > .dio_mem_align and .dio_offset_align fields, however, STATX_DIOALIGN flag > > > was been tagged. User may use zeroed .stx_dio_offset_align value > > > since STATX_DIOALIGN was been tagged, then it causes a deadloop during > > > generic/465 test due to below logic: > > > > > > align=stx_dio_offset_align(it equals to zero) > > > page_size=4096 > > > while [ $align -le $page_size ]; do > > > echo "$AIO_TEST -a $align -d $testfile.$align" >> $seqres.full > > > $AIO_TEST -a $align -d $testfile.$align 2>&1 | tee -a $seqres.full > > > align=$((align * 2)) > > > done > > > > > > Quoted from description of statx manual: > > > > > > " If a filesystem does not support a field or if it has an > > > unrepresentable value (for instance, a file with an exotic type), > > > then the mask bit corresponding to that field will be cleared in > > > stx_mask even if the user asked for it and a dummy value will be > > > filled in for compatibility purposes if one is available (e.g., > > > a dummy UID and GID may be specified to mount under some > > > circumstances)." > > > > > > We should not set STATX_DIOALIGN flag in kstat.stx_mask if inode > > > does not support DIO, so that it can indicate related fields contain > > > dummy value, and avoid following incorrect use of them. > > > > > > Fixes: c8c02272a9f7 ("f2fs: support STATX_DIOALIGN") > > > > When claiming to be Fixing a commit, please make sure to Cc the author of that > > commit. > > No problem, will make sure they were Cced. > > > > > > Signed-off-by: Chao Yu <chao@kernel.org> > > > --- > > > fs/f2fs/file.c | 11 ++++------- > > > 1 file changed, 4 insertions(+), 7 deletions(-) > > > > > > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c > > > index 99903eafa7fe..f0b8b77e93ba 100644 > > > --- a/fs/f2fs/file.c > > > +++ b/fs/f2fs/file.c > > > @@ -906,14 +906,11 @@ int f2fs_getattr(struct mnt_idmap *idmap, const struct path *path, > > > * f2fs sometimes supports DIO reads but not DIO writes. STATX_DIOALIGN > > > * cannot represent that, so in that case we report no DIO support. > > > */ > > > - if ((request_mask & STATX_DIOALIGN) && S_ISREG(inode->i_mode)) { > > > - unsigned int bsize = i_blocksize(inode); > > > - > > > + if ((request_mask & STATX_DIOALIGN) && S_ISREG(inode->i_mode) && > > > + !f2fs_force_buffered_io(inode, WRITE)) { > > > + stat->dio_mem_align = F2FS_BLKSIZE; > > > + stat->dio_offset_align = F2FS_BLKSIZE; > > > stat->result_mask |= STATX_DIOALIGN; > > > - if (!f2fs_force_buffered_io(inode, WRITE)) { > > > - stat->dio_mem_align = bsize; > > > - stat->dio_offset_align = bsize; > > > - } > > > } > > > flags = fi->i_flags; > > > > No, this patch is wrong and the existing code is correct. The cases are: > > Yes, you're right, thanks for pointing out this! > > > > > STATX_DIOALIGN set and stx_dio_*_align nonzero: > > File supports DIO. > > > > STATX_DIOALIGN set and stx_dio_*_align zero: > > File doesn't support DIO. > > > > STATX_DIOALIGN unset: > > Filesystem doesn't support STATX_DIOALIGN, so it's unknown whether the > > file supports DIO or not. > > Above description is clear to me. > > > > > Please see the statx(2) manual page which explains this too. > > However, below manual seems not very clear about explaining what does it > mean about STATX_DIOALIGN is set or not? At least not so clear like above > description. > It just works the same way that the other statx mask bits work. See the following paragraph: If a filesystem does not support a field or if it has an unrepresentable value (for instance, a file with an exotic type), then the mask bit corresponding to that field will be cleared in stx_mask even if the user asked for it and a dummy value will be filled in for compatibility purposes if one is available (e.g., a dummy UID and GID may be specified to mount under some circumstances). It might be worth an explicit note in the documentation for stx_dio_mem_align, but I considered it to be covered by the above. - Eric
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c index 99903eafa7fe..f0b8b77e93ba 100644 --- a/fs/f2fs/file.c +++ b/fs/f2fs/file.c @@ -906,14 +906,11 @@ int f2fs_getattr(struct mnt_idmap *idmap, const struct path *path, * f2fs sometimes supports DIO reads but not DIO writes. STATX_DIOALIGN * cannot represent that, so in that case we report no DIO support. */ - if ((request_mask & STATX_DIOALIGN) && S_ISREG(inode->i_mode)) { - unsigned int bsize = i_blocksize(inode); - + if ((request_mask & STATX_DIOALIGN) && S_ISREG(inode->i_mode) && + !f2fs_force_buffered_io(inode, WRITE)) { + stat->dio_mem_align = F2FS_BLKSIZE; + stat->dio_offset_align = F2FS_BLKSIZE; stat->result_mask |= STATX_DIOALIGN; - if (!f2fs_force_buffered_io(inode, WRITE)) { - stat->dio_mem_align = bsize; - stat->dio_offset_align = bsize; - } } flags = fi->i_flags;
After commit 5c8764f8679e ("f2fs: fix to force buffered IO on inline_data inode"), f2fs starts to force using buffered IO on inline_data inode. And also, it will cause f2fs_getattr() returning invalid zeroed value on .dio_mem_align and .dio_offset_align fields, however, STATX_DIOALIGN flag was been tagged. User may use zeroed .stx_dio_offset_align value since STATX_DIOALIGN was been tagged, then it causes a deadloop during generic/465 test due to below logic: align=stx_dio_offset_align(it equals to zero) page_size=4096 while [ $align -le $page_size ]; do echo "$AIO_TEST -a $align -d $testfile.$align" >> $seqres.full $AIO_TEST -a $align -d $testfile.$align 2>&1 | tee -a $seqres.full align=$((align * 2)) done Quoted from description of statx manual: " If a filesystem does not support a field or if it has an unrepresentable value (for instance, a file with an exotic type), then the mask bit corresponding to that field will be cleared in stx_mask even if the user asked for it and a dummy value will be filled in for compatibility purposes if one is available (e.g., a dummy UID and GID may be specified to mount under some circumstances)." We should not set STATX_DIOALIGN flag in kstat.stx_mask if inode does not support DIO, so that it can indicate related fields contain dummy value, and avoid following incorrect use of them. Fixes: c8c02272a9f7 ("f2fs: support STATX_DIOALIGN") Signed-off-by: Chao Yu <chao@kernel.org> --- fs/f2fs/file.c | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-)