| Message ID | 20240930125438.2501050-7-john.g.garry@oracle.com (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
| Series | block atomic writes for xfs | expand |
On Mon, Sep 30, 2024 at 12:54:37PM +0000, John Garry wrote: > Validate that an atomic write adheres to length/offset rules. Currently > we can only write a single FS block. > > For an IOCB with IOCB_ATOMIC set to get as far as xfs_file_dio_write(), > FMODE_CAN_ATOMIC_WRITE will need to be set for the file; for this, > ATOMICWRITES flags would also need to be set for the inode. > > Signed-off-by: John Garry <john.g.garry@oracle.com> > --- > fs/xfs/xfs_file.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c > index 412b1d71b52b..fa6a44b88ecc 100644 > --- a/fs/xfs/xfs_file.c > +++ b/fs/xfs/xfs_file.c > @@ -688,6 +688,13 @@ xfs_file_dio_write( > struct xfs_buftarg *target = xfs_inode_buftarg(ip); > size_t count = iov_iter_count(from); > > + if (iocb->ki_flags & IOCB_ATOMIC) { > + if (count != ip->i_mount->m_sb.sb_blocksize) > + return -EINVAL; > + if (!generic_atomic_write_valid(iocb, from)) > + return -EINVAL; > + } Does xfs_file_write_iter need a catch-all so that we don't fall back to buffered write for a directio write that returns ENOTBLK? if (iocb->ki_flags & IOCB_DIRECT) { /* * Allow a directio write to fall back to a buffered * write *only* in the case that we're doing a reflink * CoW. In all other directio scenarios we do not * allow an operation to fall back to buffered mode. */ ret = xfs_file_dio_write(iocb, from); if (ret != -ENOTBLK || (iocb->ki_flags & IOCB_ATOMIC)) return ret; } IIRC iomap_dio_rw can return ENOTBLK if pagecache invalidation fails for the region that we're trying to directio write. --D > + > /* direct I/O must be aligned to device logical sector size */ > if ((iocb->ki_pos | count) & target->bt_logical_sectormask) > return -EINVAL; > -- > 2.31.1 > >
On 30/09/2024 17:41, Darrick J. Wong wrote: > On Mon, Sep 30, 2024 at 12:54:37PM +0000, John Garry wrote: >> Validate that an atomic write adheres to length/offset rules. Currently >> we can only write a single FS block. >> >> For an IOCB with IOCB_ATOMIC set to get as far as xfs_file_dio_write(), >> FMODE_CAN_ATOMIC_WRITE will need to be set for the file; for this, >> ATOMICWRITES flags would also need to be set for the inode. >> >> Signed-off-by: John Garry <john.g.garry@oracle.com> >> --- >> fs/xfs/xfs_file.c | 7 +++++++ >> 1 file changed, 7 insertions(+) >> >> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c >> index 412b1d71b52b..fa6a44b88ecc 100644 >> --- a/fs/xfs/xfs_file.c >> +++ b/fs/xfs/xfs_file.c >> @@ -688,6 +688,13 @@ xfs_file_dio_write( >> struct xfs_buftarg *target = xfs_inode_buftarg(ip); >> size_t count = iov_iter_count(from); >> >> + if (iocb->ki_flags & IOCB_ATOMIC) { >> + if (count != ip->i_mount->m_sb.sb_blocksize) >> + return -EINVAL; >> + if (!generic_atomic_write_valid(iocb, from)) >> + return -EINVAL; >> + } > > Does xfs_file_write_iter need a catch-all so that we don't fall back to > buffered write for a directio write that returns ENOTBLK? > > if (iocb->ki_flags & IOCB_DIRECT) { > /* > * Allow a directio write to fall back to a buffered > * write *only* in the case that we're doing a reflink > * CoW. In all other directio scenarios we do not > * allow an operation to fall back to buffered mode. > */ > ret = xfs_file_dio_write(iocb, from); > if (ret != -ENOTBLK || (iocb->ki_flags & IOCB_ATOMIC)) > return ret; > } > > IIRC iomap_dio_rw can return ENOTBLK if pagecache invalidation fails for > the region that we're trying to directio write. I see where you are talking about. There is also a ENOTBLK from unaligned write for CoW, but we would not see that. But I was thinking to use a common helper to catch this, like generic_write_checks_count() [which is called on the buffered IO path]: ----8<----- diff --git a/fs/read_write.c b/fs/read_write.c index 32b476bf9be0..222f25c6439c 100644 --- a/fs/read_write.c +++ b/fs/read_write.c @@ -1774,6 +1774,10 @@ int generic_write_checks_count(struct kiocb *iocb, loff_t *count) if (!*count) return 0; + if (iocb->ki_flags & IOCB_ATOMIC && + !(iocb->ki_flags & IOCB_DIRECT)) + return -EINVAL; + if (iocb->ki_flags & IOCB_APPEND) iocb->ki_pos = i_size_read(inode); ---->8----- But we keep the IOCB_DIRECT flag for the buffered IO fallback (so no good). Another option would be: ----8<----- --- a/fs/iomap/direct-io.c +++ b/fs/iomap/direct-io.c @@ -679,7 +679,12 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter, if (ret != -EAGAIN) { trace_iomap_dio_invalidate_fail(inode, iomi.pos, iomi.len); - ret = -ENOTBLK; + if (iocb->ki_flags & IOCB_ATOMIC) { + if (ret == -ENOTBLK) + ret = -EAGAIN; + }else { + ret = -ENOTBLK; + } } goto out_free_dio; } ---->8----- I suggest that, as other FSes (like ext4) handle -ENOTBLK and would need to be changed similar to XFS. But I am not sure if changing the error code from -ENOTBLK for IOCB_ATOMIC is ok. Let me know what you think about possible alternative solutions. Thanks, John
On Tue, Oct 01, 2024 at 02:22:23PM +0100, John Garry wrote: > On 30/09/2024 17:41, Darrick J. Wong wrote: > > On Mon, Sep 30, 2024 at 12:54:37PM +0000, John Garry wrote: > > > Validate that an atomic write adheres to length/offset rules. Currently > > > we can only write a single FS block. > > > > > > For an IOCB with IOCB_ATOMIC set to get as far as xfs_file_dio_write(), > > > FMODE_CAN_ATOMIC_WRITE will need to be set for the file; for this, > > > ATOMICWRITES flags would also need to be set for the inode. > > > > > > Signed-off-by: John Garry <john.g.garry@oracle.com> > > > --- > > > fs/xfs/xfs_file.c | 7 +++++++ > > > 1 file changed, 7 insertions(+) > > > > > > diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c > > > index 412b1d71b52b..fa6a44b88ecc 100644 > > > --- a/fs/xfs/xfs_file.c > > > +++ b/fs/xfs/xfs_file.c > > > @@ -688,6 +688,13 @@ xfs_file_dio_write( > > > struct xfs_buftarg *target = xfs_inode_buftarg(ip); > > > size_t count = iov_iter_count(from); > > > + if (iocb->ki_flags & IOCB_ATOMIC) { > > > + if (count != ip->i_mount->m_sb.sb_blocksize) > > > + return -EINVAL; > > > + if (!generic_atomic_write_valid(iocb, from)) > > > + return -EINVAL; > > > + } > > > > Does xfs_file_write_iter need a catch-all so that we don't fall back to > > buffered write for a directio write that returns ENOTBLK? > > > > if (iocb->ki_flags & IOCB_DIRECT) { > > /* > > * Allow a directio write to fall back to a buffered > > * write *only* in the case that we're doing a reflink > > * CoW. In all other directio scenarios we do not > > * allow an operation to fall back to buffered mode. > > */ > > ret = xfs_file_dio_write(iocb, from); > > if (ret != -ENOTBLK || (iocb->ki_flags & IOCB_ATOMIC)) > > return ret; > > } > > > > IIRC iomap_dio_rw can return ENOTBLK if pagecache invalidation fails for > > the region that we're trying to directio write. > > I see where you are talking about. There is also a ENOTBLK from unaligned > write for CoW, but we would not see that. > > But I was thinking to use a common helper to catch this, like > generic_write_checks_count() [which is called on the buffered IO path]: > > ----8<----- > > diff --git a/fs/read_write.c b/fs/read_write.c > index 32b476bf9be0..222f25c6439c 100644 > --- a/fs/read_write.c > +++ b/fs/read_write.c > @@ -1774,6 +1774,10 @@ int generic_write_checks_count(struct kiocb *iocb, > loff_t *count) > if (!*count) > return 0; > > + if (iocb->ki_flags & IOCB_ATOMIC && > + !(iocb->ki_flags & IOCB_DIRECT)) > + return -EINVAL; > + > if (iocb->ki_flags & IOCB_APPEND) > iocb->ki_pos = i_size_read(inode); > > ---->8----- > > But we keep the IOCB_DIRECT flag for the buffered IO fallback (so no good). > > Another option would be: > > ----8<----- > > --- a/fs/iomap/direct-io.c > +++ b/fs/iomap/direct-io.c > @@ -679,7 +679,12 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter > *iter, > if (ret != -EAGAIN) { > trace_iomap_dio_invalidate_fail(inode, iomi.pos, > iomi.len); > - ret = -ENOTBLK; > + if (iocb->ki_flags & IOCB_ATOMIC) { > + if (ret == -ENOTBLK) > + ret = -EAGAIN; I don't follow the logic here -- all the error codes except for EAGAIN are squashed into ENOTBLK, so why would we let them through for an atomic write? if (ret != -EAGAIN) { trace_iomap_dio_invalidate_fail(inode, iomi.pos, iomi.len); if (iocb->ki_flags & IOCB_ATOMIC) { /* * folio invalidation failed, maybe this is * transient, unlock and see if the caller * tries again */ return -EAGAIN; } else { /* fall back to buffered write */ return -ENOTBLK; } } --D > + }else { > + ret = -ENOTBLK; > + } > } > goto out_free_dio; > } > ---->8----- > > I suggest that, as other FSes (like ext4) handle -ENOTBLK and would need to > be changed similar to XFS. But I am not sure if changing the error code from > -ENOTBLK for IOCB_ATOMIC is ok. > > Let me know what you think about possible alternative solutions. > > Thanks, > John >
On 01/10/2024 15:48, Darrick J. Wong wrote: >> --- a/fs/iomap/direct-io.c >> +++ b/fs/iomap/direct-io.c >> @@ -679,7 +679,12 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter >> *iter, >> if (ret != -EAGAIN) { >> trace_iomap_dio_invalidate_fail(inode, iomi.pos, >> iomi.len); >> - ret = -ENOTBLK; >> + if (iocb->ki_flags & IOCB_ATOMIC) { >> + if (ret == -ENOTBLK) >> + ret = -EAGAIN; > I don't follow the logic here -- all the error codes except for EAGAIN > are squashed into ENOTBLK, so why would we let them through for an > atomic write? Right, the errors apart from EAGAIN are normally squashed to ENOTBLK; but I thought that since we would not do this for IOCB_ATOMIC, then just return the actual error from kiocb_invalidate_pages() - apart from ENOTBLK, which has this special treatment. But I can always just return EAGAIN for IOCB_ATOMIC when kiocb_invalidate_pages() errors, as you suggest below. > > if (ret != -EAGAIN) { > trace_iomap_dio_invalidate_fail(inode, iomi.pos, > iomi.len); > > if (iocb->ki_flags & IOCB_ATOMIC) { > /* > * folio invalidation failed, maybe this is > * transient, unlock and see if the caller > * tries again > */ > return -EAGAIN; > } else { > /* fall back to buffered write */ > return -ENOTBLK; > } > } Cheers, John
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c index 412b1d71b52b..fa6a44b88ecc 100644 --- a/fs/xfs/xfs_file.c +++ b/fs/xfs/xfs_file.c @@ -688,6 +688,13 @@ xfs_file_dio_write( struct xfs_buftarg *target = xfs_inode_buftarg(ip); size_t count = iov_iter_count(from); + if (iocb->ki_flags & IOCB_ATOMIC) { + if (count != ip->i_mount->m_sb.sb_blocksize) + return -EINVAL; + if (!generic_atomic_write_valid(iocb, from)) + return -EINVAL; + } + /* direct I/O must be aligned to device logical sector size */ if ((iocb->ki_pos | count) & target->bt_logical_sectormask) return -EINVAL;
Validate that an atomic write adheres to length/offset rules. Currently we can only write a single FS block. For an IOCB with IOCB_ATOMIC set to get as far as xfs_file_dio_write(), FMODE_CAN_ATOMIC_WRITE will need to be set for the file; for this, ATOMICWRITES flags would also need to be set for the inode. Signed-off-by: John Garry <john.g.garry@oracle.com> --- fs/xfs/xfs_file.c | 7 +++++++ 1 file changed, 7 insertions(+)