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linux-kernel@vger.kernel.org, linux_oss@crudebyte.com Date: Mon, 29 Jan 2024 07:43:35 -0500 In-Reply-To: <20240129094924.1221977-3-dhowells@redhat.com> References: <20240129094924.1221977-1-dhowells@redhat.com> <20240129094924.1221977-3-dhowells@redhat.com> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; 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 kZWuOsJdJQdmwlWC5L5ln9xgfr/4mOY38B0U= Content-Type: text/plain; charset="ISO-8859-15" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.50.3 (3.50.3-1.fc39) Precedence: bulk X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Mon, 2024-01-29 at 09:49 +0000, David Howells wrote: > Fix netfs_unbuffered_write_iter() to return immediately if > generic_write_checks() returns 0, indicating there's nothing to write. > Note that netfs_file_write_iter() already does this. >=20 > Also, whilst we're at it, put in checks for the size being zero before we > even take the locks. Note that generic_write_checks() can still reduce t= he > size to zero, so we still need that check. >=20 > Without this, a warning similar to the following is logged to dmesg: >=20 > netfs: Zero-sized write [R=3D1b6da] >=20 > and the syscall fails with EIO, e.g.: >=20 > /sbin/ldconfig.real: Writing of cache extension data failed: Input/outpu= t error >=20 > This can be reproduced on 9p by: >=20 > xfs_io -f -c 'pwrite 0 0' /xfstest.test/foo >=20 > Fixes: 153a9961b551 ("netfs: Implement unbuffered/DIO write support") > Reported-by: Eric Van Hensbergen > Link: https://lore.kernel.org/r/ZbQUU6QKmIftKsmo@FV7GG9FTHL/ > Signed-off-by: David Howells > cc: Dominique Martinet > cc: Jeff Layton > cc: v9fs@lists.linux.dev > cc: linux_oss@crudebyte.com > cc: netfs@lists.linux.dev > cc: linux-fsdevel@vger.kernel.org > --- > fs/netfs/buffered_write.c | 3 +++ > fs/netfs/direct_write.c | 5 ++++- > 2 files changed, 7 insertions(+), 1 deletion(-) >=20 > diff --git a/fs/netfs/buffered_write.c b/fs/netfs/buffered_write.c > index a3059b3168fd..9a0d32e4b422 100644 > --- a/fs/netfs/buffered_write.c > +++ b/fs/netfs/buffered_write.c > @@ -477,6 +477,9 @@ ssize_t netfs_file_write_iter(struct kiocb *iocb, str= uct iov_iter *from) > =20 > _enter("%llx,%zx,%llx", iocb->ki_pos, iov_iter_count(from), i_size_read= (inode)); > =20 > + if (!iov_iter_count(from)) > + return 0; > + > if ((iocb->ki_flags & IOCB_DIRECT) || > test_bit(NETFS_ICTX_UNBUFFERED, &ictx->flags)) > return netfs_unbuffered_write_iter(iocb, from); > diff --git a/fs/netfs/direct_write.c b/fs/netfs/direct_write.c > index 60a40d293c87..bee047e20f5d 100644 > --- a/fs/netfs/direct_write.c > +++ b/fs/netfs/direct_write.c > @@ -139,6 +139,9 @@ ssize_t netfs_unbuffered_write_iter(struct kiocb *ioc= b, struct iov_iter *from) > =20 > _enter("%llx,%zx,%llx", iocb->ki_pos, iov_iter_count(from), i_size_read= (inode)); > =20 > + if (!iov_iter_count(from)) > + return 0; > + > trace_netfs_write_iter(iocb, from); > netfs_stat(&netfs_n_rh_dio_write); > =20 > @@ -146,7 +149,7 @@ ssize_t netfs_unbuffered_write_iter(struct kiocb *ioc= b, struct iov_iter *from) > if (ret < 0) > return ret; > ret =3D generic_write_checks(iocb, from); > - if (ret < 0) > + if (ret <=3D 0) > goto out; > ret =3D file_remove_privs(file); > if (ret < 0) >=20 Reviewed-by: Jeff Layton