| Message ID | 75a6ead09a10e362526a849af482510a0090f82a.1567978633.git.mbobrowski@mbobrowski.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | ext4: port direct IO to iomap infrastructure | expand |
On 9/9/19 4:48 AM, Matthew Bobrowski wrote: > This patch introduces a new direct IO read path that makes use of the > iomap infrastructure. > > The new function ext4_dio_read_iter() is responsible for calling into > the iomap infrastructure via iomap_dio_rw(). If the inode in question > does not pass preliminary checks in ext4_dio_checks(), then we simply > fallback to buffered IO and take that path to fulfil the request. It's > imperative that we drop the IOCB_DIRECT flag from iocb->ki_flags in > order to prevent generic_file_read_iter() from trying to take the > direct IO code path again. > > Signed-off-by: Matthew Bobrowski <mbobrowski@mbobrowski.org> Looks good to me. Reviewed-by: Ritesh Harjani <riteshh@linux.ibm.com> > --- > fs/ext4/file.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++---- > 1 file changed, 54 insertions(+), 4 deletions(-) > > diff --git a/fs/ext4/file.c b/fs/ext4/file.c > index 70b0438dbc94..e52e3928dc25 100644 > --- a/fs/ext4/file.c > +++ b/fs/ext4/file.c > @@ -34,6 +34,53 @@ > #include "xattr.h" > #include "acl.h" > > +static bool ext4_dio_checks(struct inode *inode) > +{ > +#if IS_ENABLED(CONFIG_FS_ENCRYPTION) > + if (IS_ENCRYPTED(inode)) > + return false; > +#endif > + if (ext4_should_journal_data(inode)) > + return false; > + if (ext4_has_inline_data(inode)) > + return false; > + return true; > +} > + > +static ssize_t ext4_dio_read_iter(struct kiocb *iocb, struct iov_iter *to) > +{ > + ssize_t ret; > + struct inode *inode = file_inode(iocb->ki_filp); > + > + /* > + * Get exclusion from truncate and other inode operations. > + */ > + if (!inode_trylock_shared(inode)) { > + if (iocb->ki_flags & IOCB_NOWAIT) > + return -EAGAIN; > + inode_lock_shared(inode); > + } > + > + if (!ext4_dio_checks(inode)) { > + inode_unlock_shared(inode); > + /* > + * Fallback to buffered IO if the operation being > + * performed on the inode is not supported by direct > + * IO. The IOCB_DIRECT flag flags needs to be cleared > + * here to ensure that the direct IO code path within > + * generic_file_read_iter() is not taken again. > + */ > + iocb->ki_flags &= ~IOCB_DIRECT; > + return generic_file_read_iter(iocb, to); > + } > + > + ret = iomap_dio_rw(iocb, to, &ext4_iomap_ops, NULL); > + inode_unlock_shared(inode); > + > + file_accessed(iocb->ki_filp); > + return ret; > +} > + > #ifdef CONFIG_FS_DAX > static ssize_t ext4_dax_read_iter(struct kiocb *iocb, struct iov_iter *to) > { > @@ -64,16 +111,19 @@ static ssize_t ext4_dax_read_iter(struct kiocb *iocb, struct iov_iter *to) > > static ssize_t ext4_file_read_iter(struct kiocb *iocb, struct iov_iter *to) > { > - if (unlikely(ext4_forced_shutdown(EXT4_SB(file_inode(iocb->ki_filp)->i_sb)))) > + struct inode *inode = file_inode(iocb->ki_filp); > + > + if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb)))) > return -EIO; > > if (!iov_iter_count(to)) > return 0; /* skip atime */ > > -#ifdef CONFIG_FS_DAX > - if (IS_DAX(file_inode(iocb->ki_filp))) > + if (IS_DAX(inode)) > return ext4_dax_read_iter(iocb, to); > -#endif > + > + if (iocb->ki_flags & IOCB_DIRECT) > + return ext4_dio_read_iter(iocb, to); > return generic_file_read_iter(iocb, to); > } >
diff --git a/fs/ext4/file.c b/fs/ext4/file.c index 70b0438dbc94..e52e3928dc25 100644 --- a/fs/ext4/file.c +++ b/fs/ext4/file.c @@ -34,6 +34,53 @@ #include "xattr.h" #include "acl.h" +static bool ext4_dio_checks(struct inode *inode) +{ +#if IS_ENABLED(CONFIG_FS_ENCRYPTION) + if (IS_ENCRYPTED(inode)) + return false; +#endif + if (ext4_should_journal_data(inode)) + return false; + if (ext4_has_inline_data(inode)) + return false; + return true; +} + +static ssize_t ext4_dio_read_iter(struct kiocb *iocb, struct iov_iter *to) +{ + ssize_t ret; + struct inode *inode = file_inode(iocb->ki_filp); + + /* + * Get exclusion from truncate and other inode operations. + */ + if (!inode_trylock_shared(inode)) { + if (iocb->ki_flags & IOCB_NOWAIT) + return -EAGAIN; + inode_lock_shared(inode); + } + + if (!ext4_dio_checks(inode)) { + inode_unlock_shared(inode); + /* + * Fallback to buffered IO if the operation being + * performed on the inode is not supported by direct + * IO. The IOCB_DIRECT flag flags needs to be cleared + * here to ensure that the direct IO code path within + * generic_file_read_iter() is not taken again. + */ + iocb->ki_flags &= ~IOCB_DIRECT; + return generic_file_read_iter(iocb, to); + } + + ret = iomap_dio_rw(iocb, to, &ext4_iomap_ops, NULL); + inode_unlock_shared(inode); + + file_accessed(iocb->ki_filp); + return ret; +} + #ifdef CONFIG_FS_DAX static ssize_t ext4_dax_read_iter(struct kiocb *iocb, struct iov_iter *to) { @@ -64,16 +111,19 @@ static ssize_t ext4_dax_read_iter(struct kiocb *iocb, struct iov_iter *to) static ssize_t ext4_file_read_iter(struct kiocb *iocb, struct iov_iter *to) { - if (unlikely(ext4_forced_shutdown(EXT4_SB(file_inode(iocb->ki_filp)->i_sb)))) + struct inode *inode = file_inode(iocb->ki_filp); + + if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb)))) return -EIO; if (!iov_iter_count(to)) return 0; /* skip atime */ -#ifdef CONFIG_FS_DAX - if (IS_DAX(file_inode(iocb->ki_filp))) + if (IS_DAX(inode)) return ext4_dax_read_iter(iocb, to); -#endif + + if (iocb->ki_flags & IOCB_DIRECT) + return ext4_dio_read_iter(iocb, to); return generic_file_read_iter(iocb, to); }
This patch introduces a new direct IO read path that makes use of the iomap infrastructure. The new function ext4_dio_read_iter() is responsible for calling into the iomap infrastructure via iomap_dio_rw(). If the inode in question does not pass preliminary checks in ext4_dio_checks(), then we simply fallback to buffered IO and take that path to fulfil the request. It's imperative that we drop the IOCB_DIRECT flag from iocb->ki_flags in order to prevent generic_file_read_iter() from trying to take the direct IO code path again. Signed-off-by: Matthew Bobrowski <mbobrowski@mbobrowski.org> --- fs/ext4/file.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 54 insertions(+), 4 deletions(-)