| Message ID | 1ba5bfccccbf4ff792f178268badde056797d0c4.1712126039.git.sweettea-kernel@dorminy.me (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | fiemap extension for more physical information | expand |
On Wed, Apr 03, 2024 at 03:22:42AM -0400, Sweet Tea Dorminy wrote: > Some filesystems support compressed extents which have a larger logical > size than physical, and for those filesystems, it can be useful for > userspace to know how much space those extents actually use. For > instance, the compsize [1] tool for btrfs currently uses btrfs-internal, > root-only ioctl to find the actual disk space used by a file; it would > be better and more useful for this information to require fewer > privileges and to be usable on more filesystems. Therefore, use one of > the padding u64s in the fiemap extent structure to return the actual > physical length; and, for now, return this as equal to the logical > length. > > [1] https://github.com/kilobyte/compsize > > Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me> > --- > Documentation/filesystems/fiemap.rst | 28 +++++++++++++++++------- > fs/ioctl.c | 3 ++- > include/uapi/linux/fiemap.h | 32 ++++++++++++++++++++++------ > 3 files changed, 47 insertions(+), 16 deletions(-) > ... > diff --git a/fs/ioctl.c b/fs/ioctl.c > index 661b46125669..8afd32e1a27a 100644 > --- a/fs/ioctl.c > +++ b/fs/ioctl.c > @@ -138,7 +138,8 @@ int fiemap_fill_next_extent(struct fiemap_extent_info *fieinfo, u64 logical, > memset(&extent, 0, sizeof(extent)); > extent.fe_logical = logical; > extent.fe_physical = phys; > - extent.fe_length = len; > + extent.fe_logical_length = len; > + extent.fe_physical_length = len; Nit: Why start this field out as len if the next patch adds the param and defaults to zero? Not that it matters that much due to the next patch (which seems logical), but wouldn't it make more sense to set this to 0 from the start? Brian > extent.fe_flags = flags; > > dest += fieinfo->fi_extents_mapped; > diff --git a/include/uapi/linux/fiemap.h b/include/uapi/linux/fiemap.h > index 24ca0c00cae3..3079159b8e94 100644 > --- a/include/uapi/linux/fiemap.h > +++ b/include/uapi/linux/fiemap.h > @@ -14,14 +14,30 @@ > > #include <linux/types.h> > > +/* > + * For backward compatibility, where the member of the struct was called > + * fe_length instead of fe_logical_length. > + */ > +#define fe_length fe_logical_length > + > struct fiemap_extent { > - __u64 fe_logical; /* logical offset in bytes for the start of > - * the extent from the beginning of the file */ > - __u64 fe_physical; /* physical offset in bytes for the start > - * of the extent from the beginning of the disk */ > - __u64 fe_length; /* length in bytes for this extent */ > - __u64 fe_reserved64[2]; > - __u32 fe_flags; /* FIEMAP_EXTENT_* flags for this extent */ > + /* > + * logical offset in bytes for the start of > + * the extent from the beginning of the file > + */ > + __u64 fe_logical; > + /* > + * physical offset in bytes for the start > + * of the extent from the beginning of the disk > + */ > + __u64 fe_physical; > + /* logical length in bytes for this extent */ > + __u64 fe_logical_length; > + /* physical length in bytes for this extent */ > + __u64 fe_physical_length; > + __u64 fe_reserved64[1]; > + /* FIEMAP_EXTENT_* flags for this extent */ > + __u32 fe_flags; > __u32 fe_reserved[3]; > }; > > @@ -66,5 +82,7 @@ struct fiemap { > * merged for efficiency. */ > #define FIEMAP_EXTENT_SHARED 0x00002000 /* Space shared with other > * files. */ > +#define FIEMAP_EXTENT_HAS_PHYS_LEN 0x00004000 /* Physical length is valid > + * and set by FS. */ > > #endif /* _UAPI_LINUX_FIEMAP_H */ > -- > 2.43.0 > >
On Apr 3, 2024, at 1:22 AM, Sweet Tea Dorminy <sweettea-kernel@dorminy.me> wrote: > > Some filesystems support compressed extents which have a larger logical > size than physical, and for those filesystems, it can be useful for > userspace to know how much space those extents actually use. For > instance, the compsize [1] tool for btrfs currently uses btrfs-internal, > root-only ioctl to find the actual disk space used by a file; it would > be better and more useful for this information to require fewer > privileges and to be usable on more filesystems. Therefore, use one of > the padding u64s in the fiemap extent structure to return the actual > physical length; and, for now, return this as equal to the logical > length. > > [1] https://github.com/kilobyte/compsize > > Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me> > --- > Documentation/filesystems/fiemap.rst | 28 +++++++++++++++++------- > fs/ioctl.c | 3 ++- > include/uapi/linux/fiemap.h | 32 ++++++++++++++++++++++------ > 3 files changed, 47 insertions(+), 16 deletions(-) > > diff --git a/Documentation/filesystems/fiemap.rst b/Documentation/filesystems/fiemap.rst > index 93fc96f760aa..c2bfa107c8d7 100644 > --- a/Documentation/filesystems/fiemap.rst > +++ b/Documentation/filesystems/fiemap.rst > @@ -80,14 +80,24 @@ Each extent is described by a single fiemap_extent structure as > returned in fm_extents:: > > struct fiemap_extent { > - __u64 fe_logical; /* logical offset in bytes for the start of > - * the extent */ > - __u64 fe_physical; /* physical offset in bytes for the start > - * of the extent */ > - __u64 fe_length; /* length in bytes for the extent */ > - __u64 fe_reserved64[2]; > - __u32 fe_flags; /* FIEMAP_EXTENT_* flags for this extent */ > - __u32 fe_reserved[3]; > + /* > + * logical offset in bytes for the start of > + * the extent from the beginning of the file > + */ > + __u64 fe_logical; > + /* > + * physical offset in bytes for the start > + * of the extent from the beginning of the disk > + */ > + __u64 fe_physical; > + /* logical length in bytes for this extent */ > + __u64 fe_logical_length; > + /* physical length in bytes for this extent */ > + __u64 fe_physical_length; > + __u64 fe_reserved64[1]; > + /* FIEMAP_EXTENT_* flags for this extent */ > + __u32 fe_flags; > + __u32 fe_reserved[3]; > }; > > All offsets and lengths are in bytes and mirror those on disk. It is valid > @@ -175,6 +185,8 @@ FIEMAP_EXTENT_MERGED > userspace would be highly inefficient, the kernel will try to merge most > adjacent blocks into 'extents'. > > +FIEMAP_EXTENT_HAS_PHYS_LEN > + This will be set if the file system populated the physical length field. > > VFS -> File System Implementation > --------------------------------- > diff --git a/fs/ioctl.c b/fs/ioctl.c > index 661b46125669..8afd32e1a27a 100644 > --- a/fs/ioctl.c > +++ b/fs/ioctl.c > @@ -138,7 +138,8 @@ int fiemap_fill_next_extent(struct fiemap_extent_info *fieinfo, u64 logical, > memset(&extent, 0, sizeof(extent)); > extent.fe_logical = logical; > extent.fe_physical = phys; > - extent.fe_length = len; > + extent.fe_logical_length = len; > + extent.fe_physical_length = len; I think Jan mentioned this already, and I agree, that fe_physical_length should be left = 0 initially, and be set only when FIEMAP_EXTENT_HAS_PHYS_LEN is set (either explicitly passed from the filesystem, OR possibly set internally by the common fiemap code along with FIEMAP_EXTENT_HAS_PHYS_LEN if the filesystem didn't set this flag itself. I don't think it makes sense to set fe_physical length in this patch before FIEMAP_EXTENT_HAS_PHYS_LEN is set, nor in the later filesystem-specific patches that are passing "0" for the physical length instead of "len". Cheers, Andreas > extent.fe_flags = flags; > > dest += fieinfo->fi_extents_mapped; > diff --git a/include/uapi/linux/fiemap.h b/include/uapi/linux/fiemap.h > index 24ca0c00cae3..3079159b8e94 100644 > --- a/include/uapi/linux/fiemap.h > +++ b/include/uapi/linux/fiemap.h > @@ -14,14 +14,30 @@ > > #include <linux/types.h> > > +/* > + * For backward compatibility, where the member of the struct was called > + * fe_length instead of fe_logical_length. > + */ > +#define fe_length fe_logical_length > + > struct fiemap_extent { > - __u64 fe_logical; /* logical offset in bytes for the start of > - * the extent from the beginning of the file */ > - __u64 fe_physical; /* physical offset in bytes for the start > - * of the extent from the beginning of the disk */ > - __u64 fe_length; /* length in bytes for this extent */ > - __u64 fe_reserved64[2]; > - __u32 fe_flags; /* FIEMAP_EXTENT_* flags for this extent */ > + /* > + * logical offset in bytes for the start of > + * the extent from the beginning of the file > + */ > + __u64 fe_logical; > + /* > + * physical offset in bytes for the start > + * of the extent from the beginning of the disk > + */ > + __u64 fe_physical; > + /* logical length in bytes for this extent */ > + __u64 fe_logical_length; > + /* physical length in bytes for this extent */ > + __u64 fe_physical_length; > + __u64 fe_reserved64[1]; > + /* FIEMAP_EXTENT_* flags for this extent */ > + __u32 fe_flags; > __u32 fe_reserved[3]; > }; > > @@ -66,5 +82,7 @@ struct fiemap { > * merged for efficiency. */ > #define FIEMAP_EXTENT_SHARED 0x00002000 /* Space shared with other > * files. */ > +#define FIEMAP_EXTENT_HAS_PHYS_LEN 0x00004000 /* Physical length is valid > + * and set by FS. */ > > #endif /* _UAPI_LINUX_FIEMAP_H */ > -- > 2.43.0 > > Cheers, Andreas
On Wed, Apr 03, 2024 at 03:22:42AM -0400, Sweet Tea Dorminy wrote: > Some filesystems support compressed extents which have a larger logical > size than physical, and for those filesystems, it can be useful for > userspace to know how much space those extents actually use. For > instance, the compsize [1] tool for btrfs currently uses btrfs-internal, > root-only ioctl to find the actual disk space used by a file; it would > be better and more useful for this information to require fewer > privileges and to be usable on more filesystems. Therefore, use one of > the padding u64s in the fiemap extent structure to return the actual > physical length; and, for now, return this as equal to the logical > length. > > [1] https://github.com/kilobyte/compsize > > Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me> > --- > Documentation/filesystems/fiemap.rst | 28 +++++++++++++++++------- > fs/ioctl.c | 3 ++- > include/uapi/linux/fiemap.h | 32 ++++++++++++++++++++++------ > 3 files changed, 47 insertions(+), 16 deletions(-) > > diff --git a/Documentation/filesystems/fiemap.rst b/Documentation/filesystems/fiemap.rst > index 93fc96f760aa..c2bfa107c8d7 100644 > --- a/Documentation/filesystems/fiemap.rst > +++ b/Documentation/filesystems/fiemap.rst > @@ -80,14 +80,24 @@ Each extent is described by a single fiemap_extent structure as > returned in fm_extents:: > > struct fiemap_extent { > - __u64 fe_logical; /* logical offset in bytes for the start of > - * the extent */ > - __u64 fe_physical; /* physical offset in bytes for the start > - * of the extent */ > - __u64 fe_length; /* length in bytes for the extent */ > - __u64 fe_reserved64[2]; > - __u32 fe_flags; /* FIEMAP_EXTENT_* flags for this extent */ > - __u32 fe_reserved[3]; > + /* > + * logical offset in bytes for the start of > + * the extent from the beginning of the file > + */ > + __u64 fe_logical; > + /* > + * physical offset in bytes for the start > + * of the extent from the beginning of the disk > + */ > + __u64 fe_physical; > + /* logical length in bytes for this extent */ > + __u64 fe_logical_length; > + /* physical length in bytes for this extent */ > + __u64 fe_physical_length; > + __u64 fe_reserved64[1]; > + /* FIEMAP_EXTENT_* flags for this extent */ > + __u32 fe_flags; > + __u32 fe_reserved[3]; > }; > > All offsets and lengths are in bytes and mirror those on disk. It is valid > @@ -175,6 +185,8 @@ FIEMAP_EXTENT_MERGED > userspace would be highly inefficient, the kernel will try to merge most > adjacent blocks into 'extents'. > > +FIEMAP_EXTENT_HAS_PHYS_LEN > + This will be set if the file system populated the physical length field. Just out of curiosity, should filesystems set this flag and fe_physical_length if fe_physical_length == fe_logical_length? Or just leave both blank? > VFS -> File System Implementation > --------------------------------- > diff --git a/fs/ioctl.c b/fs/ioctl.c > index 661b46125669..8afd32e1a27a 100644 > --- a/fs/ioctl.c > +++ b/fs/ioctl.c > @@ -138,7 +138,8 @@ int fiemap_fill_next_extent(struct fiemap_extent_info *fieinfo, u64 logical, > memset(&extent, 0, sizeof(extent)); > extent.fe_logical = logical; > extent.fe_physical = phys; > - extent.fe_length = len; > + extent.fe_logical_length = len; > + extent.fe_physical_length = len; > extent.fe_flags = flags; > > dest += fieinfo->fi_extents_mapped; > diff --git a/include/uapi/linux/fiemap.h b/include/uapi/linux/fiemap.h > index 24ca0c00cae3..3079159b8e94 100644 > --- a/include/uapi/linux/fiemap.h > +++ b/include/uapi/linux/fiemap.h > @@ -14,14 +14,30 @@ > > #include <linux/types.h> > > +/* > + * For backward compatibility, where the member of the struct was called > + * fe_length instead of fe_logical_length. > + */ > +#define fe_length fe_logical_length This #define has global scope; are you sure this isn't going to cause a weird build problem downstream with some program that declares an unrelated fe_length symbol? > + > struct fiemap_extent { > - __u64 fe_logical; /* logical offset in bytes for the start of > - * the extent from the beginning of the file */ > - __u64 fe_physical; /* physical offset in bytes for the start > - * of the extent from the beginning of the disk */ > - __u64 fe_length; /* length in bytes for this extent */ > - __u64 fe_reserved64[2]; > - __u32 fe_flags; /* FIEMAP_EXTENT_* flags for this extent */ > + /* > + * logical offset in bytes for the start of > + * the extent from the beginning of the file > + */ > + __u64 fe_logical; > + /* > + * physical offset in bytes for the start > + * of the extent from the beginning of the disk > + */ > + __u64 fe_physical; > + /* logical length in bytes for this extent */ > + __u64 fe_logical_length; Or why not just leave the field name the same since the "logical length in bytes" comment is present both here in the header and again in the documentation? --D > + /* physical length in bytes for this extent */ > + __u64 fe_physical_length; > + __u64 fe_reserved64[1]; > + /* FIEMAP_EXTENT_* flags for this extent */ > + __u32 fe_flags; > __u32 fe_reserved[3]; > }; > > @@ -66,5 +82,7 @@ struct fiemap { > * merged for efficiency. */ > #define FIEMAP_EXTENT_SHARED 0x00002000 /* Space shared with other > * files. */ > +#define FIEMAP_EXTENT_HAS_PHYS_LEN 0x00004000 /* Physical length is valid > + * and set by FS. */ > > #endif /* _UAPI_LINUX_FIEMAP_H */ > -- > 2.43.0 > >
On Apr 9, 2024, at 10:22 AM, Darrick J. Wong <djwong@kernel.org> wrote: > > On Wed, Apr 03, 2024 at 03:22:42AM -0400, Sweet Tea Dorminy wrote: >> Some filesystems support compressed extents which have a larger logical >> size than physical, and for those filesystems, it can be useful for >> userspace to know how much space those extents actually use. For >> instance, the compsize [1] tool for btrfs currently uses btrfs-internal, >> root-only ioctl to find the actual disk space used by a file; it would >> be better and more useful for this information to require fewer >> privileges and to be usable on more filesystems. Therefore, use one of >> the padding u64s in the fiemap extent structure to return the actual >> physical length; and, for now, return this as equal to the logical >> length. >> >> [1] https://github.com/kilobyte/compsize >> >> Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me> >> --- >> Documentation/filesystems/fiemap.rst | 28 +++++++++++++++++------- >> fs/ioctl.c | 3 ++- >> include/uapi/linux/fiemap.h | 32 ++++++++++++++++++++++------ >> 3 files changed, 47 insertions(+), 16 deletions(-) >> >> diff --git a/Documentation/filesystems/fiemap.rst b/Documentation/filesystems/fiemap.rst >> index 93fc96f760aa..c2bfa107c8d7 100644 >> --- a/Documentation/filesystems/fiemap.rst >> +++ b/Documentation/filesystems/fiemap.rst >> @@ -80,14 +80,24 @@ Each extent is described by a single fiemap_extent structure as >> returned in fm_extents:: >> >> struct fiemap_extent { >> - __u64 fe_logical; /* logical offset in bytes for the start of >> - * the extent */ >> - __u64 fe_physical; /* physical offset in bytes for the start >> - * of the extent */ >> - __u64 fe_length; /* length in bytes for the extent */ >> - __u64 fe_reserved64[2]; >> - __u32 fe_flags; /* FIEMAP_EXTENT_* flags for this extent */ >> - __u32 fe_reserved[3]; >> + /* >> + * logical offset in bytes for the start of >> + * the extent from the beginning of the file >> + */ >> + __u64 fe_logical; >> + /* >> + * physical offset in bytes for the start >> + * of the extent from the beginning of the disk >> + */ >> + __u64 fe_physical; >> + /* logical length in bytes for this extent */ >> + __u64 fe_logical_length; >> + /* physical length in bytes for this extent */ >> + __u64 fe_physical_length; >> + __u64 fe_reserved64[1]; >> + /* FIEMAP_EXTENT_* flags for this extent */ >> + __u32 fe_flags; >> + __u32 fe_reserved[3]; >> }; >> >> All offsets and lengths are in bytes and mirror those on disk. It is valid >> @@ -175,6 +185,8 @@ FIEMAP_EXTENT_MERGED >> userspace would be highly inefficient, the kernel will try to merge most >> adjacent blocks into 'extents'. >> >> +FIEMAP_EXTENT_HAS_PHYS_LEN >> + This will be set if the file system populated the physical length field. > > Just out of curiosity, should filesystems set this flag and > fe_physical_length if fe_physical_length == fe_logical_length? > Or just leave both blank? In the original thread, Dave thought it would be better to always set fe_physical_length and the flag, so that userspace applications which do not properly check the flag will not be confused/broken by differences in filesystem behavior in the future when this is in use. https://patchwork.ozlabs.org/project/linux-ext4/patch/4f8d5dc5b51a43efaf16c39398c23a6276e40a30.1386778303.git.dsterba@suse.cz/ > >> VFS -> File System Implementation >> --------------------------------- >> diff --git a/fs/ioctl.c b/fs/ioctl.c >> index 661b46125669..8afd32e1a27a 100644 >> --- a/fs/ioctl.c >> +++ b/fs/ioctl.c >> @@ -138,7 +138,8 @@ int fiemap_fill_next_extent(struct fiemap_extent_info *fieinfo, u64 logical, >> memset(&extent, 0, sizeof(extent)); >> extent.fe_logical = logical; >> extent.fe_physical = phys; >> - extent.fe_length = len; >> + extent.fe_logical_length = len; >> + extent.fe_physical_length = len; >> extent.fe_flags = flags; >> >> dest += fieinfo->fi_extents_mapped; >> diff --git a/include/uapi/linux/fiemap.h b/include/uapi/linux/fiemap.h >> index 24ca0c00cae3..3079159b8e94 100644 >> --- a/include/uapi/linux/fiemap.h >> +++ b/include/uapi/linux/fiemap.h >> @@ -14,14 +14,30 @@ >> >> #include <linux/types.h> >> >> +/* >> + * For backward compatibility, where the member of the struct was called >> + * fe_length instead of fe_logical_length. >> + */ >> +#define fe_length fe_logical_length > > This #define has global scope; are you sure this isn't going to cause a > weird build problem downstream with some program that declares an > unrelated fe_length symbol? I guess it's possible. I'm not dead set on this part of the change. I thought it was cleaner to separate the two in the struct, but I can see the argument that a UAPI field struct should not change names. It would be possible to have: #define fe_logical_length fe_length which would have much less chance of namespace collisions I think. New applications can start to use this for some years, before making a permanent switch, but again not something I'm stuck on... Cheers, Andreas >> + >> struct fiemap_extent { >> - __u64 fe_logical; /* logical offset in bytes for the start of >> - * the extent from the beginning of the file */ >> - __u64 fe_physical; /* physical offset in bytes for the start >> - * of the extent from the beginning of the disk */ >> - __u64 fe_length; /* length in bytes for this extent */ >> - __u64 fe_reserved64[2]; >> - __u32 fe_flags; /* FIEMAP_EXTENT_* flags for this extent */ >> + /* >> + * logical offset in bytes for the start of >> + * the extent from the beginning of the file >> + */ >> + __u64 fe_logical; >> + /* >> + * physical offset in bytes for the start >> + * of the extent from the beginning of the disk >> + */ >> + __u64 fe_physical; >> + /* logical length in bytes for this extent */ >> + __u64 fe_logical_length; > > Or why not just leave the field name the same since the "logical length > in bytes" comment is present both here in the header and again in the > documentation? > > --D > >> + /* physical length in bytes for this extent */ >> + __u64 fe_physical_length; >> + __u64 fe_reserved64[1]; >> + /* FIEMAP_EXTENT_* flags for this extent */ >> + __u32 fe_flags; >> __u32 fe_reserved[3]; >> }; >> >> @@ -66,5 +82,7 @@ struct fiemap { >> * merged for efficiency. */ >> #define FIEMAP_EXTENT_SHARED 0x00002000 /* Space shared with other >> * files. */ >> +#define FIEMAP_EXTENT_HAS_PHYS_LEN 0x00004000 /* Physical length is valid >> + * and set by FS. */ >> >> #endif /* _UAPI_LINUX_FIEMAP_H */ >> -- >> 2.43.0 >> >> > Cheers, Andreas
diff --git a/Documentation/filesystems/fiemap.rst b/Documentation/filesystems/fiemap.rst index 93fc96f760aa..c2bfa107c8d7 100644 --- a/Documentation/filesystems/fiemap.rst +++ b/Documentation/filesystems/fiemap.rst @@ -80,14 +80,24 @@ Each extent is described by a single fiemap_extent structure as returned in fm_extents:: struct fiemap_extent { - __u64 fe_logical; /* logical offset in bytes for the start of - * the extent */ - __u64 fe_physical; /* physical offset in bytes for the start - * of the extent */ - __u64 fe_length; /* length in bytes for the extent */ - __u64 fe_reserved64[2]; - __u32 fe_flags; /* FIEMAP_EXTENT_* flags for this extent */ - __u32 fe_reserved[3]; + /* + * logical offset in bytes for the start of + * the extent from the beginning of the file + */ + __u64 fe_logical; + /* + * physical offset in bytes for the start + * of the extent from the beginning of the disk + */ + __u64 fe_physical; + /* logical length in bytes for this extent */ + __u64 fe_logical_length; + /* physical length in bytes for this extent */ + __u64 fe_physical_length; + __u64 fe_reserved64[1]; + /* FIEMAP_EXTENT_* flags for this extent */ + __u32 fe_flags; + __u32 fe_reserved[3]; }; All offsets and lengths are in bytes and mirror those on disk. It is valid @@ -175,6 +185,8 @@ FIEMAP_EXTENT_MERGED userspace would be highly inefficient, the kernel will try to merge most adjacent blocks into 'extents'. +FIEMAP_EXTENT_HAS_PHYS_LEN + This will be set if the file system populated the physical length field. VFS -> File System Implementation --------------------------------- diff --git a/fs/ioctl.c b/fs/ioctl.c index 661b46125669..8afd32e1a27a 100644 --- a/fs/ioctl.c +++ b/fs/ioctl.c @@ -138,7 +138,8 @@ int fiemap_fill_next_extent(struct fiemap_extent_info *fieinfo, u64 logical, memset(&extent, 0, sizeof(extent)); extent.fe_logical = logical; extent.fe_physical = phys; - extent.fe_length = len; + extent.fe_logical_length = len; + extent.fe_physical_length = len; extent.fe_flags = flags; dest += fieinfo->fi_extents_mapped; diff --git a/include/uapi/linux/fiemap.h b/include/uapi/linux/fiemap.h index 24ca0c00cae3..3079159b8e94 100644 --- a/include/uapi/linux/fiemap.h +++ b/include/uapi/linux/fiemap.h @@ -14,14 +14,30 @@ #include <linux/types.h> +/* + * For backward compatibility, where the member of the struct was called + * fe_length instead of fe_logical_length. + */ +#define fe_length fe_logical_length + struct fiemap_extent { - __u64 fe_logical; /* logical offset in bytes for the start of - * the extent from the beginning of the file */ - __u64 fe_physical; /* physical offset in bytes for the start - * of the extent from the beginning of the disk */ - __u64 fe_length; /* length in bytes for this extent */ - __u64 fe_reserved64[2]; - __u32 fe_flags; /* FIEMAP_EXTENT_* flags for this extent */ + /* + * logical offset in bytes for the start of + * the extent from the beginning of the file + */ + __u64 fe_logical; + /* + * physical offset in bytes for the start + * of the extent from the beginning of the disk + */ + __u64 fe_physical; + /* logical length in bytes for this extent */ + __u64 fe_logical_length; + /* physical length in bytes for this extent */ + __u64 fe_physical_length; + __u64 fe_reserved64[1]; + /* FIEMAP_EXTENT_* flags for this extent */ + __u32 fe_flags; __u32 fe_reserved[3]; }; @@ -66,5 +82,7 @@ struct fiemap { * merged for efficiency. */ #define FIEMAP_EXTENT_SHARED 0x00002000 /* Space shared with other * files. */ +#define FIEMAP_EXTENT_HAS_PHYS_LEN 0x00004000 /* Physical length is valid + * and set by FS. */ #endif /* _UAPI_LINUX_FIEMAP_H */
Some filesystems support compressed extents which have a larger logical size than physical, and for those filesystems, it can be useful for userspace to know how much space those extents actually use. For instance, the compsize [1] tool for btrfs currently uses btrfs-internal, root-only ioctl to find the actual disk space used by a file; it would be better and more useful for this information to require fewer privileges and to be usable on more filesystems. Therefore, use one of the padding u64s in the fiemap extent structure to return the actual physical length; and, for now, return this as equal to the logical length. [1] https://github.com/kilobyte/compsize Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me> --- Documentation/filesystems/fiemap.rst | 28 +++++++++++++++++------- fs/ioctl.c | 3 ++- include/uapi/linux/fiemap.h | 32 ++++++++++++++++++++++------ 3 files changed, 47 insertions(+), 16 deletions(-)