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Message-Id: <8FBB1456-7A9F-4B0C-8FAF-B0832C874035@dilger.ca>
Date: Wed, 30 Jul 2014 14:32:12 -0600
From: Andreas Dilger <adilger@...ger.ca>
To: tytso@....edu
Cc: linux-ext4@...r.kernel.org, David Sterba <dsterba@...e.cz>
Subject: Re: [PATCH 2/3] filefrag: reserve fields and new extent flags
On Jul 30, 2014, at 2:25 PM, Andreas Dilger <adilger@...ger.ca> wrote:
> Reserve the FIEMAP_EXTENT_PHYS_LENGTH flag to indicate that the new
> fe_phys_length field contains valid data. This is introduced to
> allow different fe_phys_length and fe_logi_length values for
> compressed extents, but it is also valid to set PHYS_LENGTH and set
> fe_phys_length for regular files to simplify userspace codes. If
> PHYS_LENGTH is not set, then applications should set fe_phys_length
> equal to fe_logi_length, since fe_phys_length is undefined (though
> typically zero).
>
> Reserve the FIEMAP_EXTENT_DATA_COMPRESSED flag to allow reporting
> extents with physical length different than logical length. This
> also sets the FIEMAP_EXTENT_ENCODED flag to indicate that the data
> cannot be accessed directly.
>
> Reserve the FIEMAP_EXTENT_NET flag, which indicates that the data
> is on a network filesystem that does not have local storage devices.
> This also sets FIEMAP_EXTENT_ENCODED flag to indicate the data cannot
> be accessed directly.
>
> Print out DATA_COMPRESSED and EXTENT_NET flags in filefrag if detected.
This patch series is my first cut at filefrag updates to match David's
proposed changes to handle compressed extents in FIEMAP in the kernel.
See http://comments.gmane.org/gmane.comp.file-systems.btrfs/37312 for
the kernel side of things.
This patch series is not quite identical to what the kernel patches
are implementing, but rather how I think it should be implemented.
Feedback/discussion welcome, but I may not reply for a while.
Cheers, Andreas
> Signed-off-by: Andreas Dilger <adilger@...ger.ca>
> ---
> lib/ext2fs/fiemap.h | 17 +++++++++++++----
> misc/filefrag.c | 7 ++++++-
> 2 files changed, 19 insertions(+), 5 deletions(-)
>
> diff --git a/lib/ext2fs/fiemap.h b/lib/ext2fs/fiemap.h
> index 895cd0b..30103e2 100644
> --- a/lib/ext2fs/fiemap.h
> +++ b/lib/ext2fs/fiemap.h
> @@ -17,15 +17,17 @@ struct fiemap_extent {
> __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];
> + __u64 fe_phys_length; /* physical length in bytes for this extent,
> + * undefined if DATA_COMPRESSED not set */
> + __u64 fe_reserved64;
> __u32 fe_flags; /* FIEMAP_EXTENT_* flags for this extent */
> __u32 fe_reserved[3];
> };
>
> struct fiemap {
> - __u64 fm_start; /* logical offset (inclusive) at
> + __u64 fm_start; /* logical offset in bytes (inclusive) at
> * which to start mapping (in) */
> - __u64 fm_length; /* logical length of mapping which
> + __u64 fm_length; /* logical length in bytes of mapping which
> * userspace wants (in) */
> __u32 fm_flags; /* FIEMAP_FLAG_* flags for request (in/out) */
> __u32 fm_mapped_extents;/* number of extents that were mapped (out) */
> @@ -51,8 +53,13 @@ struct fiemap {
> * Sets EXTENT_UNKNOWN. */
> #define FIEMAP_EXTENT_ENCODED 0x00000008 /* Data can not be read
> * while fs is unmounted */
> +#define FIEMAP_EXTENT_PHYS_LENGTH 0x00000010 /* Physical length of extent
> + * in fe_phys_length valid */
> +#define FIEMAP_EXTENT_DATA_COMPRESSED 0x00000040 /* Data is compressed by fs.
> + * Sets EXTENT_ENCODED and
> + * PHYS_LENGTH. */
> #define FIEMAP_EXTENT_DATA_ENCRYPTED 0x00000080 /* Data is encrypted by fs.
> - * Sets EXTENT_NO_BYPASS. */
> + * Sets EXTENT_ENCODED. */
> #define FIEMAP_EXTENT_NOT_ALIGNED 0x00000100 /* Extent offsets may not be
> * block aligned. */
> #define FIEMAP_EXTENT_DATA_INLINE 0x00000200 /* Data mixed with metadata.
> @@ -66,5 +73,7 @@ struct fiemap {
> * merged for efficiency. */
> #define FIEMAP_EXTENT_SHARED 0x00002000 /* Space shared with other
> * files. */
> +#define FIEMAP_EXTENT_NET 0x80000000 /* Data stored remotely.
> + * Sets EXTENT_ENCODED. */
>
> #endif /* _LINUX_FIEMAP_H */
> diff --git a/misc/filefrag.c b/misc/filefrag.c
> index d71bf43..7bd100c 100644
> --- a/misc/filefrag.c
> +++ b/misc/filefrag.c
> @@ -164,6 +164,8 @@ static void print_extent_info(struct fiemap_extent *fm_extent, int cur_ex,
> print_flag(&fe_flags, FIEMAP_EXTENT_UNKNOWN, flags, "unknown_loc,");
> print_flag(&fe_flags, FIEMAP_EXTENT_DELALLOC, flags, "delalloc,");
> print_flag(&fe_flags, FIEMAP_EXTENT_ENCODED, flags, "encoded,");
> + print_flag(&fe_flags, FIEMAP_EXTENT_DATA_COMPRESSED, flags,
> + "compressed,");
> print_flag(&fe_flags, FIEMAP_EXTENT_DATA_ENCRYPTED, flags,"encrypted,");
> print_flag(&fe_flags, FIEMAP_EXTENT_NOT_ALIGNED, flags, "not_aligned,");
> print_flag(&fe_flags, FIEMAP_EXTENT_DATA_INLINE, flags, "inline,");
> @@ -171,7 +173,10 @@ static void print_extent_info(struct fiemap_extent *fm_extent, int cur_ex,
> print_flag(&fe_flags, FIEMAP_EXTENT_UNWRITTEN, flags, "unwritten,");
> print_flag(&fe_flags, FIEMAP_EXTENT_MERGED, flags, "merged,");
> print_flag(&fe_flags, FIEMAP_EXTENT_SHARED, flags, "shared,");
> - /* print any unknown flags as hex values */
> + print_flag(&fe_flags, FIEMAP_EXTENT_NET, flags, "net,");
> +
> + /* Print unknown flags in hex format. Known flags are already
> + * printed above and will have their bit cleared from "fe_flags". */
> for (mask = 1; fe_flags != 0 && mask != 0; mask <<= 1) {
> char hex[6];
>
> --
> 1.7.3.4
>
Cheers, Andreas
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