| Message ID | 1502329293-4091-6-git-send-email-allison.henderson@oracle.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
On Wed, Aug 09, 2017 at 06:41:25PM -0700, Allison Henderson wrote: > From: Dave Chinner <dchinner@redhat.com> > > We need to define the parent pointer attribute format before we > start adding support for it into all the code that needs to use it. > The EA format we will use encodes the following information: > > name={parent inode #, parent inode generation, dirent offset} > value={dirent filename} > > The inode/gen gives all the information we need to reliably identify > the parent without requiring child->parent lock ordering, and allows > userspace to do pathname component level reconstruction without the > kernel ever needing to verify the parent itself as part of ioctl > calls. > > By using the dirent offset in the EA name, we have a method of > knowing the exact parent pointer EA we need to modify/remove in > rename/unlink without an unbound EA name search. > > By keeping the dirent name in the value, we have enough information > to be able to validate and reconstruct damaged directory trees. > While the diroffset of a filename alone is not unique enough to > identify the child, the {diroffset,filename,child_inode} tuple is > sufficient. That is, if the diroffset gets reused and points to a > different filename, we can detect that from the contents of EA. If a > link of the same name is created, then we can check whether it > points at the same inode as the parent EA we current have. > > [achender: rebased, changed __unint32_t to xfs_dir2_dataptr_t] > > Signed-off-by: Dave Chinner <dchinner@redhat.com> > Signed-off-by: Allison Henderson <allison.henderson@oracle.com> > --- > :100644 100644 d4d9bef... 91e2d5a... M fs/xfs/libxfs/xfs_format.h > fs/xfs/libxfs/xfs_format.h | 27 +++++++++++++++++++++++++++ > 1 file changed, 27 insertions(+) > > diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h > index d4d9bef..91e2d5a 100644 > --- a/fs/xfs/libxfs/xfs_format.h > +++ b/fs/xfs/libxfs/xfs_format.h > @@ -18,6 +18,8 @@ > #ifndef __XFS_FORMAT_H__ > #define __XFS_FORMAT_H__ > > +#include "xfs_da_format.h" > + > /* > * XFS On Disk Format Definitions > * > @@ -1721,4 +1723,29 @@ struct xfs_acl { > #define SGI_ACL_FILE_SIZE (sizeof(SGI_ACL_FILE)-1) > #define SGI_ACL_DEFAULT_SIZE (sizeof(SGI_ACL_DEFAULT)-1) > > +/* > + * Parent pointer attribute format definition > + * > + * EA name encodes the parent inode number, generation and the offset of > + * the dirent that points to the child inode. The EA value contains the > + * same name as the dirent in the parent directory. > + */ > +struct xfs_parent_name_rec { > + __be64 p_ino; > + __be32 p_gen; > + __be32 p_diroffset; > +}; > + > +/* > + * incore version of the above, also contains name pointers so callers > + * can pass/obtain all the parent pointer information in a single structure > + */ > +struct xfs_parent_name_irec { > + uint64_t p_ino; Should use incore xfs types, i.e. xfs_ino_t. > + uint32_t p_gen; > + xfs_dir2_dataptr_t p_diroffset; > + const char *p_name; > + uint32_t p_namelen; Pathname components are at most 255 bytes long, though I guess that doesn't save us any space here. --D > +}; > + > #endif /* __XFS_FORMAT_H__ */ > -- > 2.7.4 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 08/14/2017 04:59 PM, Darrick J. Wong wrote: > On Wed, Aug 09, 2017 at 06:41:25PM -0700, Allison Henderson wrote: >> From: Dave Chinner <dchinner@redhat.com> >> >> We need to define the parent pointer attribute format before we >> start adding support for it into all the code that needs to use it. >> The EA format we will use encodes the following information: >> >> name={parent inode #, parent inode generation, dirent offset} >> value={dirent filename} >> >> The inode/gen gives all the information we need to reliably identify >> the parent without requiring child->parent lock ordering, and allows >> userspace to do pathname component level reconstruction without the >> kernel ever needing to verify the parent itself as part of ioctl >> calls. >> >> By using the dirent offset in the EA name, we have a method of >> knowing the exact parent pointer EA we need to modify/remove in >> rename/unlink without an unbound EA name search. >> >> By keeping the dirent name in the value, we have enough information >> to be able to validate and reconstruct damaged directory trees. >> While the diroffset of a filename alone is not unique enough to >> identify the child, the {diroffset,filename,child_inode} tuple is >> sufficient. That is, if the diroffset gets reused and points to a >> different filename, we can detect that from the contents of EA. If a >> link of the same name is created, then we can check whether it >> points at the same inode as the parent EA we current have. >> >> [achender: rebased, changed __unint32_t to xfs_dir2_dataptr_t] >> >> Signed-off-by: Dave Chinner <dchinner@redhat.com> >> Signed-off-by: Allison Henderson <allison.henderson@oracle.com> >> --- >> :100644 100644 d4d9bef... 91e2d5a... M fs/xfs/libxfs/xfs_format.h >> fs/xfs/libxfs/xfs_format.h | 27 +++++++++++++++++++++++++++ >> 1 file changed, 27 insertions(+) >> >> diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h >> index d4d9bef..91e2d5a 100644 >> --- a/fs/xfs/libxfs/xfs_format.h >> +++ b/fs/xfs/libxfs/xfs_format.h >> @@ -18,6 +18,8 @@ >> #ifndef __XFS_FORMAT_H__ >> #define __XFS_FORMAT_H__ >> >> +#include "xfs_da_format.h" >> + >> /* >> * XFS On Disk Format Definitions >> * >> @@ -1721,4 +1723,29 @@ struct xfs_acl { >> #define SGI_ACL_FILE_SIZE (sizeof(SGI_ACL_FILE)-1) >> #define SGI_ACL_DEFAULT_SIZE (sizeof(SGI_ACL_DEFAULT)-1) >> >> +/* >> + * Parent pointer attribute format definition >> + * >> + * EA name encodes the parent inode number, generation and the offset of >> + * the dirent that points to the child inode. The EA value contains the >> + * same name as the dirent in the parent directory. >> + */ >> +struct xfs_parent_name_rec { >> + __be64 p_ino; >> + __be32 p_gen; >> + __be32 p_diroffset; >> +}; >> + >> +/* >> + * incore version of the above, also contains name pointers so callers >> + * can pass/obtain all the parent pointer information in a single structure >> + */ >> +struct xfs_parent_name_irec { >> + uint64_t p_ino; > Should use incore xfs types, i.e. xfs_ino_t. Ok, will fix >> + uint32_t p_gen; >> + xfs_dir2_dataptr_t p_diroffset; >> + const char *p_name; >> + uint32_t p_namelen; > Pathname components are at most 255 bytes long, though I guess that > doesn't save us any space here. Ok, I'll update it to use a uint8_t, parameters get shifted around all the time. Allison > --D > >> +}; >> + >> #endif /* __XFS_FORMAT_H__ */ >> -- >> 2.7.4 >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-xfs" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h index d4d9bef..91e2d5a 100644 --- a/fs/xfs/libxfs/xfs_format.h +++ b/fs/xfs/libxfs/xfs_format.h @@ -18,6 +18,8 @@ #ifndef __XFS_FORMAT_H__ #define __XFS_FORMAT_H__ +#include "xfs_da_format.h" + /* * XFS On Disk Format Definitions * @@ -1721,4 +1723,29 @@ struct xfs_acl { #define SGI_ACL_FILE_SIZE (sizeof(SGI_ACL_FILE)-1) #define SGI_ACL_DEFAULT_SIZE (sizeof(SGI_ACL_DEFAULT)-1) +/* + * Parent pointer attribute format definition + * + * EA name encodes the parent inode number, generation and the offset of + * the dirent that points to the child inode. The EA value contains the + * same name as the dirent in the parent directory. + */ +struct xfs_parent_name_rec { + __be64 p_ino; + __be32 p_gen; + __be32 p_diroffset; +}; + +/* + * incore version of the above, also contains name pointers so callers + * can pass/obtain all the parent pointer information in a single structure + */ +struct xfs_parent_name_irec { + uint64_t p_ino; + uint32_t p_gen; + xfs_dir2_dataptr_t p_diroffset; + const char *p_name; + uint32_t p_namelen; +}; + #endif /* __XFS_FORMAT_H__ */