| Message ID | CAOQ4uxg+qSLP0KwdW+h1tcPqOCQd+_pGZVXiePQB1TXCMBMctQ@mail.gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, Apr 23 2018, Amir Goldstein wrote: > tmpfs uses the helper d_find_alias() to find a dentry from a decoded > inode, but d_find_alias() skips unhashed dentries, so unlinked files > cannot be decoded from a file handle. > > This can be reproduced using xfstests test program open_by_handle: > $ open_by handle -c /tmp/testdir > $ open_by_handle -dk /tmp/testdir > open_by_handle(/tmp/testdir/file000000) returned 116 incorrectly on an > unlinked open file! > > To fix this, if d_find_alias() can't find a hashed alias, call > d_find_any_alias() to return an unhashed one. > > Cc: Hugh Dickins <hughd@google.com> > Cc: Al Viro <viro@zeniv.linux.org.uk> > Signed-off-by: Amir Goldstein <amir73il@gmail.com> Reviewed-by: NeilBrown <neilb@suse.com> Looks reasonable to me. You could possibly just use d_find_any_alias() unconditionally, but there is sometimes a small benefit in getting a hashed aliases if there is one. Thanks, NeilBrown > --- > > Hi Andrew, > > I was nudging Hugh over at LSF/MM about this patch and he has > suggested that I send it to you, because he has no idea about the > exportfs parts. > > The test for decoding a file handle of an unlinked file has already > been merged to xfstest generic/467 and the test is failing on tmpfs > without this change. > > Can you please take this patch. > > Thanks, > Amir. > > mm/shmem.c | 11 ++++++++++- > 1 file changed, 10 insertions(+), 1 deletion(-) > > diff --git a/mm/shmem.c b/mm/shmem.c > index 07a1d22807be..5d3fa4099f54 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -3404,6 +3404,15 @@ static int shmem_match(struct inode *ino, void *vfh) > return ino->i_ino == inum && fh[0] == ino->i_generation; > } > > +/* Find any alias of inode, but prefer a hashed alias */ > +static struct dentry *shmem_find_alias(struct inode *inode) > +{ > + struct dentry *alias = d_find_alias(inode); > + > + return alias ?: d_find_any_alias(inode); > +} > + > + > static struct dentry *shmem_fh_to_dentry(struct super_block *sb, > struct fid *fid, int fh_len, int fh_type) > { > @@ -3420,7 +3429,7 @@ static struct dentry *shmem_fh_to_dentry(struct > super_block *sb, > inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]), > shmem_match, fid->raw); > if (inode) { > - dentry = d_find_alias(inode); > + dentry = shmem_find_alias(inode); > iput(inode); > } > > -- > 2.7.4
diff --git a/mm/shmem.c b/mm/shmem.c index 07a1d22807be..5d3fa4099f54 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -3404,6 +3404,15 @@ static int shmem_match(struct inode *ino, void *vfh) return ino->i_ino == inum && fh[0] == ino->i_generation; } +/* Find any alias of inode, but prefer a hashed alias */ +static struct dentry *shmem_find_alias(struct inode *inode) +{ + struct dentry *alias = d_find_alias(inode); + + return alias ?: d_find_any_alias(inode); +} + + static struct dentry *shmem_fh_to_dentry(struct super_block *sb, struct fid *fid, int fh_len, int fh_type) { @@ -3420,7 +3429,7 @@ static struct dentry *shmem_fh_to_dentry(struct super_block *sb, inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]), shmem_match, fid->raw); if (inode) { - dentry = d_find_alias(inode); + dentry = shmem_find_alias(inode); iput(inode); }
tmpfs uses the helper d_find_alias() to find a dentry from a decoded inode, but d_find_alias() skips unhashed dentries, so unlinked files cannot be decoded from a file handle. This can be reproduced using xfstests test program open_by_handle: $ open_by handle -c /tmp/testdir $ open_by_handle -dk /tmp/testdir open_by_handle(/tmp/testdir/file000000) returned 116 incorrectly on an unlinked open file! To fix this, if d_find_alias() can't find a hashed alias, call d_find_any_alias() to return an unhashed one. Cc: Hugh Dickins <hughd@google.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Amir Goldstein <amir73il@gmail.com> --- Hi Andrew, I was nudging Hugh over at LSF/MM about this patch and he has suggested that I send it to you, because he has no idea about the exportfs parts. The test for decoding a file handle of an unlinked file has already been merged to xfstest generic/467 and the test is failing on tmpfs without this change. Can you please take this patch. Thanks, Amir. mm/shmem.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) -- 2.7.4