* [PATCH] f2fs: fix multiple f2fs_add_link() calls having same name @ 2017-02-14 18:03 Jaegeuk Kim 2017-02-15 1:18 ` [f2fs-dev] " Chao Yu 0 siblings, 1 reply; 6+ messages in thread From: Jaegeuk Kim @ 2017-02-14 18:03 UTC (permalink / raw) To: linux-kernel, linux-fsdevel, linux-f2fs-devel; +Cc: Jaegeuk Kim, stable VFS uses f2fs_lookup() to decide f2fs_add_link() call during file creation. But, if there is a race condition, f2fs_add_link() can be called multiple times, resulting in multiple dentries with a same name. This patches fixes it by adding __f2fs_find_entry() in f2fs_add_link() path. Cc: <stable@vger.kernel.org> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org> --- fs/f2fs/dir.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c index 827c5daef4fc..bc7c48839bec 100644 --- a/fs/f2fs/dir.c +++ b/fs/f2fs/dir.c @@ -643,14 +643,24 @@ int __f2fs_add_link(struct inode *dir, const struct qstr *name, struct inode *inode, nid_t ino, umode_t mode) { struct fscrypt_name fname; + struct page *page; + struct f2fs_dir_entry *de; int err; err = fscrypt_setup_filename(dir, name, 0, &fname); if (err) return err; - err = __f2fs_do_add_link(dir, &fname, inode, ino, mode); - + de = __f2fs_find_entry(dir, &fname, &page); + if (de) { + f2fs_dentry_kunmap(dir, page); + f2fs_put_page(page, 0); + err = -EEXIST; + } else if (!IS_ERR(page)) { + err = __f2fs_do_add_link(dir, &fname, inode, ino, mode); + } else { + err = PTR_ERR(page); + } fscrypt_free_filename(&fname); return err; } -- 2.11.0 ^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [f2fs-dev] [PATCH] f2fs: fix multiple f2fs_add_link() calls having same name 2017-02-14 18:03 [PATCH] f2fs: fix multiple f2fs_add_link() calls having same name Jaegeuk Kim @ 2017-02-15 1:18 ` Chao Yu 2017-02-15 1:39 ` Jaegeuk Kim 0 siblings, 1 reply; 6+ messages in thread From: Chao Yu @ 2017-02-15 1:18 UTC (permalink / raw) To: Jaegeuk Kim, linux-kernel, linux-fsdevel, linux-f2fs-devel; +Cc: stable On 2017/2/15 2:03, Jaegeuk Kim wrote: > VFS uses f2fs_lookup() to decide f2fs_add_link() call during file creation. > But, if there is a race condition, f2fs_add_link() can be called multiple > times, resulting in multiple dentries with a same name. This patches fixes > it by adding __f2fs_find_entry() in f2fs_add_link() path. As during ->lookup, i_mutex will be held all the time, so there is no race condition in between different file creators? Thanks, > > Cc: <stable@vger.kernel.org> > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org> > --- > fs/f2fs/dir.c | 14 ++++++++++++-- > 1 file changed, 12 insertions(+), 2 deletions(-) > > diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c > index 827c5daef4fc..bc7c48839bec 100644 > --- a/fs/f2fs/dir.c > +++ b/fs/f2fs/dir.c > @@ -643,14 +643,24 @@ int __f2fs_add_link(struct inode *dir, const struct qstr *name, > struct inode *inode, nid_t ino, umode_t mode) > { > struct fscrypt_name fname; > + struct page *page; > + struct f2fs_dir_entry *de; > int err; > > err = fscrypt_setup_filename(dir, name, 0, &fname); > if (err) > return err; > > - err = __f2fs_do_add_link(dir, &fname, inode, ino, mode); > - > + de = __f2fs_find_entry(dir, &fname, &page); > + if (de) { > + f2fs_dentry_kunmap(dir, page); > + f2fs_put_page(page, 0); > + err = -EEXIST; > + } else if (!IS_ERR(page)) { > + err = __f2fs_do_add_link(dir, &fname, inode, ino, mode); > + } else { > + err = PTR_ERR(page); > + } > fscrypt_free_filename(&fname); > return err; > } > ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [f2fs-dev] [PATCH] f2fs: fix multiple f2fs_add_link() calls having same name 2017-02-15 1:18 ` [f2fs-dev] " Chao Yu @ 2017-02-15 1:39 ` Jaegeuk Kim 2017-02-16 1:16 ` Jaegeuk Kim 0 siblings, 1 reply; 6+ messages in thread From: Jaegeuk Kim @ 2017-02-15 1:39 UTC (permalink / raw) To: Chao Yu; +Cc: linux-kernel, linux-fsdevel, linux-f2fs-devel, stable On 02/15, Chao Yu wrote: > On 2017/2/15 2:03, Jaegeuk Kim wrote: > > VFS uses f2fs_lookup() to decide f2fs_add_link() call during file creation. > > But, if there is a race condition, f2fs_add_link() can be called multiple > > times, resulting in multiple dentries with a same name. This patches fixes > > it by adding __f2fs_find_entry() in f2fs_add_link() path. > > As during ->lookup, i_mutex will be held all the time, so there is no race > condition in between different file creators? Hehe, yup. I dropped this patch. Thanks, > > Thanks, > > > > > Cc: <stable@vger.kernel.org> > > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org> > > --- > > fs/f2fs/dir.c | 14 ++++++++++++-- > > 1 file changed, 12 insertions(+), 2 deletions(-) > > > > diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c > > index 827c5daef4fc..bc7c48839bec 100644 > > --- a/fs/f2fs/dir.c > > +++ b/fs/f2fs/dir.c > > @@ -643,14 +643,24 @@ int __f2fs_add_link(struct inode *dir, const struct qstr *name, > > struct inode *inode, nid_t ino, umode_t mode) > > { > > struct fscrypt_name fname; > > + struct page *page; > > + struct f2fs_dir_entry *de; > > int err; > > > > err = fscrypt_setup_filename(dir, name, 0, &fname); > > if (err) > > return err; > > > > - err = __f2fs_do_add_link(dir, &fname, inode, ino, mode); > > - > > + de = __f2fs_find_entry(dir, &fname, &page); > > + if (de) { > > + f2fs_dentry_kunmap(dir, page); > > + f2fs_put_page(page, 0); > > + err = -EEXIST; > > + } else if (!IS_ERR(page)) { > > + err = __f2fs_do_add_link(dir, &fname, inode, ino, mode); > > + } else { > > + err = PTR_ERR(page); > > + } > > fscrypt_free_filename(&fname); > > return err; > > } > > ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [f2fs-dev] [PATCH] f2fs: fix multiple f2fs_add_link() calls having same name 2017-02-15 1:39 ` Jaegeuk Kim @ 2017-02-16 1:16 ` Jaegeuk Kim 2017-02-16 3:37 ` Chao Yu 0 siblings, 1 reply; 6+ messages in thread From: Jaegeuk Kim @ 2017-02-16 1:16 UTC (permalink / raw) To: Chao Yu; +Cc: linux-fsdevel, linux-kernel, stable, linux-f2fs-devel On 02/14, Jaegeuk Kim wrote: > On 02/15, Chao Yu wrote: > > On 2017/2/15 2:03, Jaegeuk Kim wrote: > > > VFS uses f2fs_lookup() to decide f2fs_add_link() call during file creation. > > > But, if there is a race condition, f2fs_add_link() can be called multiple > > > times, resulting in multiple dentries with a same name. This patches fixes > > > it by adding __f2fs_find_entry() in f2fs_add_link() path. > > > > As during ->lookup, i_mutex will be held all the time, so there is no race > > condition in between different file creators? > > Hehe, yup. > I dropped this patch. It turns out sdcardfs has a race condition between lookup and create, and it calls vfs_create() twice. Workaround by f2fs would be needed for whole AOSP as well. And I added to check current to avoid performance regression. Thanks, >From 2f433dbfa491550e666a3d08f5a59ac5bed42b0f Mon Sep 17 00:00:00 2001 From: Jaegeuk Kim <jaegeuk@kernel.org> Date: Tue, 14 Feb 2017 09:54:37 -0800 Subject: [PATCH] f2fs: fix multiple f2fs_add_link() calls having same name It turns out a stakable filesystem like sdcardfs in AOSP can trigger multiple vfs_create() to lower filesystem. In that case, f2fs will add multiple dentries having same name which breaks filesystem consistency. Until upper layer fixes, let's work around by f2fs, which shows actually not much performance regression. Cc: <stable@vger.kernel.org> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org> --- fs/f2fs/dir.c | 26 ++++++++++++++++++++++++-- fs/f2fs/f2fs.h | 1 + 2 files changed, 25 insertions(+), 2 deletions(-) diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c index 827c5daef4fc..4f5b3bb514c6 100644 --- a/fs/f2fs/dir.c +++ b/fs/f2fs/dir.c @@ -207,9 +207,11 @@ static struct f2fs_dir_entry *find_in_level(struct inode *dir, f2fs_put_page(dentry_page, 0); } + /* This is to increase the speed of f2fs_create */ if (!de && room && F2FS_I(dir)->chash != namehash) { F2FS_I(dir)->chash = namehash; F2FS_I(dir)->clevel = level; + F2FS_I(dir)->task = current; } return de; @@ -643,14 +645,34 @@ int __f2fs_add_link(struct inode *dir, const struct qstr *name, struct inode *inode, nid_t ino, umode_t mode) { struct fscrypt_name fname; + struct page *page = NULL; + struct f2fs_dir_entry *de = NULL; int err; err = fscrypt_setup_filename(dir, name, 0, &fname); if (err) return err; - err = __f2fs_do_add_link(dir, &fname, inode, ino, mode); - + /* + * An immature stakable filesystem shows a race condition between lookup + * and create. If we have same task when doing lookup and create, it's + * definitely fine as expected by VFS normally. Otherwise, let's just + * verify on-disk dentry one more time, which guarantees filesystem + * consistency more. + */ + if (current != F2FS_I(dir)->task) { + de = __f2fs_find_entry(dir, &fname, &page); + F2FS_I(dir)->task = NULL; + } + if (de) { + f2fs_dentry_kunmap(dir, page); + f2fs_put_page(page, 0); + err = -EEXIST; + } else if (!IS_ERR(page)) { + err = __f2fs_do_add_link(dir, &fname, inode, ino, mode); + } else { + err = PTR_ERR(page); + } fscrypt_free_filename(&fname); return err; } diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h index d263dade5e4c..cc22dc458896 100644 --- a/fs/f2fs/f2fs.h +++ b/fs/f2fs/f2fs.h @@ -454,6 +454,7 @@ struct f2fs_inode_info { atomic_t dirty_pages; /* # of dirty pages */ f2fs_hash_t chash; /* hash value of given file name */ unsigned int clevel; /* maximum level of given file name */ + struct task_struct *task; /* lookup and create consistency */ nid_t i_xattr_nid; /* node id that contains xattrs */ loff_t last_disk_size; /* lastly written file size */ -- 2.11.0 ^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [f2fs-dev] [PATCH] f2fs: fix multiple f2fs_add_link() calls having same name 2017-02-16 1:16 ` Jaegeuk Kim @ 2017-02-16 3:37 ` Chao Yu 2017-02-16 17:28 ` Jaegeuk Kim 0 siblings, 1 reply; 6+ messages in thread From: Chao Yu @ 2017-02-16 3:37 UTC (permalink / raw) To: Jaegeuk Kim; +Cc: linux-fsdevel, linux-kernel, stable, linux-f2fs-devel On 2017/2/16 9:16, Jaegeuk Kim wrote: > On 02/14, Jaegeuk Kim wrote: >> On 02/15, Chao Yu wrote: >>> On 2017/2/15 2:03, Jaegeuk Kim wrote: >>>> VFS uses f2fs_lookup() to decide f2fs_add_link() call during file creation. >>>> But, if there is a race condition, f2fs_add_link() can be called multiple >>>> times, resulting in multiple dentries with a same name. This patches fixes >>>> it by adding __f2fs_find_entry() in f2fs_add_link() path. >>> >>> As during ->lookup, i_mutex will be held all the time, so there is no race >>> condition in between different file creators? >> >> Hehe, yup. >> I dropped this patch. > > It turns out sdcardfs has a race condition between lookup and create, and it > calls vfs_create() twice. Workaround by f2fs would be needed for whole AOSP as > well. And I added to check current to avoid performance regression. > > Thanks, > >>From 2f433dbfa491550e666a3d08f5a59ac5bed42b0f Mon Sep 17 00:00:00 2001 > From: Jaegeuk Kim <jaegeuk@kernel.org> > Date: Tue, 14 Feb 2017 09:54:37 -0800 > Subject: [PATCH] f2fs: fix multiple f2fs_add_link() calls having same name > > It turns out a stakable filesystem like sdcardfs in AOSP can trigger multiple > vfs_create() to lower filesystem. In that case, f2fs will add multiple dentries > having same name which breaks filesystem consistency. > > Until upper layer fixes, let's work around by f2fs, which shows actually not > much performance regression. > > Cc: <stable@vger.kernel.org> > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org> > --- > fs/f2fs/dir.c | 26 ++++++++++++++++++++++++-- > fs/f2fs/f2fs.h | 1 + > 2 files changed, 25 insertions(+), 2 deletions(-) > > diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c > index 827c5daef4fc..4f5b3bb514c6 100644 > --- a/fs/f2fs/dir.c > +++ b/fs/f2fs/dir.c > @@ -207,9 +207,11 @@ static struct f2fs_dir_entry *find_in_level(struct inode *dir, > f2fs_put_page(dentry_page, 0); > } > > + /* This is to increase the speed of f2fs_create */ > if (!de && room && F2FS_I(dir)->chash != namehash) { > F2FS_I(dir)->chash = namehash; > F2FS_I(dir)->clevel = level; > + F2FS_I(dir)->task = current; > } Hash collision can happen on different file names, here, assignment of .task should be more accurately to prevent racing between lookup and creat, so how about: if (!de && room) { .task = current; if (chash != namehash) { .chash = namehash; .clevel = level; } } Thanks, > > return de; > @@ -643,14 +645,34 @@ int __f2fs_add_link(struct inode *dir, const struct qstr *name, > struct inode *inode, nid_t ino, umode_t mode) > { > struct fscrypt_name fname; > + struct page *page = NULL; > + struct f2fs_dir_entry *de = NULL; > int err; > > err = fscrypt_setup_filename(dir, name, 0, &fname); > if (err) > return err; > > - err = __f2fs_do_add_link(dir, &fname, inode, ino, mode); > - > + /* > + * An immature stakable filesystem shows a race condition between lookup > + * and create. If we have same task when doing lookup and create, it's > + * definitely fine as expected by VFS normally. Otherwise, let's just > + * verify on-disk dentry one more time, which guarantees filesystem > + * consistency more. > + */ > + if (current != F2FS_I(dir)->task) { > + de = __f2fs_find_entry(dir, &fname, &page); > + F2FS_I(dir)->task = NULL; > + } > + if (de) { > + f2fs_dentry_kunmap(dir, page); > + f2fs_put_page(page, 0); > + err = -EEXIST; > + } else if (!IS_ERR(page)) { > + err = __f2fs_do_add_link(dir, &fname, inode, ino, mode); > + } else { > + err = PTR_ERR(page); > + } > fscrypt_free_filename(&fname); > return err; > } > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h > index d263dade5e4c..cc22dc458896 100644 > --- a/fs/f2fs/f2fs.h > +++ b/fs/f2fs/f2fs.h > @@ -454,6 +454,7 @@ struct f2fs_inode_info { > atomic_t dirty_pages; /* # of dirty pages */ > f2fs_hash_t chash; /* hash value of given file name */ > unsigned int clevel; /* maximum level of given file name */ > + struct task_struct *task; /* lookup and create consistency */ > nid_t i_xattr_nid; /* node id that contains xattrs */ > loff_t last_disk_size; /* lastly written file size */ > > ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [f2fs-dev] [PATCH] f2fs: fix multiple f2fs_add_link() calls having same name 2017-02-16 3:37 ` Chao Yu @ 2017-02-16 17:28 ` Jaegeuk Kim 0 siblings, 0 replies; 6+ messages in thread From: Jaegeuk Kim @ 2017-02-16 17:28 UTC (permalink / raw) To: Chao Yu; +Cc: linux-fsdevel, linux-kernel, stable, linux-f2fs-devel On 02/16, Chao Yu wrote: > On 2017/2/16 9:16, Jaegeuk Kim wrote: > > On 02/14, Jaegeuk Kim wrote: > >> On 02/15, Chao Yu wrote: > >>> On 2017/2/15 2:03, Jaegeuk Kim wrote: > >>>> VFS uses f2fs_lookup() to decide f2fs_add_link() call during file creation. > >>>> But, if there is a race condition, f2fs_add_link() can be called multiple > >>>> times, resulting in multiple dentries with a same name. This patches fixes > >>>> it by adding __f2fs_find_entry() in f2fs_add_link() path. > >>> > >>> As during ->lookup, i_mutex will be held all the time, so there is no race > >>> condition in between different file creators? > >> > >> Hehe, yup. > >> I dropped this patch. > > > > It turns out sdcardfs has a race condition between lookup and create, and it > > calls vfs_create() twice. Workaround by f2fs would be needed for whole AOSP as > > well. And I added to check current to avoid performance regression. > > > > Thanks, > > > >>From 2f433dbfa491550e666a3d08f5a59ac5bed42b0f Mon Sep 17 00:00:00 2001 > > From: Jaegeuk Kim <jaegeuk@kernel.org> > > Date: Tue, 14 Feb 2017 09:54:37 -0800 > > Subject: [PATCH] f2fs: fix multiple f2fs_add_link() calls having same name > > > > It turns out a stakable filesystem like sdcardfs in AOSP can trigger multiple > > vfs_create() to lower filesystem. In that case, f2fs will add multiple dentries > > having same name which breaks filesystem consistency. > > > > Until upper layer fixes, let's work around by f2fs, which shows actually not > > much performance regression. > > > > Cc: <stable@vger.kernel.org> > > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org> > > --- > > fs/f2fs/dir.c | 26 ++++++++++++++++++++++++-- > > fs/f2fs/f2fs.h | 1 + > > 2 files changed, 25 insertions(+), 2 deletions(-) > > > > diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c > > index 827c5daef4fc..4f5b3bb514c6 100644 > > --- a/fs/f2fs/dir.c > > +++ b/fs/f2fs/dir.c > > @@ -207,9 +207,11 @@ static struct f2fs_dir_entry *find_in_level(struct inode *dir, > > f2fs_put_page(dentry_page, 0); > > } > > > > + /* This is to increase the speed of f2fs_create */ > > if (!de && room && F2FS_I(dir)->chash != namehash) { > > F2FS_I(dir)->chash = namehash; > > F2FS_I(dir)->clevel = level; > > + F2FS_I(dir)->task = current; > > } > > Hash collision can happen on different file names, here, assignment of .task > should be more accurately to prevent racing between lookup and creat, so how about: > > if (!de && room) { > .task = current; > if (chash != namehash) { > .chash = namehash; > .clevel = level; > } > } Makes sense. Will apply that. ;) Thanks, > > Thanks, > > > > > return de; > > @@ -643,14 +645,34 @@ int __f2fs_add_link(struct inode *dir, const struct qstr *name, > > struct inode *inode, nid_t ino, umode_t mode) > > { > > struct fscrypt_name fname; > > + struct page *page = NULL; > > + struct f2fs_dir_entry *de = NULL; > > int err; > > > > err = fscrypt_setup_filename(dir, name, 0, &fname); > > if (err) > > return err; > > > > - err = __f2fs_do_add_link(dir, &fname, inode, ino, mode); > > - > > + /* > > + * An immature stakable filesystem shows a race condition between lookup > > + * and create. If we have same task when doing lookup and create, it's > > + * definitely fine as expected by VFS normally. Otherwise, let's just > > + * verify on-disk dentry one more time, which guarantees filesystem > > + * consistency more. > > + */ > > + if (current != F2FS_I(dir)->task) { > > + de = __f2fs_find_entry(dir, &fname, &page); > > + F2FS_I(dir)->task = NULL; > > + } > > + if (de) { > > + f2fs_dentry_kunmap(dir, page); > > + f2fs_put_page(page, 0); > > + err = -EEXIST; > > + } else if (!IS_ERR(page)) { > > + err = __f2fs_do_add_link(dir, &fname, inode, ino, mode); > > + } else { > > + err = PTR_ERR(page); > > + } > > fscrypt_free_filename(&fname); > > return err; > > } > > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h > > index d263dade5e4c..cc22dc458896 100644 > > --- a/fs/f2fs/f2fs.h > > +++ b/fs/f2fs/f2fs.h > > @@ -454,6 +454,7 @@ struct f2fs_inode_info { > > atomic_t dirty_pages; /* # of dirty pages */ > > f2fs_hash_t chash; /* hash value of given file name */ > > unsigned int clevel; /* maximum level of given file name */ > > + struct task_struct *task; /* lookup and create consistency */ > > nid_t i_xattr_nid; /* node id that contains xattrs */ > > loff_t last_disk_size; /* lastly written file size */ > > > > ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2017-02-16 17:28 UTC | newest] Thread overview: 6+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2017-02-14 18:03 [PATCH] f2fs: fix multiple f2fs_add_link() calls having same name Jaegeuk Kim 2017-02-15 1:18 ` [f2fs-dev] " Chao Yu 2017-02-15 1:39 ` Jaegeuk Kim 2017-02-16 1:16 ` Jaegeuk Kim 2017-02-16 3:37 ` Chao Yu 2017-02-16 17:28 ` Jaegeuk Kim
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