| Message ID | 20230422-uring-getdents-v2-4-2db1e37dc55e@codewreck.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | io_uring: add getdents support, take 2 | expand |
Hi Dominique,
kernel test robot noticed the following build warnings:
url: https://github.com/intel-lab-lkp/linux/commits/Dominique-Martinet/fs-split-off-vfs_getdents-function-of-getdents64-syscall/20230510-185542
base: 58390c8ce1bddb6c623f62e7ed36383e7fa5c02f
patch link: https://lore.kernel.org/r/20230422-uring-getdents-v2-4-2db1e37dc55e%40codewreck.org
patch subject: [PATCH v2 4/6] kernfs: implement readdir FMODE_NOWAIT
config: i386-randconfig-m021 (https://download.01.org/0day-ci/archive/20230511/202305110647.eSnSEulg-lkp@intel.com/config)
compiler: gcc-11 (Debian 11.3.0-12) 11.3.0
If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Reported-by: Dan Carpenter <error27@gmail.com>
| Link: https://lore.kernel.org/r/202305110647.eSnSEulg-lkp@intel.com/
smatch warnings:
fs/kernfs/dir.c:1863 kernfs_fop_readdir() warn: inconsistent returns '&root->kernfs_rwsem'.
vim +1863 fs/kernfs/dir.c
c637b8acbe079e Tejun Heo 2013-12-11 1815 static int kernfs_fop_readdir(struct file *file, struct dir_context *ctx)
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1816 {
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1817 struct dentry *dentry = file->f_path.dentry;
319ba91d352a74 Shaohua Li 2017-07-12 1818 struct kernfs_node *parent = kernfs_dentry_node(dentry);
324a56e16e44ba Tejun Heo 2013-12-11 1819 struct kernfs_node *pos = file->private_data;
393c3714081a53 Minchan Kim 2021-11-18 1820 struct kernfs_root *root;
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1821 const void *ns = NULL;
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1822
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1823 if (!dir_emit_dots(file, ctx))
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1824 return 0;
393c3714081a53 Minchan Kim 2021-11-18 1825
393c3714081a53 Minchan Kim 2021-11-18 1826 root = kernfs_root(parent);
a551138c4b3b9f Dominique Martinet 2023-05-10 1827 if (ctx->flags & DIR_CONTEXT_F_NOWAIT) {
a551138c4b3b9f Dominique Martinet 2023-05-10 1828 if (!down_read_trylock(&root->kernfs_rwsem))
a551138c4b3b9f Dominique Martinet 2023-05-10 1829 return -EAGAIN;
a551138c4b3b9f Dominique Martinet 2023-05-10 1830 } else {
393c3714081a53 Minchan Kim 2021-11-18 1831 down_read(&root->kernfs_rwsem);
a551138c4b3b9f Dominique Martinet 2023-05-10 1832 }
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1833
324a56e16e44ba Tejun Heo 2013-12-11 1834 if (kernfs_ns_enabled(parent))
c525aaddc366df Tejun Heo 2013-12-11 1835 ns = kernfs_info(dentry->d_sb)->ns;
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1836
c637b8acbe079e Tejun Heo 2013-12-11 1837 for (pos = kernfs_dir_pos(ns, parent, ctx->pos, pos);
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1838 pos;
c637b8acbe079e Tejun Heo 2013-12-11 1839 pos = kernfs_dir_next_pos(ns, parent, ctx->pos, pos)) {
adc5e8b58f4886 Tejun Heo 2013-12-11 1840 const char *name = pos->name;
364595a6851bf6 Jeff Layton 2023-03-30 1841 unsigned int type = fs_umode_to_dtype(pos->mode);
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1842 int len = strlen(name);
67c0496e87d193 Tejun Heo 2019-11-04 1843 ino_t ino = kernfs_ino(pos);
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1844
adc5e8b58f4886 Tejun Heo 2013-12-11 1845 ctx->pos = pos->hash;
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1846 file->private_data = pos;
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1847 kernfs_get(pos);
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1848
393c3714081a53 Minchan Kim 2021-11-18 1849 up_read(&root->kernfs_rwsem);
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1850 if (!dir_emit(ctx, name, len, ino, type))
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1851 return 0;
393c3714081a53 Minchan Kim 2021-11-18 1852 down_read(&root->kernfs_rwsem);
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Needs to be deleted.
a551138c4b3b9f Dominique Martinet 2023-05-10 1853 if (ctx->flags & DIR_CONTEXT_F_NOWAIT) {
a551138c4b3b9f Dominique Martinet 2023-05-10 1854 if (!down_read_trylock(&root->kernfs_rwsem))
a551138c4b3b9f Dominique Martinet 2023-05-10 1855 return 0;
It's a bit strange the this doesn't return -EAGAIN;
a551138c4b3b9f Dominique Martinet 2023-05-10 1856 } else {
a551138c4b3b9f Dominique Martinet 2023-05-10 1857 down_read(&root->kernfs_rwsem);
a551138c4b3b9f Dominique Martinet 2023-05-10 1858 }
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1859 }
393c3714081a53 Minchan Kim 2021-11-18 1860 up_read(&root->kernfs_rwsem);
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1861 file->private_data = NULL;
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1862 ctx->pos = INT_MAX;
fd7b9f7b9776b1 Tejun Heo 2013-11-28 @1863 return 0;
fd7b9f7b9776b1 Tejun Heo 2013-11-28 1864 }
Dan Carpenter wrote on Thu, May 11, 2023 at 01:55:57PM +0300: > fd7b9f7b9776b1 Tejun Heo 2013-11-28 1850 if (!dir_emit(ctx, name, len, ino, type)) > fd7b9f7b9776b1 Tejun Heo 2013-11-28 1851 return 0; > 393c3714081a53 Minchan Kim 2021-11-18 1852 down_read(&root->kernfs_rwsem); > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > Needs to be deleted. Uh, yes, sorry; I'm not sure how I let that slip, I guess I didn't hit any dead lock because nothing ever tried to take a write lock after getdents... Thanks! I expect there'll be other comments (this might not make it at all), so I'll keep the v3 of this patch with this fix locally and resend after other comments. > a551138c4b3b9f Dominique Martinet 2023-05-10 1853 if (ctx->flags & DIR_CONTEXT_F_NOWAIT) { > a551138c4b3b9f Dominique Martinet 2023-05-10 1854 if (!down_read_trylock(&root->kernfs_rwsem)) > a551138c4b3b9f Dominique Martinet 2023-05-10 1855 return 0; > > It's a bit strange the this doesn't return -EAGAIN; That is on purpose: the getdents did work (dir_emit returned success at least once), so the caller can process whatever was filled in the buffer before calling iterate_shared() again. If we were to return -EAGAIN here, we'd actually be throwing out the entries we just filled in, and that's not what we want.
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c index 45b6919903e6..5a5b3e7881bf 100644 --- a/fs/kernfs/dir.c +++ b/fs/kernfs/dir.c @@ -1824,7 +1824,12 @@ static int kernfs_fop_readdir(struct file *file, struct dir_context *ctx) return 0; root = kernfs_root(parent); - down_read(&root->kernfs_rwsem); + if (ctx->flags & DIR_CONTEXT_F_NOWAIT) { + if (!down_read_trylock(&root->kernfs_rwsem)) + return -EAGAIN; + } else { + down_read(&root->kernfs_rwsem); + } if (kernfs_ns_enabled(parent)) ns = kernfs_info(dentry->d_sb)->ns; @@ -1845,6 +1850,12 @@ static int kernfs_fop_readdir(struct file *file, struct dir_context *ctx) if (!dir_emit(ctx, name, len, ino, type)) return 0; down_read(&root->kernfs_rwsem); + if (ctx->flags & DIR_CONTEXT_F_NOWAIT) { + if (!down_read_trylock(&root->kernfs_rwsem)) + return 0; + } else { + down_read(&root->kernfs_rwsem); + } } up_read(&root->kernfs_rwsem); file->private_data = NULL; @@ -1852,7 +1863,14 @@ static int kernfs_fop_readdir(struct file *file, struct dir_context *ctx) return 0; } +static int kernfs_fop_dir_open(struct inode *inode, struct file *file) +{ + file->f_mode |= FMODE_NOWAIT; + return 0; +} + const struct file_operations kernfs_dir_fops = { + .open = kernfs_fop_dir_open, .read = generic_read_dir, .iterate_shared = kernfs_fop_readdir, .release = kernfs_dir_fop_release,
Since down_read can block, use the _trylock variant if NOWAIT variant has been requested. (can probably do a little bit better style-wise) Signed-off-by: Dominique Martinet <asmadeus@codewreck.org> --- fs/kernfs/dir.c | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-)