* [PATCH] tmpfs: Restore functionality of nr_inodes=0
@ 2020-09-02 3:57 Byron Stanoszek
2020-09-02 4:22 ` Hugh Dickins
2020-09-02 10:48 ` Chris Down
0 siblings, 2 replies; 3+ messages in thread
From: Byron Stanoszek @ 2020-09-02 3:57 UTC (permalink / raw)
To: Hugh Dickins, Andrew Morton, linux-mm, linux-kernel
Cc: Byron Stanoszek, Chris Down
Commit e809d5f0b5c9 ("tmpfs: per-superblock i_ino support") made changes to
shmem_reserve_inode() in mm/shmem.c, however the original test for
(sbinfo->max_inodes) got dropped. This causes mounting tmpfs with option
nr_inodes=0 to fail:
# mount -ttmpfs -onr_inodes=0 none /ext0
mount: /ext0: mount(2) system call failed: Cannot allocate memory.
This patch restores the nr_inodes=0 functionality.
Fixes: e809d5f0b5c9 ("tmpfs: per-superblock i_ino support")
Cc: Chris Down <chris@chrisdown.name>
Signed-off-by: Byron Stanoszek <gandalf@winds.org>
---
mm/shmem.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/mm/shmem.c b/mm/shmem.c
index 271548ca20f3..8e2b35ba93ad 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -279,11 +279,13 @@ static int shmem_reserve_inode(struct super_block *sb, ino_t *inop)
if (!(sb->s_flags & SB_KERNMOUNT)) {
spin_lock(&sbinfo->stat_lock);
- if (!sbinfo->free_inodes) {
- spin_unlock(&sbinfo->stat_lock);
- return -ENOSPC;
+ if (sbinfo->max_inodes) {
+ if (!sbinfo->free_inodes) {
+ spin_unlock(&sbinfo->stat_lock);
+ return -ENOSPC;
+ }
+ sbinfo->free_inodes--;
}
- sbinfo->free_inodes--;
if (inop) {
ino = sbinfo->next_ino++;
if (unlikely(is_zero_ino(ino)))
--
2.28.0
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] tmpfs: Restore functionality of nr_inodes=0
2020-09-02 3:57 [PATCH] tmpfs: Restore functionality of nr_inodes=0 Byron Stanoszek
@ 2020-09-02 4:22 ` Hugh Dickins
2020-09-02 10:48 ` Chris Down
1 sibling, 0 replies; 3+ messages in thread
From: Hugh Dickins @ 2020-09-02 4:22 UTC (permalink / raw)
To: Byron Stanoszek
Cc: Hugh Dickins, Andrew Morton, linux-mm, linux-kernel, Chris Down
On Tue, 1 Sep 2020, Byron Stanoszek wrote:
> Commit e809d5f0b5c9 ("tmpfs: per-superblock i_ino support") made changes to
> shmem_reserve_inode() in mm/shmem.c, however the original test for
> (sbinfo->max_inodes) got dropped. This causes mounting tmpfs with option
> nr_inodes=0 to fail:
>
> # mount -ttmpfs -onr_inodes=0 none /ext0
> mount: /ext0: mount(2) system call failed: Cannot allocate memory.
>
> This patch restores the nr_inodes=0 functionality.
>
> Fixes: e809d5f0b5c9 ("tmpfs: per-superblock i_ino support")
> Cc: Chris Down <chris@chrisdown.name>
> Signed-off-by: Byron Stanoszek <gandalf@winds.org>
Yikes, thank you Byron, very bad of me not to have spotted that:
Acked-by: Hugh Dickins <hughd@google.com>
I've taken a quick look to see how I missed it: yes, I'd compared
against my own tree, knew I had to come back here sometime to replace
the SB_KERNMOUNT test by a max_inodes test like I had, to restore the
performance of nr_inodes=0; but thought the SB_KERNMOUNT test was good
enough for now - without realizing the effect on the code below it. The
error does seem to be localized just to this block, yes. Many thanks.
> ---
> mm/shmem.c | 10 ++++++----
> 1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 271548ca20f3..8e2b35ba93ad 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -279,11 +279,13 @@ static int shmem_reserve_inode(struct super_block *sb, ino_t *inop)
>
> if (!(sb->s_flags & SB_KERNMOUNT)) {
> spin_lock(&sbinfo->stat_lock);
> - if (!sbinfo->free_inodes) {
> - spin_unlock(&sbinfo->stat_lock);
> - return -ENOSPC;
> + if (sbinfo->max_inodes) {
> + if (!sbinfo->free_inodes) {
> + spin_unlock(&sbinfo->stat_lock);
> + return -ENOSPC;
> + }
> + sbinfo->free_inodes--;
> }
> - sbinfo->free_inodes--;
> if (inop) {
> ino = sbinfo->next_ino++;
> if (unlikely(is_zero_ino(ino)))
> --
> 2.28.0
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] tmpfs: Restore functionality of nr_inodes=0
2020-09-02 3:57 [PATCH] tmpfs: Restore functionality of nr_inodes=0 Byron Stanoszek
2020-09-02 4:22 ` Hugh Dickins
@ 2020-09-02 10:48 ` Chris Down
1 sibling, 0 replies; 3+ messages in thread
From: Chris Down @ 2020-09-02 10:48 UTC (permalink / raw)
To: Byron Stanoszek; +Cc: Hugh Dickins, Andrew Morton, linux-mm, linux-kernel
Byron Stanoszek writes:
>Commit e809d5f0b5c9 ("tmpfs: per-superblock i_ino support") made changes to
>shmem_reserve_inode() in mm/shmem.c, however the original test for
>(sbinfo->max_inodes) got dropped. This causes mounting tmpfs with option
>nr_inodes=0 to fail:
>
> # mount -ttmpfs -onr_inodes=0 none /ext0
> mount: /ext0: mount(2) system call failed: Cannot allocate memory.
>
>This patch restores the nr_inodes=0 functionality.
>
>Fixes: e809d5f0b5c9 ("tmpfs: per-superblock i_ino support")
>Cc: Chris Down <chris@chrisdown.name>
>Signed-off-by: Byron Stanoszek <gandalf@winds.org>
Acked-by: Chris Down <chris@chrisdown.name>
Thanks, good catch.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2020-09-02 4:22 ` Hugh Dickins
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