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d3916156 |
| 19-Dec-2023 |
Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz> |
kernel: relay: remove relay_file_splice_read dead code, doesn't work
Documentation/filesystems/relay.rst says to use return debugfs_create_file(filename, mode, parent, buf,
kernel: relay: remove relay_file_splice_read dead code, doesn't work
Documentation/filesystems/relay.rst says to use return debugfs_create_file(filename, mode, parent, buf, &relay_file_operations); and this is the only way relay_file_operations is used.
Thus: debugfs_create_file(&relay_file_operations) -> __debugfs_create_file(&debugfs_full_proxy_file_operations, &relay_file_operations) -> dentry{inode: {i_fop: &debugfs_full_proxy_file_operations}, d_fsdata: &relay_file_operations | DEBUGFS_FSDATA_IS_REAL_FOPS_BIT}
debugfs_full_proxy_file_operations.open is full_proxy_open, which extracts the &relay_file_operations from the dentry, and allocates via __full_proxy_fops_init() new fops, with trivial wrappers around release, llseek, read, write, poll, and unlocked_ioctl, then replaces the fops on the opened file therewith.
Naturally, all thusly-created debugfs files have .splice_read = NULL. This was introduced in commit 49d200deaa68 ("debugfs: prevent access to removed files' private data") from 2016-03-22.
AFAICT, relay_file_operations is the only struct file_operations used for debugfs which defines a .splice_read callback. Hooking it up with
> diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c > index 5063434be0fc..952fcf5b2afa 100644 > --- a/fs/debugfs/file.c > +++ b/fs/debugfs/file.c > @@ -328,6 +328,11 @@ FULL_PROXY_FUNC(write, ssize_t, filp, > loff_t *ppos), > ARGS(filp, buf, size, ppos)); > > +FULL_PROXY_FUNC(splice_read, long, in, > + PROTO(struct file *in, loff_t *ppos, struct pipe_inode_info *pipe, > + size_t len, unsigned int flags), > + ARGS(in, ppos, pipe, len, flags)); > + > FULL_PROXY_FUNC(unlocked_ioctl, long, filp, > PROTO(struct file *filp, unsigned int cmd, unsigned long arg), > ARGS(filp, cmd, arg)); > @@ -382,6 +387,8 @@ static void __full_proxy_fops_init(struct file_operations *proxy_fops, > proxy_fops->write = full_proxy_write; > if (real_fops->poll) > proxy_fops->poll = full_proxy_poll; > + if (real_fops->splice_read) > + proxy_fops->splice_read = full_proxy_splice_read; > if (real_fops->unlocked_ioctl) > proxy_fops->unlocked_ioctl = full_proxy_unlocked_ioctl; > }
shows it just doesn't work, and splicing always instantly returns empty (subsequent reads actually return the contents).
No-one noticed it became dead code in 2016, who knows if it worked back then. Clearly no-one cares; just delete it.
Link: https://lkml.kernel.org/r/dtexwpw6zcdx7dkx3xj5gyjp5syxmyretdcbcdtvrnukd4vvuh@tarta.nabijaczleweli.xyz Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Li kunyu <kunyu@nfschina.com> Cc: Mike Rapoport (IBM) <rppt@kernel.org> Cc: Rafael J. Wysocki <rafael@kernel.org> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Zhang Zhengming <zhang.zhengming@h3c.com> Cc: Zhao Lei <zhao_lei1@hoperun.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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6da2ec56 |
| 12-Jun-2018 |
Kees Cook <keescook@chromium.org> |
treewide: kmalloc() -> kmalloc_array()
The kmalloc() function has a 2-factor argument form, kmalloc_array(). This patch replaces cases of:
kmalloc(a * b, gfp)
with: kmalloc_array(a
treewide: kmalloc() -> kmalloc_array()
The kmalloc() function has a 2-factor argument form, kmalloc_array(). This patch replaces cases of:
kmalloc(a * b, gfp)
with: kmalloc_array(a * b, gfp)
as well as handling cases of:
kmalloc(a * b * c, gfp)
with:
kmalloc(array3_size(a, b, c), gfp)
as it's slightly less ugly than:
kmalloc_array(array_size(a, b), c, gfp)
This does, however, attempt to ignore constant size factors like:
kmalloc(4 * 1024, gfp)
though any constants defined via macros get caught up in the conversion.
Any factors with a sizeof() of "unsigned char", "char", and "u8" were dropped, since they're redundant.
The tools/ directory was manually excluded, since it has its own implementation of kmalloc().
The Coccinelle script used for this was:
// Fix redundant parens around sizeof(). @@ type TYPE; expression THING, E; @@
( kmalloc( - (sizeof(TYPE)) * E + sizeof(TYPE) * E , ...) | kmalloc( - (sizeof(THING)) * E + sizeof(THING) * E , ...) )
// Drop single-byte sizes and redundant parens. @@ expression COUNT; typedef u8; typedef __u8; @@
( kmalloc( - sizeof(u8) * (COUNT) + COUNT , ...) | kmalloc( - sizeof(__u8) * (COUNT) + COUNT , ...) | kmalloc( - sizeof(char) * (COUNT) + COUNT , ...) | kmalloc( - sizeof(unsigned char) * (COUNT) + COUNT , ...) | kmalloc( - sizeof(u8) * COUNT + COUNT , ...) | kmalloc( - sizeof(__u8) * COUNT + COUNT , ...) | kmalloc( - sizeof(char) * COUNT + COUNT , ...) | kmalloc( - sizeof(unsigned char) * COUNT + COUNT , ...) )
// 2-factor product with sizeof(type/expression) and identifier or constant. @@ type TYPE; expression THING; identifier COUNT_ID; constant COUNT_CONST; @@
( - kmalloc + kmalloc_array ( - sizeof(TYPE) * (COUNT_ID) + COUNT_ID, sizeof(TYPE) , ...) | - kmalloc + kmalloc_array ( - sizeof(TYPE) * COUNT_ID + COUNT_ID, sizeof(TYPE) , ...) | - kmalloc + kmalloc_array ( - sizeof(TYPE) * (COUNT_CONST) + COUNT_CONST, sizeof(TYPE) , ...) | - kmalloc + kmalloc_array ( - sizeof(TYPE) * COUNT_CONST + COUNT_CONST, sizeof(TYPE) , ...) | - kmalloc + kmalloc_array ( - sizeof(THING) * (COUNT_ID) + COUNT_ID, sizeof(THING) , ...) | - kmalloc + kmalloc_array ( - sizeof(THING) * COUNT_ID + COUNT_ID, sizeof(THING) , ...) | - kmalloc + kmalloc_array ( - sizeof(THING) * (COUNT_CONST) + COUNT_CONST, sizeof(THING) , ...) | - kmalloc + kmalloc_array ( - sizeof(THING) * COUNT_CONST + COUNT_CONST, sizeof(THING) , ...) )
// 2-factor product, only identifiers. @@ identifier SIZE, COUNT; @@
- kmalloc + kmalloc_array ( - SIZE * COUNT + COUNT, SIZE , ...)
// 3-factor product with 1 sizeof(type) or sizeof(expression), with // redundant parens removed. @@ expression THING; identifier STRIDE, COUNT; type TYPE; @@
( kmalloc( - sizeof(TYPE) * (COUNT) * (STRIDE) + array3_size(COUNT, STRIDE, sizeof(TYPE)) , ...) | kmalloc( - sizeof(TYPE) * (COUNT) * STRIDE + array3_size(COUNT, STRIDE, sizeof(TYPE)) , ...) | kmalloc( - sizeof(TYPE) * COUNT * (STRIDE) + array3_size(COUNT, STRIDE, sizeof(TYPE)) , ...) | kmalloc( - sizeof(TYPE) * COUNT * STRIDE + array3_size(COUNT, STRIDE, sizeof(TYPE)) , ...) | kmalloc( - sizeof(THING) * (COUNT) * (STRIDE) + array3_size(COUNT, STRIDE, sizeof(THING)) , ...) | kmalloc( - sizeof(THING) * (COUNT) * STRIDE + array3_size(COUNT, STRIDE, sizeof(THING)) , ...) | kmalloc( - sizeof(THING) * COUNT * (STRIDE) + array3_size(COUNT, STRIDE, sizeof(THING)) , ...) | kmalloc( - sizeof(THING) * COUNT * STRIDE + array3_size(COUNT, STRIDE, sizeof(THING)) , ...) )
// 3-factor product with 2 sizeof(variable), with redundant parens removed. @@ expression THING1, THING2; identifier COUNT; type TYPE1, TYPE2; @@
( kmalloc( - sizeof(TYPE1) * sizeof(TYPE2) * COUNT + array3_size(COUNT, sizeof(TYPE1), sizeof(TYPE2)) , ...) | kmalloc( - sizeof(TYPE1) * sizeof(THING2) * (COUNT) + array3_size(COUNT, sizeof(TYPE1), sizeof(TYPE2)) , ...) | kmalloc( - sizeof(THING1) * sizeof(THING2) * COUNT + array3_size(COUNT, sizeof(THING1), sizeof(THING2)) , ...) | kmalloc( - sizeof(THING1) * sizeof(THING2) * (COUNT) + array3_size(COUNT, sizeof(THING1), sizeof(THING2)) , ...) | kmalloc( - sizeof(TYPE1) * sizeof(THING2) * COUNT + array3_size(COUNT, sizeof(TYPE1), sizeof(THING2)) , ...) | kmalloc( - sizeof(TYPE1) * sizeof(THING2) * (COUNT) + array3_size(COUNT, sizeof(TYPE1), sizeof(THING2)) , ...) )
// 3-factor product, only identifiers, with redundant parens removed. @@ identifier STRIDE, SIZE, COUNT; @@
( kmalloc( - (COUNT) * STRIDE * SIZE + array3_size(COUNT, STRIDE, SIZE) , ...) | kmalloc( - COUNT * (STRIDE) * SIZE + array3_size(COUNT, STRIDE, SIZE) , ...) | kmalloc( - COUNT * STRIDE * (SIZE) + array3_size(COUNT, STRIDE, SIZE) , ...) | kmalloc( - (COUNT) * (STRIDE) * SIZE + array3_size(COUNT, STRIDE, SIZE) , ...) | kmalloc( - COUNT * (STRIDE) * (SIZE) + array3_size(COUNT, STRIDE, SIZE) , ...) | kmalloc( - (COUNT) * STRIDE * (SIZE) + array3_size(COUNT, STRIDE, SIZE) , ...) | kmalloc( - (COUNT) * (STRIDE) * (SIZE) + array3_size(COUNT, STRIDE, SIZE) , ...) | kmalloc( - COUNT * STRIDE * SIZE + array3_size(COUNT, STRIDE, SIZE) , ...) )
// Any remaining multi-factor products, first at least 3-factor products, // when they're not all constants... @@ expression E1, E2, E3; constant C1, C2, C3; @@
( kmalloc(C1 * C2 * C3, ...) | kmalloc( - (E1) * E2 * E3 + array3_size(E1, E2, E3) , ...) | kmalloc( - (E1) * (E2) * E3 + array3_size(E1, E2, E3) , ...) | kmalloc( - (E1) * (E2) * (E3) + array3_size(E1, E2, E3) , ...) | kmalloc( - E1 * E2 * E3 + array3_size(E1, E2, E3) , ...) )
// And then all remaining 2 factors products when they're not all constants, // keeping sizeof() as the second factor argument. @@ expression THING, E1, E2; type TYPE; constant C1, C2, C3; @@
( kmalloc(sizeof(THING) * C2, ...) | kmalloc(sizeof(TYPE) * C2, ...) | kmalloc(C1 * C2 * C3, ...) | kmalloc(C1 * C2, ...) | - kmalloc + kmalloc_array ( - sizeof(TYPE) * (E2) + E2, sizeof(TYPE) , ...) | - kmalloc + kmalloc_array ( - sizeof(TYPE) * E2 + E2, sizeof(TYPE) , ...) | - kmalloc + kmalloc_array ( - sizeof(THING) * (E2) + E2, sizeof(THING) , ...) | - kmalloc + kmalloc_array ( - sizeof(THING) * E2 + E2, sizeof(THING) , ...) | - kmalloc + kmalloc_array ( - (E1) * E2 + E1, E2 , ...) | - kmalloc + kmalloc_array ( - (E1) * (E2) + E1, E2 , ...) | - kmalloc + kmalloc_array ( - E1 * E2 + E1, E2 , ...) )
Signed-off-by: Kees Cook <keescook@chromium.org>
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