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fuse: Increase FUSE_NAME_MAX to PATH_MAX

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Our file system has a translation capability for S3-to-posix.
The current value of 1kiB is enough to cover S3 keys, but
does not allow encoding of %xx escape characters.
The limit is increased to (PATH_MAX - 1), as we need
3 x 1024 and that is close to PATH_MAX (4kB) already.
-1 is used as the terminating null is not included in the
length calculation.

Testing large file names was hard with libfuse/example file systems,
so I created a new memfs that does not have a 255 file name length
limitation.
https://github.com/libfuse/libfuse/pull/1077

The connection is initialized with FUSE_NAME_LOW_MAX, which
is set to the previous value of FUSE_NAME_MAX of 1024. With
FUSE_MIN_READ_BUFFER of 8192 that is enough for two file names
+ fuse headers.
When FUSE_INIT reply sets max_pages to a value > 1 we know
that fuse daemon supports request buffers of at least 2 pages
(+ header) and can therefore hold 2 x PATH_MAX file names - operations
like rename or link that need two file names are no issue then.

Signed-off-by: Bernd Schubert <bschubert@ddn.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
Bernd Schubert 2024-12-16 22:14:07 +01:00 committed by Miklos Szeredi
parent 2412085da3
commit 27992ef807
4 changed files with 20 additions and 5 deletions
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4
fs/fuse/dev.c
View File

@ -1657,7 +1657,7 @@ static int fuse_notify_inval_entry(struct fuse_conn *fc, unsigned int size,
goto err;
err = -ENAMETOOLONG;
if (outarg.namelen > FUSE_NAME_MAX)
if (outarg.namelen > fc->name_max)
goto err;
err = -EINVAL;
@ -1706,7 +1706,7 @@ static int fuse_notify_delete(struct fuse_conn *fc, unsigned int size,
goto err;
err = -ENAMETOOLONG;
if (outarg.namelen > FUSE_NAME_MAX)
if (outarg.namelen > fc->name_max)
goto err;
err = -EINVAL;

2
fs/fuse/dir.c
View File

@ -370,7 +370,7 @@ int fuse_lookup_name(struct super_block *sb, u64 nodeid, const struct qstr *name
*inode = NULL;
err = -ENAMETOOLONG;
if (name->len > FUSE_NAME_MAX)
if (name->len > fm->fc->name_max)
goto out;

11
fs/fuse/fuse_i.h
View File

@ -38,8 +38,12 @@
/** Bias for fi->writectr, meaning new writepages must not be sent */
#define FUSE_NOWRITE INT_MIN
/** It could be as large as PATH_MAX, but would that have any uses? */
#define FUSE_NAME_MAX 1024
/** Maximum length of a filename, not including terminating null */
/* maximum, small enough for FUSE_MIN_READ_BUFFER*/
#define FUSE_NAME_LOW_MAX 1024
/* maximum, but needs a request buffer > FUSE_MIN_READ_BUFFER */
#define FUSE_NAME_MAX (PATH_MAX - 1)
/** Number of dentries for each connection in the control filesystem */
#define FUSE_CTL_NUM_DENTRIES 5
@ -924,6 +928,9 @@ struct fuse_conn {
/** Version counter for evict inode */
atomic64_t evict_ctr;
/* maximum file name length */
u32 name_max;
/** Called on final put */
void (*release)(struct fuse_conn *);

8
fs/fuse/inode.c
View File

@ -982,6 +982,7 @@ void fuse_conn_init(struct fuse_conn *fc, struct fuse_mount *fm,
fc->user_ns = get_user_ns(user_ns);
fc->max_pages = FUSE_DEFAULT_MAX_PAGES_PER_REQ;
fc->max_pages_limit = fuse_max_pages_limit;
fc->name_max = FUSE_NAME_LOW_MAX;
fc->timeout.req_timeout = 0;
if (IS_ENABLED(CONFIG_FUSE_PASSTHROUGH))
@ -1373,6 +1374,13 @@ static void process_init_reply(struct fuse_mount *fm, struct fuse_args *args,
fc->max_pages =
min_t(unsigned int, fc->max_pages_limit,
max_t(unsigned int, arg->max_pages, 1));
/*
* PATH_MAX file names might need two pages for
* ops like rename
*/
if (fc->max_pages > 1)
fc->name_max = FUSE_NAME_MAX;
}
if (IS_ENABLED(CONFIG_FUSE_DAX)) {
if (flags & FUSE_MAP_ALIGNMENT &&