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@xxxxxxx> --- fs/fuse/dev.c | 4 ++-- fs/fuse/dir.c | 2 +- fs/fuse/fuse_i.h | 11 +++++++++-- fs/fuse/inode.c | 8 ++++++++ 4 files changed, 20 insertions(+), 5 deletions(-) diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c index c979ce93685f8338301a094ac513c607f44ba572..3b4bdff84e534be8b1ce4a970e841b6a362ef176 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -1538,7 +1538,7 @@ 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; @@ -1587,7 +1587,7 @@ 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; diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c index 494ac372ace07ab4ea06c13a404ecc1d2ccb4f23..42db112e052f0c26d1ba9973b033b1c7cd822359 100644 --- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -371,7 +371,7 @@ 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; diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h index 74744c6f286003251564d1235f4d2ca8654d661b..5ce19bc6871291eeaa4c4af4ea935d4de80e8a00 100644 --- a/fs/fuse/fuse_i.h +++ b/fs/fuse/fuse_i.h @@ -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 @@ -893,6 +897,9 @@ 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 *); diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c index 3ce4f4e81d09e867c3a7db7b1dbb819f88ed34ef..4d61dacedf6a1684eb5dc39a6f56ded0ca4c1fe4 100644 --- a/fs/fuse/inode.c +++ b/fs/fuse/inode.c @@ -978,6 +978,7 @@ 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; if (IS_ENABLED(CONFIG_FUSE_PASSTHROUGH)) fuse_backing_files_init(fc); @@ -1335,6 +1336,13 @@ 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 && -- 2.43.0
