Change Details

First, struct file size is 80 bytes. There is an unused field at the end added in 2005: ``` ommit d2c9006fb572d62b689561459965dc5b05674746 Author: rwatson <rwatson@FreeBSD.org> Date: Wed Feb 2 10:55:32 2005 +0000 Add a place-holder f_label void * for a future struct label pointer required for the port of SELinux FLASK/TE to FreeBSD using the MAC Framework. diff --git a/sys/sys/file.h b/sys/sys/file.h index d3a9e9f2df1..febbf4d9d27 100644 --- a/sys/sys/file.h +++ b/sys/sys/file.h @@ -131,6 +131,7 @@ struct file { off_t f_nextoff; /* * offset of next expected read or write */ + void *f_label; /* Place-holder for struct label pointer. */ }; #endif /* _KERNEL */ ``` With this removed we can expand f_count from int to long with keeping the total size of 80 bytes (with 4 bytes of padding). Some fields can be made smaller but not enough to fit the extra 4 bytes. Motivation for the change is 2 fold: - range changes were added to account for legitimate overflows. 32-bit should be more than big enough for 32-bit machines, while 64-bit is of course way more than necessary to aovid overflows - the refcount API grows extra features which not only add work for this consumer (which does not use them), but also reduce the range With the switch to pure long-sized atomics full range is restored (and more) and there is less work to do.

First, struct file size is 80 bytes. There is an unused field at the end added in 2005: ``` ommit d2c9006fb572d62b689561459965dc5b05674746 Author: rwatson <rwatson@FreeBSD.org> Date: Wed Feb 2 10:55:32 2005 +0000 Add a place-holder f_label void * for a future struct label pointer required for the port of SELinux FLASK/TE to FreeBSD using the MAC Framework. diff --git a/sys/sys/file.h b/sys/sys/file.h index d3a9e9f2df1..febbf4d9d27 100644 --- a/sys/sys/file.h +++ b/sys/sys/file.h @@ -131,6 +131,7 @@ struct file { off_t f_nextoff; /* * offset of next expected read or write */ + void *f_label; /* Place-holder for struct label pointer. */ }; #endif /* _KERNEL */ ``` With this removed we can expand f_count from int to long while keeping the total size of 80 bytes (with 4 bytes of padding). Some fields can be made smaller but not enough to fit the extra 4 bytes. Motivation for the change is 2 fold: - range changes were added to account for legitimate overflows. 32-bit should be more than big enough for 32-bit machines, while 64-bit is of course way more than necessary to aovid overflows - the refcount API grows extra features which not only add work for this consumer (which does not use them), but also reduce the range With the switch to pure long-sized atomics full range is restored (and more) and there is less work to do.

First, struct file size is 80 bytes. There is an unused field at the end added in 2005: ``` ommit d2c9006fb572d62b689561459965dc5b05674746 Author: rwatson <rwatson@FreeBSD.org> Date: Wed Feb 2 10:55:32 2005 +0000 Add a place-holder f_label void * for a future struct label pointer required for the port of SELinux FLASK/TE to FreeBSD using the MAC Framework. diff --git a/sys/sys/file.h b/sys/sys/file.h index d3a9e9f2df1..febbf4d9d27 100644 --- a/sys/sys/file.h +++ b/sys/sys/file.h @@ -131,6 +131,7 @@ struct file { off_t f_nextoff; /* * offset of next expected read or write */ + void *f_label; /* Place-holder for struct label pointer. */ }; #endif /* _KERNEL */ ``` With this removed we can expand f_count from int to long withwhile keeping the total size of 80 bytes (with 4 bytes of padding). Some fields can be made smaller but not enough to fit the extra 4 bytes. Motivation for the change is 2 fold: - range changes were added to account for legitimate overflows. 32-bit should be more than big enough for 32-bit machines, while 64-bit is of course way more than necessary to aovid overflows - the refcount API grows extra features which not only add work for this consumer (which does not use them), but also reduce the range With the switch to pure long-sized atomics full range is restored (and more) and there is less work to do.