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| author | Andreas Gruenbacher <agruenba@redhat.com> | 2024-10-28 22:18:32 +0100 |
|---|---|---|
| committer | Andreas Gruenbacher <agruenba@redhat.com> | 2024-11-05 12:39:29 +0100 |
| commit | b6900ce15191ff9e219f1974b5db107ae02bb387 (patch) | |
| tree | def17bd4f5c5ef1c0d6f68bee3a98cd9e79a572a /fs/gfs2 | |
| parent | gfs2: gfs2_evict_inode clarification (diff) | |
| download | linux-b6900ce15191ff9e219f1974b5db107ae02bb387.tar.xz linux-b6900ce15191ff9e219f1974b5db107ae02bb387.zip | |
gfs2: Simplify DLM_LKF_QUECVT use
The DLM_LKF_QUECVT flag needs to be set for "upward" lock conversions to
ensure fairness, but setting it for "downward" lock conversions will
lead to a failure. The flag is currently set based on the GLF_BLOCKING
flag and it's not immediately obvious why this is correct. Simplify
things by figuring out if a lock conversion is "upward" by looking at
the before and after locking modes instead of relying on the
GLF_BLOCKING flag.
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Diffstat (limited to 'fs/gfs2')
| -rw-r--r-- | fs/gfs2/lock_dlm.c | 29 |
1 files changed, 25 insertions, 4 deletions
diff --git a/fs/gfs2/lock_dlm.c b/fs/gfs2/lock_dlm.c index fa5134df985f..58aeeae7ed8c 100644 --- a/fs/gfs2/lock_dlm.c +++ b/fs/gfs2/lock_dlm.c @@ -224,8 +224,21 @@ static int make_mode(struct gfs2_sbd *sdp, const unsigned int lmstate) return -1; } +/* Taken from fs/dlm/lock.c. */ + +static bool middle_conversion(int cur, int req) +{ + return (cur == DLM_LOCK_PR && req == DLM_LOCK_CW) || + (cur == DLM_LOCK_CW && req == DLM_LOCK_PR); +} + +static bool down_conversion(int cur, int req) +{ + return !middle_conversion(cur, req) && req < cur; +} + static u32 make_flags(struct gfs2_glock *gl, const unsigned int gfs_flags, - const int req) + const int cur, const int req) { u32 lkf = 0; @@ -251,7 +264,14 @@ static u32 make_flags(struct gfs2_glock *gl, const unsigned int gfs_flags, if (!test_bit(GLF_INITIAL, &gl->gl_flags)) { lkf |= DLM_LKF_CONVERT; - if (test_bit(GLF_BLOCKING, &gl->gl_flags)) + + /* + * The DLM_LKF_QUECVT flag needs to be set for "first come, + * first served" semantics, but it must only be set for + * "upward" lock conversions or else DLM will reject the + * request as invalid. + */ + if (!down_conversion(cur, req)) lkf |= DLM_LKF_QUECVT; } @@ -271,13 +291,14 @@ static int gdlm_lock(struct gfs2_glock *gl, unsigned int req_state, unsigned int flags) { struct lm_lockstruct *ls = &gl->gl_name.ln_sbd->sd_lockstruct; - int req; + int cur, req; u32 lkf; char strname[GDLM_STRNAME_BYTES] = ""; int error; + cur = make_mode(gl->gl_name.ln_sbd, gl->gl_state); req = make_mode(gl->gl_name.ln_sbd, req_state); - lkf = make_flags(gl, flags, req); + lkf = make_flags(gl, flags, cur, req); gfs2_glstats_inc(gl, GFS2_LKS_DCOUNT); gfs2_sbstats_inc(gl, GFS2_LKS_DCOUNT); if (test_bit(GLF_INITIAL, &gl->gl_flags)) { |